| Message ID | 1475019532-16876-3-git-send-email-roderick@gaikai.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Sep 27, 2016 at 4:38 PM, Roderick Colenbrander <roderick@gaikai.com> wrote: > From: Roderick Colenbrander <roderick.colenbrander@sony.com> > > This patch introduces new axes for acceleration and angular velocity. > David Herrmann's work served as a base, but we extended the specification > with various changes inspired by real devices and challenges we see > when doing motion tracking. > > - Changed unit of acceleration to G instead of m/s^2. We felt that m/s^2 > is not the appropriate unit to return, because accelerometers are most > often calibrated based on gravity. They return values in multiples of > G and since we don't know the device location on earth, we should not > blindly multiply by '9.8' for accuracy reasons. Such conversion is left > to userspace. > - Resolution field is used for acceleration and gyro to report precision. > The previous spec, specified to map 1 unit to e.g. 0.001 deg/s or 0.001 m/s^2. > This is of course simpler for applications, but unit definition is a bit > arbitrary. Previous axes definitions used the resolution field, which > felt more consistent. > - Added section on timestamps, which are important for accurate motion > tracking purposes. The use of MSC_TIMESTAMP was recommended in this > situation to get access to the hardware timestamp if available. > - Changed motion axes to be defined as a right-handed coordinate system. > Due to this change the gyro vectors are now defined as counter-clockwise. > The overall changes makes the definitions consistent with computer graphics. > > [PATCH 4/4] Input: add motion-tracking ABS_* bits and docs > David Herrmann <dh.herrmann@gmail.com> > Tue Dec 17 07:48:54 PST 2013 > > Motion sensors are getting quite common in mobile devices. To avoid > returning accelerometer data via ABS_X/Y/Z and irritating the Xorg > mouse-driver, this adds separate ABS_* bits for that. We have IIO for motions sensors that are not strictly human input devices; I believe there is also IIO->input bridge where generic IIO sensors could be mapped to input device if they are supposed to be used as such in given product. > > This is needed if gaming devices want to report their normal data plus > accelerometer/gyro data. Usually, ABS_X/Y are already used by analog > sticks, so need separate definitions, anyway. I am not sure if this direction is sustainable. We can't keep adding more and more ABS axes every time we add another control to something that is basically a composite device. What if you add another stick? Magnetometer? Some other sensor? I think the only reasonable way it to come up with a notion of "composite" input device consisting of several event nodes and have userspace "assemble" it all together. > > Signed-off-by: David Herrmann <dh.herrmann@gmail.com> > Signed-off-by: Roderick Colenbrander <roderick.colenbrander@sony.com> > --- > Documentation/input/gamepad.txt | 9 +- > Documentation/input/motion-tracking.txt | 176 ++++++++++++++++++++++++++++++++ > include/uapi/linux/input-event-codes.h | 7 ++ > 3 files changed, 190 insertions(+), 2 deletions(-) > create mode 100644 Documentation/input/motion-tracking.txt > > diff --git a/Documentation/input/gamepad.txt b/Documentation/input/gamepad.txt > index 3f6d8a5..ed13782 100644 > --- a/Documentation/input/gamepad.txt > +++ b/Documentation/input/gamepad.txt > @@ -57,6 +57,9 @@ Most gamepads have the following features: > - Rumble > Many devices provide force-feedback features. But are mostly just > simple rumble motors. > + - Motion-tracking > + Gamepads may include motion-tracking sensors like accelerometers and > + gyroscopes. > > 3. Detection > ~~~~~~~~~~~~ > @@ -138,8 +141,6 @@ Triggers: > Upper trigger buttons are reported as BTN_TR or ABS_HAT1X (right) and BTN_TL > or ABS_HAT1Y (left). Lower trigger buttons are reported as BTN_TR2 or > ABS_HAT2X (right/ZR) and BTN_TL2 or ABS_HAT2Y (left/ZL). > - If only one trigger-button combination is present (upper+lower), they are > - reported as "right" triggers (BTN_TR/ABS_HAT1X). > (ABS trigger values start at 0, pressure is reported as positive values) > > Menu-Pad: > @@ -155,5 +156,9 @@ Menu-Pad: > Rumble: > Rumble is advertised as FF_RUMBLE. > > +Motion-tracking: > + Motion-tracking is defined in ./Documentation/input/motion-tracking.txt and > + gamepads shall comply to the rules defined there. > + > ---------------------------------------------------------------------------- > Written 2013 by David Herrmann <dh.herrmann@gmail.com> > diff --git a/Documentation/input/motion-tracking.txt b/Documentation/input/motion-tracking.txt > new file mode 100644 > index 0000000..d34a290 > --- /dev/null > +++ b/Documentation/input/motion-tracking.txt > @@ -0,0 +1,176 @@ > + Motion Tracking API > +---------------------------------------------------------------------------- > + > +1. Intro > +~~~~~~~~ > +Motion tracking devices produce device motion events generated from an > +accelerometer, gyroscope or compass. These data can be returned to user-space > +via input events. This document defines how these data are reported. > + > +2. Devices > +~~~~~~~~~~ > +In this document, a "device" is one of: > + - accelerometer > + - gyroscope > + - compass > + > +These devices returned their information via different APIs in the past. To > +unify them and define a common API, a set of input evdev codes was created. Old > +drivers might continue using their API, but developers are encouraged to use > +the input evdev API for new drivers. > + > +2.1 Axes > +~~~~~~~~ > +Movement data is usually returned as absolute data for the 3 axes of a device. > +In this context, the three axes are defined in a right-handed coordinate > +system as: > + - X: Axis goes from the left to the right side of the device > + - Y: Axis goes from the bottom to the top of the device > + - Z: Axis goes from the back to the front of the device > + > +The front of a device is the side faced to the user. For a mobile-phone it > +would be the screen. For devices without a screen, the top is usually the > +side with the most buttons on it. > + > + Example: Mobile-Phone > + +-------------------------------------------------------------------------+ > + | TOP | > + | | > + | | > + | +---------------------------+ | > + | |\ ________________________ \ .__ | > + | \ \ \ \ \ |\ | > + | \ \ \ __ \ \ \ RIGHT| > + | \ \ \ /| \ \ \__ | > + | \ \ \ __/ \ \ |\ | > + | \ \ \ /| \ \ \ (Y Axis) | > + | \ \ \ __/ (Z axis) \ \ \__ | > + | \ \ \ /| \ \ |\ | > + | LEFT \ \ \ / \ \ \ | > + | \ \ \ FRONT \ \ \ | > + | \ \ \ \ \ | > + | \ \ \_______________________\ \ | > + | \ \ ___ \ | > + | /\ \ \__\ \ | > + | __/ \ +---------------------------+ | > + | /| \|___________________________| | > + | / BACK | > + | (X axis) | > + | ------->------->------->-------> | > + | | > + | | > + | BOTTOM | > + +-------------------------------------------------------------------------+ > + > +Rotation-data is reported as counter-clockwise rotation on an axis when viewed > +from the top of the axis, as given by the right hand rule. For a given axis, > +the reported rotation would be: > + ____ > + //| > + // | (axis) > + // > + // > + . // __ > + / // /\ > + | // | > + \ // / (counter-clockwise rotation) > + *.___.* > + // > + // > + > +2.2 Calibration > +~~~~~~~~~~~~~~~ > +Motion sensors are often highly sensitive and need precise calibration. Users > +are advised to perform neutral-point calibration themselves or to implement a > +state-machine to normalize input data automatically. > + > +Kernel devices may perform their own calibration and/or normalization. However, > +this is usually sparse and, if implemented, transparent to the user. > + > +There is currently no way to feed calibration data into the kernel in a generic > +way. Proposals welcome! > + > +2.3 Units > +~~~~~~~~~ > +(NOTE: This section describes an experimental API. Currently, no device complies > +to these rules so this might change in the future.) > + > +Reported data shall be returned as: > + - Acceleration: 1/(input_absinfo.resolution) G > + - Rotation: 1/(input_absinfo.resolution) degree per second > + > +Acceleration is reported in units of G as opposed to m/s^2, because acceleration > +sensors internally work based on gravitation. Since the conversion to m/s^2 is > +location dependent, applications should either approximate the conversion > +factor as 9.8 m/s^2 or if more precision is desired obtain a scaling factor > +by other means e.g. GPS. > + > +However, for most devices the reported units are unknown (more precisely: no > +one has the time to measure them and figure them out). Therefore, user-space > +shall use abs-minimum and abs-maximum to calculate relative data and use that > +instead. Devices which return wrong units may be fixed in the future to comply > +to these rules. > + > +2.4 Timestamps > +~~~~~~~~~~~~~~ > +For motion tracking purposes the time delta between consecutive motion events > +is important for mathematical operations such as differentiation and integration. > +The time delta could be derived from the 'time' field in 'struct input_event' by > +subtracting the time between consecutive events. However, this timestamp may not > +provide enough accuracy depending on the use case, since it is based upon time of > +processing within the input layer versus time of arrival in the kernel or the > +time the hardware sent the data. There is often a small variable time difference > +between these. > + > +Optionally, hardware may provide a hardware timestamp produced at the time it > +sampled the motion sensors. This timestamp is is exposed through > +'MSC_TIMESTAMP' event, which provides timing information in microseconds. > +If available, MSC_TIMESTAMP is the recommended approach for calculation of time > +deltas. > + > +3.1 Accelerometer > +~~~~~~~~~~~~~~~~~ > +Accelerometers measure movement acceleration of devices. Any combination of the > +three available axes can be used. Usually, all three are supported. > + > +Data is provided as absolute acceleration. A positive integer defines the > +acceleration in the direction of an axis. A negative integer defines > +acceleration in the opposite direction. > + > +The evdev ABS codes used are: > + - ABS_ACCEL_X: X axis > + - ABS_ACCEL_Y: Y axis > + - ABS_ACCEL_Z: Z axis > + > +3.2 Gyroscope > +~~~~~~~~~~~~~ > +A gyroscope measures rotational speed (*not* acceleration!). Any combination of > +the three available axes can be used. Usually, all three are supported. > + > +Data is provided as absolute speed. A positive integer defines the rotational > +speed in counter-clockwise order around a given axis when viewed from the top of > +the axis. A negative integer defines it in clockwise order. > + > +The evdev ABS codes used are: > + - ABS_GYRO_X: X axis (also: Pitch) > + - ABS_GYRO_Y: Y axis (also: Roll) > + - ABS_GYRO_Z: Z axis (also: Azimuth/Yaw) > + > +3.3 Compass > +~~~~~~~~~~~ > +(NOTE: No compass device currently uses the evdev input subsystem. Thus, this > +API is only a proposal, it hasn't been implemented, yet.) > + > +A compass measures the ambient magnetic field of the three defined axes. This > +makes the data self-contained and independent of the current device position. > +Any combination of the three axes can be used. Usually all three are supported, > +otherwise, it's not really useful as a compass. > + > +Proposed evdev ABS codes are: > + - ABS_COMPASS_X: X axis > + - ABS_COMPASS_Y: Y axis > + - ABS_COMPASS_Z: Z axis > + > +---------------------------------------------------------------------------- > + (c) 2013 David Herrmann <dh.herrmann at gmail.com> > + (c) 2016 Roderick Colenbrander <roderick.colenbrander@sony.com> > diff --git a/include/uapi/linux/input-event-codes.h b/include/uapi/linux/input-event-codes.h > index 7bf2a2e..0cacfe7 100644 > --- a/include/uapi/linux/input-event-codes.h > +++ b/include/uapi/linux/input-event-codes.h > @@ -763,6 +763,13 @@ > #define ABS_MAX 0x3f > #define ABS_CNT (ABS_MAX+1) > > +#define ABS_GYRO_X 0x40 /* Gyroscope X axis */ > +#define ABS_GYRO_Y 0x41 /* Gyroscope Y axis */ > +#define ABS_GYRO_Z 0x42 /* Gyroscope Z axis */ > +#define ABS_ACCEL_X 0x43 /* Accelerometer X axis */ > +#define ABS_ACCEL_Y 0x44 /* Accelerometer Y axis */ > +#define ABS_ACCEL_Z 0x45 /* Accelerometer Z axis */ > + > /* > * Due to API restrictions the legacy evdev API only supports ABS values up to > * ABS_MAX/CNT. Use the extended *ABS2 ioctls to operate on the full range of > -- > 2.7.4 > Thanks.
On Wed, Sep 28, 2016 at 10:39 AM, Dmitry Torokhov <dmitry.torokhov@gmail.com> wrote: > > On Tue, Sep 27, 2016 at 4:38 PM, Roderick Colenbrander > <roderick@gaikai.com> wrote: > > From: Roderick Colenbrander <roderick.colenbrander@sony.com> > > > > This patch introduces new axes for acceleration and angular velocity. > > David Herrmann's work served as a base, but we extended the specification > > with various changes inspired by real devices and challenges we see > > when doing motion tracking. > > > > - Changed unit of acceleration to G instead of m/s^2. We felt that m/s^2 > > is not the appropriate unit to return, because accelerometers are most > > often calibrated based on gravity. They return values in multiples of > > G and since we don't know the device location on earth, we should not > > blindly multiply by '9.8' for accuracy reasons. Such conversion is left > > to userspace. > > - Resolution field is used for acceleration and gyro to report precision. > > The previous spec, specified to map 1 unit to e.g. 0.001 deg/s or 0.001 m/s^2. > > This is of course simpler for applications, but unit definition is a bit > > arbitrary. Previous axes definitions used the resolution field, which > > felt more consistent. > > - Added section on timestamps, which are important for accurate motion > > tracking purposes. The use of MSC_TIMESTAMP was recommended in this > > situation to get access to the hardware timestamp if available. > > - Changed motion axes to be defined as a right-handed coordinate system. > > Due to this change the gyro vectors are now defined as counter-clockwise. > > The overall changes makes the definitions consistent with computer graphics. > > > > [PATCH 4/4] Input: add motion-tracking ABS_* bits and docs > > David Herrmann <dh.herrmann@gmail.com> > > Tue Dec 17 07:48:54 PST 2013 > > > > Motion sensors are getting quite common in mobile devices. To avoid > > returning accelerometer data via ABS_X/Y/Z and irritating the Xorg > > mouse-driver, this adds separate ABS_* bits for that. > > We have IIO for motions sensors that are not strictly human input > devices; I believe there is also IIO->input bridge where generic IIO > sensors could be mapped to input device if they are supposed to be > used as such in given product. > If we decide to move forward in the direction proposed by this patch, the spec could be updated to limit the scope a bit or to make it wider. > > > > This is needed if gaming devices want to report their normal data plus > > accelerometer/gyro data. Usually, ABS_X/Y are already used by analog > > sticks, so need separate definitions, anyway. > > I am not sure if this direction is sustainable. We can't keep adding > more and more ABS axes every time we add another control to something > that is basically a composite device. What if you add another stick? > Magnetometer? Some other sensor? > > I think the only reasonable way it to come up with a notion of > "composite" input device consisting of several event nodes and have > userspace "assemble" it all together. > In our case we are interested in the motion functionality for some devices with drivers already in the kernel, which we want to extend over time with improved capabilities. I understand your concerns about the scalability of ABS axes in general. If someone were to come up with some crazy flight simulator joystick with many weird axes, do you then add an ABS_X2, ABS_X3 etcetera? Similar what if a controller for whatever reasons shipped with multiple gyroscopes, accelerometers, magnetic sensor, heartrate sensors etcetera? A composite device would on the other hand be more of a pain for the different userland APIs ranging from libinput, SDL2, Android and other embedded platforms. It would be quite an extensive change. How would they even do the stitching? You could handle this through sysfs (not my favorite way) or maybe have a notion of a 'master' device being the current event node and some way to enumerate 'sensor' nodes or something. It ultimate won't be my call, but I find it hard to say whether such a potential big overhaul is warranted at this point. Thanks, Roderick > > > > Signed-off-by: David Herrmann <dh.herrmann@gmail.com> > > Signed-off-by: Roderick Colenbrander <roderick.colenbrander@sony.com> > > --- > > Documentation/input/gamepad.txt | 9 +- > > Documentation/input/motion-tracking.txt | 176 ++++++++++++++++++++++++++++++++ > > include/uapi/linux/input-event-codes.h | 7 ++ > > 3 files changed, 190 insertions(+), 2 deletions(-) > > create mode 100644 Documentation/input/motion-tracking.txt > > > > diff --git a/Documentation/input/gamepad.txt b/Documentation/input/gamepad.txt > > index 3f6d8a5..ed13782 100644 > > --- a/Documentation/input/gamepad.txt > > +++ b/Documentation/input/gamepad.txt > > @@ -57,6 +57,9 @@ Most gamepads have the following features: > > - Rumble > > Many devices provide force-feedback features. But are mostly just > > simple rumble motors. > > + - Motion-tracking > > + Gamepads may include motion-tracking sensors like accelerometers and > > + gyroscopes. > > > > 3. Detection > > ~~~~~~~~~~~~ > > @@ -138,8 +141,6 @@ Triggers: > > Upper trigger buttons are reported as BTN_TR or ABS_HAT1X (right) and BTN_TL > > or ABS_HAT1Y (left). Lower trigger buttons are reported as BTN_TR2 or > > ABS_HAT2X (right/ZR) and BTN_TL2 or ABS_HAT2Y (left/ZL). > > - If only one trigger-button combination is present (upper+lower), they are > > - reported as "right" triggers (BTN_TR/ABS_HAT1X). > > (ABS trigger values start at 0, pressure is reported as positive values) > > > > Menu-Pad: > > @@ -155,5 +156,9 @@ Menu-Pad: > > Rumble: > > Rumble is advertised as FF_RUMBLE. > > > > +Motion-tracking: > > + Motion-tracking is defined in ./Documentation/input/motion-tracking.txt and > > + gamepads shall comply to the rules defined there. > > + > > ---------------------------------------------------------------------------- > > Written 2013 by David Herrmann <dh.herrmann@gmail.com> > > diff --git a/Documentation/input/motion-tracking.txt b/Documentation/input/motion-tracking.txt > > new file mode 100644 > > index 0000000..d34a290 > > --- /dev/null > > +++ b/Documentation/input/motion-tracking.txt > > @@ -0,0 +1,176 @@ > > + Motion Tracking API > > +---------------------------------------------------------------------------- > > + > > +1. Intro > > +~~~~~~~~ > > +Motion tracking devices produce device motion events generated from an > > +accelerometer, gyroscope or compass. These data can be returned to user-space > > +via input events. This document defines how these data are reported. > > + > > +2. Devices > > +~~~~~~~~~~ > > +In this document, a "device" is one of: > > + - accelerometer > > + - gyroscope > > + - compass > > + > > +These devices returned their information via different APIs in the past. To > > +unify them and define a common API, a set of input evdev codes was created. Old > > +drivers might continue using their API, but developers are encouraged to use > > +the input evdev API for new drivers. > > + > > +2.1 Axes > > +~~~~~~~~ > > +Movement data is usually returned as absolute data for the 3 axes of a device. > > +In this context, the three axes are defined in a right-handed coordinate > > +system as: > > + - X: Axis goes from the left to the right side of the device > > + - Y: Axis goes from the bottom to the top of the device > > + - Z: Axis goes from the back to the front of the device > > + > > +The front of a device is the side faced to the user. For a mobile-phone it > > +would be the screen. For devices without a screen, the top is usually the > > +side with the most buttons on it. > > + > > + Example: Mobile-Phone > > + +-------------------------------------------------------------------------+ > > + | TOP | > > + | | > > + | | > > + | +---------------------------+ | > > + | |\ ________________________ \ .__ | > > + | \ \ \ \ \ |\ | > > + | \ \ \ __ \ \ \ RIGHT| > > + | \ \ \ /| \ \ \__ | > > + | \ \ \ __/ \ \ |\ | > > + | \ \ \ /| \ \ \ (Y Axis) | > > + | \ \ \ __/ (Z axis) \ \ \__ | > > + | \ \ \ /| \ \ |\ | > > + | LEFT \ \ \ / \ \ \ | > > + | \ \ \ FRONT \ \ \ | > > + | \ \ \ \ \ | > > + | \ \ \_______________________\ \ | > > + | \ \ ___ \ | > > + | /\ \ \__\ \ | > > + | __/ \ +---------------------------+ | > > + | /| \|___________________________| | > > + | / BACK | > > + | (X axis) | > > + | ------->------->------->-------> | > > + | | > > + | | > > + | BOTTOM | > > + +-------------------------------------------------------------------------+ > > + > > +Rotation-data is reported as counter-clockwise rotation on an axis when viewed > > +from the top of the axis, as given by the right hand rule. For a given axis, > > +the reported rotation would be: > > + ____ > > + //| > > + // | (axis) > > + // > > + // > > + . // __ > > + / // /\ > > + | // | > > + \ // / (counter-clockwise rotation) > > + *.___.* > > + // > > + // > > + > > +2.2 Calibration > > +~~~~~~~~~~~~~~~ > > +Motion sensors are often highly sensitive and need precise calibration. Users > > +are advised to perform neutral-point calibration themselves or to implement a > > +state-machine to normalize input data automatically. > > + > > +Kernel devices may perform their own calibration and/or normalization. However, > > +this is usually sparse and, if implemented, transparent to the user. > > + > > +There is currently no way to feed calibration data into the kernel in a generic > > +way. Proposals welcome! > > + > > +2.3 Units > > +~~~~~~~~~ > > +(NOTE: This section describes an experimental API. Currently, no device complies > > +to these rules so this might change in the future.) > > + > > +Reported data shall be returned as: > > + - Acceleration: 1/(input_absinfo.resolution) G > > + - Rotation: 1/(input_absinfo.resolution) degree per second > > + > > +Acceleration is reported in units of G as opposed to m/s^2, because acceleration > > +sensors internally work based on gravitation. Since the conversion to m/s^2 is > > +location dependent, applications should either approximate the conversion > > +factor as 9.8 m/s^2 or if more precision is desired obtain a scaling factor > > +by other means e.g. GPS. > > + > > +However, for most devices the reported units are unknown (more precisely: no > > +one has the time to measure them and figure them out). Therefore, user-space > > +shall use abs-minimum and abs-maximum to calculate relative data and use that > > +instead. Devices which return wrong units may be fixed in the future to comply > > +to these rules. > > + > > +2.4 Timestamps > > +~~~~~~~~~~~~~~ > > +For motion tracking purposes the time delta between consecutive motion events > > +is important for mathematical operations such as differentiation and integration. > > +The time delta could be derived from the 'time' field in 'struct input_event' by > > +subtracting the time between consecutive events. However, this timestamp may not > > +provide enough accuracy depending on the use case, since it is based upon time of > > +processing within the input layer versus time of arrival in the kernel or the > > +time the hardware sent the data. There is often a small variable time difference > > +between these. > > + > > +Optionally, hardware may provide a hardware timestamp produced at the time it > > +sampled the motion sensors. This timestamp is is exposed through > > +'MSC_TIMESTAMP' event, which provides timing information in microseconds. > > +If available, MSC_TIMESTAMP is the recommended approach for calculation of time > > +deltas. > > + > > +3.1 Accelerometer > > +~~~~~~~~~~~~~~~~~ > > +Accelerometers measure movement acceleration of devices. Any combination of the > > +three available axes can be used. Usually, all three are supported. > > + > > +Data is provided as absolute acceleration. A positive integer defines the > > +acceleration in the direction of an axis. A negative integer defines > > +acceleration in the opposite direction. > > + > > +The evdev ABS codes used are: > > + - ABS_ACCEL_X: X axis > > + - ABS_ACCEL_Y: Y axis > > + - ABS_ACCEL_Z: Z axis > > + > > +3.2 Gyroscope > > +~~~~~~~~~~~~~ > > +A gyroscope measures rotational speed (*not* acceleration!). Any combination of > > +the three available axes can be used. Usually, all three are supported. > > + > > +Data is provided as absolute speed. A positive integer defines the rotational > > +speed in counter-clockwise order around a given axis when viewed from the top of > > +the axis. A negative integer defines it in clockwise order. > > + > > +The evdev ABS codes used are: > > + - ABS_GYRO_X: X axis (also: Pitch) > > + - ABS_GYRO_Y: Y axis (also: Roll) > > + - ABS_GYRO_Z: Z axis (also: Azimuth/Yaw) > > + > > +3.3 Compass > > +~~~~~~~~~~~ > > +(NOTE: No compass device currently uses the evdev input subsystem. Thus, this > > +API is only a proposal, it hasn't been implemented, yet.) > > + > > +A compass measures the ambient magnetic field of the three defined axes. This > > +makes the data self-contained and independent of the current device position. > > +Any combination of the three axes can be used. Usually all three are supported, > > +otherwise, it's not really useful as a compass. > > + > > +Proposed evdev ABS codes are: > > + - ABS_COMPASS_X: X axis > > + - ABS_COMPASS_Y: Y axis > > + - ABS_COMPASS_Z: Z axis > > + > > +---------------------------------------------------------------------------- > > + (c) 2013 David Herrmann <dh.herrmann at gmail.com> > > + (c) 2016 Roderick Colenbrander <roderick.colenbrander@sony.com> > > diff --git a/include/uapi/linux/input-event-codes.h b/include/uapi/linux/input-event-codes.h > > index 7bf2a2e..0cacfe7 100644 > > --- a/include/uapi/linux/input-event-codes.h > > +++ b/include/uapi/linux/input-event-codes.h > > @@ -763,6 +763,13 @@ > > #define ABS_MAX 0x3f > > #define ABS_CNT (ABS_MAX+1) > > > > +#define ABS_GYRO_X 0x40 /* Gyroscope X axis */ > > +#define ABS_GYRO_Y 0x41 /* Gyroscope Y axis */ > > +#define ABS_GYRO_Z 0x42 /* Gyroscope Z axis */ > > +#define ABS_ACCEL_X 0x43 /* Accelerometer X axis */ > > +#define ABS_ACCEL_Y 0x44 /* Accelerometer Y axis */ > > +#define ABS_ACCEL_Z 0x45 /* Accelerometer Z axis */ > > + > > /* > > * Due to API restrictions the legacy evdev API only supports ABS values up to > > * ABS_MAX/CNT. Use the extended *ABS2 ioctls to operate on the full range of > > -- > > 2.7.4 > > > > Thanks. > > -- > Dmitry
On Sep 28 2016 or thereabouts, Roderick Colenbrander wrote: > On Wed, Sep 28, 2016 at 10:39 AM, Dmitry Torokhov > <dmitry.torokhov@gmail.com> wrote: > > > > On Tue, Sep 27, 2016 at 4:38 PM, Roderick Colenbrander > > <roderick@gaikai.com> wrote: > > > From: Roderick Colenbrander <roderick.colenbrander@sony.com> > > > > > > This patch introduces new axes for acceleration and angular velocity. > > > David Herrmann's work served as a base, but we extended the specification > > > with various changes inspired by real devices and challenges we see > > > when doing motion tracking. > > > > > > - Changed unit of acceleration to G instead of m/s^2. We felt that m/s^2 > > > is not the appropriate unit to return, because accelerometers are most > > > often calibrated based on gravity. They return values in multiples of > > > G and since we don't know the device location on earth, we should not > > > blindly multiply by '9.8' for accuracy reasons. Such conversion is left > > > to userspace. > > > - Resolution field is used for acceleration and gyro to report precision. > > > The previous spec, specified to map 1 unit to e.g. 0.001 deg/s or 0.001 m/s^2. > > > This is of course simpler for applications, but unit definition is a bit > > > arbitrary. Previous axes definitions used the resolution field, which > > > felt more consistent. > > > - Added section on timestamps, which are important for accurate motion > > > tracking purposes. The use of MSC_TIMESTAMP was recommended in this > > > situation to get access to the hardware timestamp if available. > > > - Changed motion axes to be defined as a right-handed coordinate system. > > > Due to this change the gyro vectors are now defined as counter-clockwise. > > > The overall changes makes the definitions consistent with computer graphics. > > > > > > [PATCH 4/4] Input: add motion-tracking ABS_* bits and docs > > > David Herrmann <dh.herrmann@gmail.com> > > > Tue Dec 17 07:48:54 PST 2013 > > > > > > Motion sensors are getting quite common in mobile devices. To avoid > > > returning accelerometer data via ABS_X/Y/Z and irritating the Xorg > > > mouse-driver, this adds separate ABS_* bits for that. > > > > We have IIO for motions sensors that are not strictly human input > > devices; I believe there is also IIO->input bridge where generic IIO > > sensors could be mapped to input device if they are supposed to be > > used as such in given product. > > > > If we decide to move forward in the direction proposed by this patch, > the spec could be updated > to limit the scope a bit or to make it wider. > > > > > > > > This is needed if gaming devices want to report their normal data plus > > > accelerometer/gyro data. Usually, ABS_X/Y are already used by analog > > > sticks, so need separate definitions, anyway. > > > > I am not sure if this direction is sustainable. We can't keep adding > > more and more ABS axes every time we add another control to something > > that is basically a composite device. What if you add another stick? > > Magnetometer? Some other sensor? > > > > I think the only reasonable way it to come up with a notion of > > "composite" input device consisting of several event nodes and have > > userspace "assemble" it all together. > > > > In our case we are interested in the motion functionality for some devices > with drivers already in the kernel, which we want to extend over time with > improved capabilities. > > I understand your concerns about the scalability of ABS axes in general. > If someone were to come up with some crazy flight simulator joystick with many > weird axes, do you then add an ABS_X2, ABS_X3 etcetera? Similar what if > a controller for whatever reasons shipped with multiple gyroscopes, > accelerometers, > magnetic sensor, heartrate sensors etcetera? > > A composite device would on the other hand be more of a pain for the different > userland APIs ranging from libinput, SDL2, Android and other embedded > platforms. It That's already what we are doing for Wacom tablets (and some other devices) both in the kernel and in libinput. Wacom digitizers are exposed through 3 different device on average, one for the pen, one for the touch and one for the buttons on the pad. Libinput then relies on the notion of device group (a udev property) which can be tweaked when the heuristic fails (through libwacom mainly). Basically, libinput is not much of an issue, especially because we ignore accel, gyro, and other weird axis, and because we already know how to group composite devices. For the others, yes, it'll be a pain. But only if there is an actual need of grouping. If the sensors are the ones of the phone itself, having one or several input nodes doesn't hurt that much. If the sensors are coming from gamepads, then yes, there is a need for grouping, but hopefully the device path should provide some good heuristic. > would be quite an extensive change. How would they even do the > stitching? You could > handle this through sysfs (not my favorite way) or maybe have a notion > of a 'master' > device being the current event node and some way to enumerate 'sensor' > nodes or something. A simple udev property solves most of the grouping issues (based on the sysfs path mostly). The thing is currently, we are aware that the situation is not satisfying, and we are seeing the limit of the ABS axis declarations. We can find solutions (or workarounds) that works well enough, and adding ABS_MAX2 might not be the best solution long term: especially because of the slotted protocol inside ABS that messes things quite a bit. If we were to expand to ABS_MAX2, in order to avoid conflicts with the slotted protocol, we would need to reserve quite a few axis after ABS_MAX for this purpose. But we can't say how many will be required. Cheers, Benjamin > > It ultimate won't be my call, but I find it hard to say whether such a > potential big overhaul > is warranted at this point. > > Thanks, > Roderick > > > > > > > > Signed-off-by: David Herrmann <dh.herrmann@gmail.com> > > > Signed-off-by: Roderick Colenbrander <roderick.colenbrander@sony.com> > > > --- > > > Documentation/input/gamepad.txt | 9 +- > > > Documentation/input/motion-tracking.txt | 176 ++++++++++++++++++++++++++++++++ > > > include/uapi/linux/input-event-codes.h | 7 ++ > > > 3 files changed, 190 insertions(+), 2 deletions(-) > > > create mode 100644 Documentation/input/motion-tracking.txt > > > > > > diff --git a/Documentation/input/gamepad.txt b/Documentation/input/gamepad.txt > > > index 3f6d8a5..ed13782 100644 > > > --- a/Documentation/input/gamepad.txt > > > +++ b/Documentation/input/gamepad.txt > > > @@ -57,6 +57,9 @@ Most gamepads have the following features: > > > - Rumble > > > Many devices provide force-feedback features. But are mostly just > > > simple rumble motors. > > > + - Motion-tracking > > > + Gamepads may include motion-tracking sensors like accelerometers and > > > + gyroscopes. > > > > > > 3. Detection > > > ~~~~~~~~~~~~ > > > @@ -138,8 +141,6 @@ Triggers: > > > Upper trigger buttons are reported as BTN_TR or ABS_HAT1X (right) and BTN_TL > > > or ABS_HAT1Y (left). Lower trigger buttons are reported as BTN_TR2 or > > > ABS_HAT2X (right/ZR) and BTN_TL2 or ABS_HAT2Y (left/ZL). > > > - If only one trigger-button combination is present (upper+lower), they are > > > - reported as "right" triggers (BTN_TR/ABS_HAT1X). > > > (ABS trigger values start at 0, pressure is reported as positive values) > > > > > > Menu-Pad: > > > @@ -155,5 +156,9 @@ Menu-Pad: > > > Rumble: > > > Rumble is advertised as FF_RUMBLE. > > > > > > +Motion-tracking: > > > + Motion-tracking is defined in ./Documentation/input/motion-tracking.txt and > > > + gamepads shall comply to the rules defined there. > > > + > > > ---------------------------------------------------------------------------- > > > Written 2013 by David Herrmann <dh.herrmann@gmail.com> > > > diff --git a/Documentation/input/motion-tracking.txt b/Documentation/input/motion-tracking.txt > > > new file mode 100644 > > > index 0000000..d34a290 > > > --- /dev/null > > > +++ b/Documentation/input/motion-tracking.txt > > > @@ -0,0 +1,176 @@ > > > + Motion Tracking API > > > +---------------------------------------------------------------------------- > > > + > > > +1. Intro > > > +~~~~~~~~ > > > +Motion tracking devices produce device motion events generated from an > > > +accelerometer, gyroscope or compass. These data can be returned to user-space > > > +via input events. This document defines how these data are reported. > > > + > > > +2. Devices > > > +~~~~~~~~~~ > > > +In this document, a "device" is one of: > > > + - accelerometer > > > + - gyroscope > > > + - compass > > > + > > > +These devices returned their information via different APIs in the past. To > > > +unify them and define a common API, a set of input evdev codes was created. Old > > > +drivers might continue using their API, but developers are encouraged to use > > > +the input evdev API for new drivers. > > > + > > > +2.1 Axes > > > +~~~~~~~~ > > > +Movement data is usually returned as absolute data for the 3 axes of a device. > > > +In this context, the three axes are defined in a right-handed coordinate > > > +system as: > > > + - X: Axis goes from the left to the right side of the device > > > + - Y: Axis goes from the bottom to the top of the device > > > + - Z: Axis goes from the back to the front of the device > > > + > > > +The front of a device is the side faced to the user. For a mobile-phone it > > > +would be the screen. For devices without a screen, the top is usually the > > > +side with the most buttons on it. > > > + > > > + Example: Mobile-Phone > > > + +-------------------------------------------------------------------------+ > > > + | TOP | > > > + | | > > > + | | > > > + | +---------------------------+ | > > > + | |\ ________________________ \ .__ | > > > + | \ \ \ \ \ |\ | > > > + | \ \ \ __ \ \ \ RIGHT| > > > + | \ \ \ /| \ \ \__ | > > > + | \ \ \ __/ \ \ |\ | > > > + | \ \ \ /| \ \ \ (Y Axis) | > > > + | \ \ \ __/ (Z axis) \ \ \__ | > > > + | \ \ \ /| \ \ |\ | > > > + | LEFT \ \ \ / \ \ \ | > > > + | \ \ \ FRONT \ \ \ | > > > + | \ \ \ \ \ | > > > + | \ \ \_______________________\ \ | > > > + | \ \ ___ \ | > > > + | /\ \ \__\ \ | > > > + | __/ \ +---------------------------+ | > > > + | /| \|___________________________| | > > > + | / BACK | > > > + | (X axis) | > > > + | ------->------->------->-------> | > > > + | | > > > + | | > > > + | BOTTOM | > > > + +-------------------------------------------------------------------------+ > > > + > > > +Rotation-data is reported as counter-clockwise rotation on an axis when viewed > > > +from the top of the axis, as given by the right hand rule. For a given axis, > > > +the reported rotation would be: > > > + ____ > > > + //| > > > + // | (axis) > > > + // > > > + // > > > + . // __ > > > + / // /\ > > > + | // | > > > + \ // / (counter-clockwise rotation) > > > + *.___.* > > > + // > > > + // > > > + > > > +2.2 Calibration > > > +~~~~~~~~~~~~~~~ > > > +Motion sensors are often highly sensitive and need precise calibration. Users > > > +are advised to perform neutral-point calibration themselves or to implement a > > > +state-machine to normalize input data automatically. > > > + > > > +Kernel devices may perform their own calibration and/or normalization. However, > > > +this is usually sparse and, if implemented, transparent to the user. > > > + > > > +There is currently no way to feed calibration data into the kernel in a generic > > > +way. Proposals welcome! > > > + > > > +2.3 Units > > > +~~~~~~~~~ > > > +(NOTE: This section describes an experimental API. Currently, no device complies > > > +to these rules so this might change in the future.) > > > + > > > +Reported data shall be returned as: > > > + - Acceleration: 1/(input_absinfo.resolution) G > > > + - Rotation: 1/(input_absinfo.resolution) degree per second > > > + > > > +Acceleration is reported in units of G as opposed to m/s^2, because acceleration > > > +sensors internally work based on gravitation. Since the conversion to m/s^2 is > > > +location dependent, applications should either approximate the conversion > > > +factor as 9.8 m/s^2 or if more precision is desired obtain a scaling factor > > > +by other means e.g. GPS. > > > + > > > +However, for most devices the reported units are unknown (more precisely: no > > > +one has the time to measure them and figure them out). Therefore, user-space > > > +shall use abs-minimum and abs-maximum to calculate relative data and use that > > > +instead. Devices which return wrong units may be fixed in the future to comply > > > +to these rules. > > > + > > > +2.4 Timestamps > > > +~~~~~~~~~~~~~~ > > > +For motion tracking purposes the time delta between consecutive motion events > > > +is important for mathematical operations such as differentiation and integration. > > > +The time delta could be derived from the 'time' field in 'struct input_event' by > > > +subtracting the time between consecutive events. However, this timestamp may not > > > +provide enough accuracy depending on the use case, since it is based upon time of > > > +processing within the input layer versus time of arrival in the kernel or the > > > +time the hardware sent the data. There is often a small variable time difference > > > +between these. > > > + > > > +Optionally, hardware may provide a hardware timestamp produced at the time it > > > +sampled the motion sensors. This timestamp is is exposed through > > > +'MSC_TIMESTAMP' event, which provides timing information in microseconds. > > > +If available, MSC_TIMESTAMP is the recommended approach for calculation of time > > > +deltas. > > > + > > > +3.1 Accelerometer > > > +~~~~~~~~~~~~~~~~~ > > > +Accelerometers measure movement acceleration of devices. Any combination of the > > > +three available axes can be used. Usually, all three are supported. > > > + > > > +Data is provided as absolute acceleration. A positive integer defines the > > > +acceleration in the direction of an axis. A negative integer defines > > > +acceleration in the opposite direction. > > > + > > > +The evdev ABS codes used are: > > > + - ABS_ACCEL_X: X axis > > > + - ABS_ACCEL_Y: Y axis > > > + - ABS_ACCEL_Z: Z axis > > > + > > > +3.2 Gyroscope > > > +~~~~~~~~~~~~~ > > > +A gyroscope measures rotational speed (*not* acceleration!). Any combination of > > > +the three available axes can be used. Usually, all three are supported. > > > + > > > +Data is provided as absolute speed. A positive integer defines the rotational > > > +speed in counter-clockwise order around a given axis when viewed from the top of > > > +the axis. A negative integer defines it in clockwise order. > > > + > > > +The evdev ABS codes used are: > > > + - ABS_GYRO_X: X axis (also: Pitch) > > > + - ABS_GYRO_Y: Y axis (also: Roll) > > > + - ABS_GYRO_Z: Z axis (also: Azimuth/Yaw) > > > + > > > +3.3 Compass > > > +~~~~~~~~~~~ > > > +(NOTE: No compass device currently uses the evdev input subsystem. Thus, this > > > +API is only a proposal, it hasn't been implemented, yet.) > > > + > > > +A compass measures the ambient magnetic field of the three defined axes. This > > > +makes the data self-contained and independent of the current device position. > > > +Any combination of the three axes can be used. Usually all three are supported, > > > +otherwise, it's not really useful as a compass. > > > + > > > +Proposed evdev ABS codes are: > > > + - ABS_COMPASS_X: X axis > > > + - ABS_COMPASS_Y: Y axis > > > + - ABS_COMPASS_Z: Z axis > > > + > > > +---------------------------------------------------------------------------- > > > + (c) 2013 David Herrmann <dh.herrmann at gmail.com> > > > + (c) 2016 Roderick Colenbrander <roderick.colenbrander@sony.com> > > > diff --git a/include/uapi/linux/input-event-codes.h b/include/uapi/linux/input-event-codes.h > > > index 7bf2a2e..0cacfe7 100644 > > > --- a/include/uapi/linux/input-event-codes.h > > > +++ b/include/uapi/linux/input-event-codes.h > > > @@ -763,6 +763,13 @@ > > > #define ABS_MAX 0x3f > > > #define ABS_CNT (ABS_MAX+1) > > > > > > +#define ABS_GYRO_X 0x40 /* Gyroscope X axis */ > > > +#define ABS_GYRO_Y 0x41 /* Gyroscope Y axis */ > > > +#define ABS_GYRO_Z 0x42 /* Gyroscope Z axis */ > > > +#define ABS_ACCEL_X 0x43 /* Accelerometer X axis */ > > > +#define ABS_ACCEL_Y 0x44 /* Accelerometer Y axis */ > > > +#define ABS_ACCEL_Z 0x45 /* Accelerometer Z axis */ > > > + > > > /* > > > * Due to API restrictions the legacy evdev API only supports ABS values up to > > > * ABS_MAX/CNT. Use the extended *ABS2 ioctls to operate on the full range of > > > -- > > > 2.7.4 > > > > > > > Thanks. > > > > -- > > Dmitry > > > > > -- > Roderick Colenbrander > Senior Manager of Software Engineering > Gaikai, a Sony Computer Entertainment Company > roderick@gaikai.com -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 28.09.2016 18:39, Dmitry Torokhov wrote: > On Tue, Sep 27, 2016 at 4:38 PM, Roderick Colenbrander > <roderick@gaikai.com> wrote: >> From: Roderick Colenbrander <roderick.colenbrander@sony.com> >> >> This patch introduces new axes for acceleration and angular velocity. >> David Herrmann's work served as a base, but we extended the >> specification >> with various changes inspired by real devices and challenges we see >> when doing motion tracking. >> >> - Changed unit of acceleration to G instead of m/s^2. We felt that >> m/s^2 >> is not the appropriate unit to return, because accelerometers are >> most >> often calibrated based on gravity. I'd so like to believe they are referenced to a standard g rather than whatever is true at the plant. Almost no consumer parts are able to internally adjust their calibrations (or at least it's undocumented if they are). >> They return values in multiples of >> G and since we don't know the device location on earth, we should >> not >> blindly multiply by '9.8' for accuracy reasons. Such conversion is >> left >> to userspace. Hmm. If userspace is involved in trimming the readings, then the units don't matter. Ah well, not important really. However, there is a question of generalised interfaces. There are plenty of other devices (distance sensors etc) which measure in m. For IIO at least we have to support those as well so SI units are preferred. I remember having the same discussion long long ago! >> - Resolution field is used for acceleration and gyro to report >> precision. >> The previous spec, specified to map 1 unit to e.g. 0.001 deg/s or >> 0.001 m/s^2. >> This is of course simpler for applications, but unit definition is a >> bit >> arbitrary. Previous axes definitions used the resolution field, >> which >> felt more consistent. >> - Added section on timestamps, which are important for accurate motion >> tracking purposes. The use of MSC_TIMESTAMP was recommended in this >> situation to get access to the hardware timestamp if available. The moment you are into doing motion tracking I'm really thinking shoving it through input makes little sense... This is one of the main things IIO is set up to do... >> - Changed motion axes to be defined as a right-handed coordinate >> system. >> Due to this change the gyro vectors are now defined as >> counter-clockwise. >> The overall changes makes the definitions consistent with computer >> graphics. >> >> [PATCH 4/4] Input: add motion-tracking ABS_* bits and docs >> David Herrmann <dh.herrmann@gmail.com> >> Tue Dec 17 07:48:54 PST 2013 >> >> Motion sensors are getting quite common in mobile devices. To avoid >> returning accelerometer data via ABS_X/Y/Z and irritating the Xorg >> mouse-driver, this adds separate ABS_* bits for that. > > We have IIO for motions sensors that are not strictly human input > devices; I believe there is also IIO->input bridge where generic IIO > sensors could be mapped to input device if they are supposed to be > used as such in given product. Yeah, *looks guilty* I've been failing to actually submit the input bridge for a quite some time due to the open question of how the heck we describe the connectivity (device tree etc) after all the fuss over the hwmon bridge. Need to get this moving again - in principle it is very straight forward. The infrastructure is used for a few other purposes so is reasonably well tested. Basically there has been very push on this previously so good if someone wants to pick it up and push it forward. (basically I did it as a proof of concept years ago but didn't care that much as I don't have a screen on any of the boards I care about). > >> >> This is needed if gaming devices want to report their normal data plus >> accelerometer/gyro data. Usually, ABS_X/Y are already used by analog >> sticks, so need separate definitions, anyway. > > I am not sure if this direction is sustainable. We can't keep adding > more and more ABS axes every time we add another control to something > that is basically a composite device. What if you add another stick? > Magnetometer? Some other sensor? > > I think the only reasonable way it to come up with a notion of > "composite" input device consisting of several event nodes and have > userspace "assemble" it all together. That sounds sensible if we are going to pipe this stuff out to userspace. If the actual need is to do fusion on the various sensors then I'd be inclined to pull it from an IIO device directly then use uinput to push the fused result back in so that it emerges from input as one would expect a magic 'this is pose' data type. There is obviously the open question of how to describe the various axis if they don't make sense to be passed directly to input. So there are valid points raised by this email. > >> >> Signed-off-by: David Herrmann <dh.herrmann@gmail.com> >> Signed-off-by: Roderick Colenbrander <roderick.colenbrander@sony.com> >> --- >> Documentation/input/gamepad.txt | 9 +- >> Documentation/input/motion-tracking.txt | 176 >> ++++++++++++++++++++++++++++++++ >> include/uapi/linux/input-event-codes.h | 7 ++ >> 3 files changed, 190 insertions(+), 2 deletions(-) >> create mode 100644 Documentation/input/motion-tracking.txt >> >> diff --git a/Documentation/input/gamepad.txt >> b/Documentation/input/gamepad.txt >> index 3f6d8a5..ed13782 100644 >> --- a/Documentation/input/gamepad.txt >> +++ b/Documentation/input/gamepad.txt >> @@ -57,6 +57,9 @@ Most gamepads have the following features: >> - Rumble >> Many devices provide force-feedback features. But are mostly just >> simple rumble motors. >> + - Motion-tracking >> + Gamepads may include motion-tracking sensors like accelerometers >> and >> + gyroscopes. >> >> 3. Detection >> ~~~~~~~~~~~~ >> @@ -138,8 +141,6 @@ Triggers: >> Upper trigger buttons are reported as BTN_TR or ABS_HAT1X (right) >> and BTN_TL >> or ABS_HAT1Y (left). Lower trigger buttons are reported as BTN_TR2 >> or >> ABS_HAT2X (right/ZR) and BTN_TL2 or ABS_HAT2Y (left/ZL). >> - If only one trigger-button combination is present (upper+lower), >> they are >> - reported as "right" triggers (BTN_TR/ABS_HAT1X). >> (ABS trigger values start at 0, pressure is reported as positive >> values) >> >> Menu-Pad: >> @@ -155,5 +156,9 @@ Menu-Pad: >> Rumble: >> Rumble is advertised as FF_RUMBLE. >> >> +Motion-tracking: >> + Motion-tracking is defined in >> ./Documentation/input/motion-tracking.txt and >> + gamepads shall comply to the rules defined there. >> + >> >> ---------------------------------------------------------------------------- >> Written 2013 by David Herrmann <dh.herrmann@gmail.com> >> diff --git a/Documentation/input/motion-tracking.txt >> b/Documentation/input/motion-tracking.txt >> new file mode 100644 >> index 0000000..d34a290 >> --- /dev/null >> +++ b/Documentation/input/motion-tracking.txt >> @@ -0,0 +1,176 @@ >> + Motion Tracking API >> +---------------------------------------------------------------------------- >> + >> +1. Intro >> +~~~~~~~~ >> +Motion tracking devices produce device motion events generated from >> an >> +accelerometer, gyroscope or compass. These data can be returned to >> user-space >> +via input events. This document defines how these data are reported. >> + >> +2. Devices >> +~~~~~~~~~~ >> +In this document, a "device" is one of: >> + - accelerometer >> + - gyroscope >> + - compass >> + >> +These devices returned their information via different APIs in the >> past. To >> +unify them and define a common API, a set of input evdev codes was >> created. Old >> +drivers might continue using their API, but developers are encouraged >> to use >> +the input evdev API for new drivers. Agreed, it was a mess which is one of the reasons IIO came about. Another being that there are lots of usecases for these devices which have nothing to do with user input, where the filtering etc that occurs there is superfluous. >> + >> +2.1 Axes >> +~~~~~~~~ >> +Movement data is usually returned as absolute data for the 3 axes of >> a device. >> +In this context, the three axes are defined in a right-handed >> coordinate >> +system as: >> + - X: Axis goes from the left to the right side of the device >> + - Y: Axis goes from the bottom to the top of the device >> + - Z: Axis goes from the back to the front of the device >> + >> +The front of a device is the side faced to the user. For a >> mobile-phone it >> +would be the screen. For devices without a screen, the top is usually >> the >> +side with the most buttons on it. You need the means to describe a transformation from the chip to device space. It can be spectacularly non obvious. See the mounting matrix stuff we have in IIO. Doing the nasty floating point maths to fix this stuff is definitely a usespace job! >> + >> + Example: Mobile-Phone >> + >> +-------------------------------------------------------------------------+ >> + | TOP >> | >> + | >> | >> + | >> | >> + | +---------------------------+ >> | >> + | |\ ________________________ \ .__ >> | >> + | \ \ \ \ \ |\ >> | >> + | \ \ \ __ \ \ \ >> RIGHT| >> + | \ \ \ /| \ \ \__ >> | >> + | \ \ \ __/ \ \ |\ >> | >> + | \ \ \ /| \ \ \ (Y Axis) >> | >> + | \ \ \ __/ (Z axis) \ \ \__ >> | >> + | \ \ \ /| \ \ |\ >> | >> + | LEFT \ \ \ / \ \ \ >> | >> + | \ \ \ FRONT \ \ \ >> | >> + | \ \ \ \ \ >> | >> + | \ \ \_______________________\ \ >> | >> + | \ \ ___ \ >> | >> + | /\ \ \__\ \ >> | >> + | __/ \ +---------------------------+ >> | >> + | /| \|___________________________| >> | >> + | / BACK >> | >> + | (X axis) >> | >> + | ------->------->------->-------> >> | >> + | >> | >> + | >> | >> + | BOTTOM >> | >> + >> +-------------------------------------------------------------------------+ >> + >> +Rotation-data is reported as counter-clockwise rotation on an axis >> when viewed >> +from the top of the axis, as given by the right hand rule. For a >> given axis, >> +the reported rotation would be: >> + ____ >> + //| >> + // | (axis) >> + // >> + // >> + . // __ >> + / // /\ >> + | // | >> + \ // / (counter-clockwise >> rotation) >> + *.___.* >> + // >> + // >> + >> +2.2 Calibration >> +~~~~~~~~~~~~~~~ >> +Motion sensors are often highly sensitive and need precise >> calibration. Users >> +are advised to perform neutral-point calibration themselves or to >> implement a >> +state-machine to normalize input data automatically. >> + >> +Kernel devices may perform their own calibration and/or >> normalization. However, >> +this is usually sparse and, if implemented, transparent to the user. >> + >> +There is currently no way to feed calibration data into the kernel in >> a generic >> +way. Proposals welcome! There is in IIO and always has been. >> + >> +2.3 Units >> +~~~~~~~~~ >> +(NOTE: This section describes an experimental API. Currently, no >> device complies >> +to these rules so this might change in the future.) >> + >> +Reported data shall be returned as: >> + - Acceleration: 1/(input_absinfo.resolution) G >> + - Rotation: 1/(input_absinfo.resolution) degree per second >> + >> +Acceleration is reported in units of G as opposed to m/s^2, because >> acceleration >> +sensors internally work based on gravitation. No they don't. They work based on acceleration. Gravity just happens to cause acceleration. Please don't confuse this issue. Take a sensor calibrated in Cambridge UK (it's a bit of local joke round here and catches undergraduate physicists every year apparently) and carry it to almost anywhere else in the world and you'll find that the value goes up. >> Since the conversion to m/s^2 is >> +location dependent, applications should either approximate the >> conversion >> +factor as 9.8 m/s^2 or if more precision is desired obtain a scaling >> factor >> +by other means e.g. GPS. >> + >> +However, for most devices the reported units are unknown (more >> precisely: no >> +one has the time to measure them and figure them out). Therefore, >> user-space >> +shall use abs-minimum and abs-maximum to calculate relative data and >> use that >> +instead. Devices which return wrong units may be fixed in the future >> to comply >> +to these rules. Most devices they are known for, it's a characteristic of the relevant chip and typically factory calibrated (or based on design rules). >> + >> +2.4 Timestamps >> +~~~~~~~~~~~~~~ >> +For motion tracking purposes the time delta between consecutive >> motion events >> +is important for mathematical operations such as differentiation and >> integration. >> +The time delta could be derived from the 'time' field in 'struct >> input_event' by >> +subtracting the time between consecutive events. However, this >> timestamp may not >> +provide enough accuracy depending on the use case, since it is based >> upon time of >> +processing within the input layer versus time of arrival in the >> kernel or the >> +time the hardware sent the data. There is often a small variable time >> difference >> +between these. >> + >> +Optionally, hardware may provide a hardware timestamp produced at the >> time it >> +sampled the motion sensors. This timestamp is is exposed through >> +'MSC_TIMESTAMP' event, which provides timing information in >> microseconds. >> +If available, MSC_TIMESTAMP is the recommended approach for >> calculation of time >> +deltas. This is actually pretty unusual, but as you might expect we have supported it in IIO from the start. >> + >> +3.1 Accelerometer >> +~~~~~~~~~~~~~~~~~ >> +Accelerometers measure movement acceleration of devices. Any >> combination of the >> +three available axes can be used. Usually, all three are supported. >> + >> +Data is provided as absolute acceleration. A positive integer defines >> the >> +acceleration in the direction of an axis. A negative integer defines >> +acceleration in the opposite direction. >> + >> +The evdev ABS codes used are: >> + - ABS_ACCEL_X: X axis >> + - ABS_ACCEL_Y: Y axis >> + - ABS_ACCEL_Z: Z axis >> + >> +3.2 Gyroscope >> +~~~~~~~~~~~~~ >> +A gyroscope measures rotational speed (*not* acceleration!). Any >> combination of >> +the three available axes can be used. Usually, all three are >> supported. >> + >> +Data is provided as absolute speed. A positive integer defines the >> rotational >> +speed in counter-clockwise order around a given axis when viewed from >> the top of >> +the axis. A negative integer defines it in clockwise order. >> + >> +The evdev ABS codes used are: >> + - ABS_GYRO_X: X axis (also: Pitch) >> + - ABS_GYRO_Y: Y axis (also: Roll) >> + - ABS_GYRO_Z: Z axis (also: Azimuth/Yaw) >> + >> +3.3 Compass >> +~~~~~~~~~~~ >> +(NOTE: No compass device currently uses the evdev input subsystem. >> Thus, this >> +API is only a proposal, it hasn't been implemented, yet.) >> + >> +A compass measures the ambient magnetic field of the three defined >> axes. This >> +makes the data self-contained and independent of the current device >> position. >> +Any combination of the three axes can be used. Usually all three are >> supported, >> +otherwise, it's not really useful as a compass. >> + >> +Proposed evdev ABS codes are: >> + - ABS_COMPASS_X: X axis >> + - ABS_COMPASS_Y: Y axis >> + - ABS_COMPASS_Z: Z axis >> + >> +---------------------------------------------------------------------------- >> + (c) 2013 David Herrmann <dh.herrmann at gmail.com> >> + (c) 2016 Roderick Colenbrander <roderick.colenbrander@sony.com> >> diff --git a/include/uapi/linux/input-event-codes.h >> b/include/uapi/linux/input-event-codes.h >> index 7bf2a2e..0cacfe7 100644 >> --- a/include/uapi/linux/input-event-codes.h >> +++ b/include/uapi/linux/input-event-codes.h >> @@ -763,6 +763,13 @@ >> #define ABS_MAX 0x3f >> #define ABS_CNT (ABS_MAX+1) >> >> +#define ABS_GYRO_X 0x40 /* Gyroscope X axis */ >> +#define ABS_GYRO_Y 0x41 /* Gyroscope Y axis */ >> +#define ABS_GYRO_Z 0x42 /* Gyroscope Z axis */ >> +#define ABS_ACCEL_X 0x43 /* Accelerometer X axis */ >> +#define ABS_ACCEL_Y 0x44 /* Accelerometer Y axis */ >> +#define ABS_ACCEL_Z 0x45 /* Accelerometer Z axis */ >> + >> /* >> * Due to API restrictions the legacy evdev API only supports ABS >> values up to >> * ABS_MAX/CNT. Use the extended *ABS2 ioctls to operate on the full >> range of >> -- >> 2.7.4 >> > > Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Sep 29, 2016 at 1:55 AM, <jic23@jic23.retrosnub.co.uk> wrote: > On 28.09.2016 18:39, Dmitry Torokhov wrote: >> >> On Tue, Sep 27, 2016 at 4:38 PM, Roderick Colenbrander >> <roderick@gaikai.com> wrote: >>> >>> From: Roderick Colenbrander <roderick.colenbrander@sony.com> >>> >>> This patch introduces new axes for acceleration and angular velocity. >>> David Herrmann's work served as a base, but we extended the specification >>> with various changes inspired by real devices and challenges we see >>> when doing motion tracking. >>> >>> - Changed unit of acceleration to G instead of m/s^2. We felt that m/s^2 >>> is not the appropriate unit to return, because accelerometers are most >>> often calibrated based on gravity. > > I'd so like to believe they are referenced to a standard g rather than > whatever is true at the plant. Almost no consumer parts are able to > internally > adjust their calibrations (or at least it's undocumented if they are). Main motivation for g is that it is often easy to calibrate for. Typically there are registers with device specific constants for calibrated 1g values. At least in our case we are able to leverage these. >>> >>> They return values in multiples of >>> G and since we don't know the device location on earth, we should not >>> blindly multiply by '9.8' for accuracy reasons. Such conversion is left >>> to userspace. > > Hmm. If userspace is involved in trimming the readings, then the units don't > matter. > Ah well, not important really. However, there is a question of generalised > interfaces. There are plenty of other devices (distance sensors etc) which > measure > in m. For IIO at least we have to support those as well so SI units are > preferred. I remember having the same discussion long long ago! I think it really depends on the use case if trimming is needed. For various situations just 'g' is fine (it is better than raw values). Just the use case to go to m/s^2 is not possible at all in kernel (without passing parameters to the kernel module, which is undesired). Doing real calibration in user space would be a big challenge I think and not sure if it is easy to standardize. Some devices calibration is just about a multiplication and an offset, but other devices are non-linear or temperature dependent and needing frequent recalibration. It would best I think to basic calibration in kernel. >>> >>> - Resolution field is used for acceleration and gyro to report precision. >>> The previous spec, specified to map 1 unit to e.g. 0.001 deg/s or 0.001 >>> m/s^2. >>> This is of course simpler for applications, but unit definition is a >>> bit >>> arbitrary. Previous axes definitions used the resolution field, which >>> felt more consistent. >>> - Added section on timestamps, which are important for accurate motion >>> tracking purposes. The use of MSC_TIMESTAMP was recommended in this >>> situation to get access to the hardware timestamp if available. > > The moment you are into doing motion tracking I'm really thinking shoving it > through input makes little sense... This is one of the main things > IIO is set up to do... The devices we intend to support through this API are actual HID devices. They have the timestamp and motion sensor values within the same HID report as the other HID values come in (buttons, sticks, ..). That's basically the background on why we thought to add this to the spec, we noticed significant enough variation to the Linux timestamps. >>> - Changed motion axes to be defined as a right-handed coordinate system. >>> Due to this change the gyro vectors are now defined as >>> counter-clockwise. >>> The overall changes makes the definitions consistent with computer >>> graphics. >>> >>> [PATCH 4/4] Input: add motion-tracking ABS_* bits and docs >>> David Herrmann <dh.herrmann@gmail.com> >>> Tue Dec 17 07:48:54 PST 2013 >>> >>> Motion sensors are getting quite common in mobile devices. To avoid >>> returning accelerometer data via ABS_X/Y/Z and irritating the Xorg >>> mouse-driver, this adds separate ABS_* bits for that. >> >> >> We have IIO for motions sensors that are not strictly human input >> devices; I believe there is also IIO->input bridge where generic IIO >> sensors could be mapped to input device if they are supposed to be >> used as such in given product. > > Yeah, *looks guilty* I've been failing to actually submit the input > bridge for a quite some time due to the open question of how the heck > we describe the connectivity (device tree etc) after all the fuss > over the hwmon bridge. > > Need to get this moving again - in principle it is very straight forward. > The infrastructure is used for a few other purposes so is reasonably > well tested. > > Basically there has been very push on this previously so good > if someone wants to pick it up and push it forward. > > (basically I did it as a proof of concept years ago but didn't care > that much as I don't have a screen on any of the boards I care about). > >> >>> >>> This is needed if gaming devices want to report their normal data plus >>> accelerometer/gyro data. Usually, ABS_X/Y are already used by analog >>> sticks, so need separate definitions, anyway. >> >> >> I am not sure if this direction is sustainable. We can't keep adding >> more and more ABS axes every time we add another control to something >> that is basically a composite device. What if you add another stick? >> Magnetometer? Some other sensor? >> >> I think the only reasonable way it to come up with a notion of >> "composite" input device consisting of several event nodes and have >> userspace "assemble" it all together. > > That sounds sensible if we are going to pipe this stuff out to userspace. > > If the actual need is to do fusion on the various sensors then I'd be > inclined to pull it from an IIO device directly then use uinput to > push the fused result back in so that it emerges from input as one > would expect a magic 'this is pose' data type. > > There is obviously the open question of how to describe the various > axis if they don't make sense to be passed directly to input. > So there are valid points raised by this email. >> >>> >>> Signed-off-by: David Herrmann <dh.herrmann@gmail.com> >>> Signed-off-by: Roderick Colenbrander <roderick.colenbrander@sony.com> >>> --- >>> Documentation/input/gamepad.txt | 9 +- >>> Documentation/input/motion-tracking.txt | 176 >>> ++++++++++++++++++++++++++++++++ >>> include/uapi/linux/input-event-codes.h | 7 ++ >>> 3 files changed, 190 insertions(+), 2 deletions(-) >>> create mode 100644 Documentation/input/motion-tracking.txt >>> >>> diff --git a/Documentation/input/gamepad.txt >>> b/Documentation/input/gamepad.txt >>> index 3f6d8a5..ed13782 100644 >>> --- a/Documentation/input/gamepad.txt >>> +++ b/Documentation/input/gamepad.txt >>> @@ -57,6 +57,9 @@ Most gamepads have the following features: >>> - Rumble >>> Many devices provide force-feedback features. But are mostly just >>> simple rumble motors. >>> + - Motion-tracking >>> + Gamepads may include motion-tracking sensors like accelerometers and >>> + gyroscopes. >>> >>> 3. Detection >>> ~~~~~~~~~~~~ >>> @@ -138,8 +141,6 @@ Triggers: >>> Upper trigger buttons are reported as BTN_TR or ABS_HAT1X (right) and >>> BTN_TL >>> or ABS_HAT1Y (left). Lower trigger buttons are reported as BTN_TR2 or >>> ABS_HAT2X (right/ZR) and BTN_TL2 or ABS_HAT2Y (left/ZL). >>> - If only one trigger-button combination is present (upper+lower), they >>> are >>> - reported as "right" triggers (BTN_TR/ABS_HAT1X). >>> (ABS trigger values start at 0, pressure is reported as positive >>> values) >>> >>> Menu-Pad: >>> @@ -155,5 +156,9 @@ Menu-Pad: >>> Rumble: >>> Rumble is advertised as FF_RUMBLE. >>> >>> +Motion-tracking: >>> + Motion-tracking is defined in >>> ./Documentation/input/motion-tracking.txt and >>> + gamepads shall comply to the rules defined there. >>> + >>> >>> ---------------------------------------------------------------------------- >>> Written 2013 by David Herrmann <dh.herrmann@gmail.com> >>> diff --git a/Documentation/input/motion-tracking.txt >>> b/Documentation/input/motion-tracking.txt >>> new file mode 100644 >>> index 0000000..d34a290 >>> --- /dev/null >>> +++ b/Documentation/input/motion-tracking.txt >>> @@ -0,0 +1,176 @@ >>> + Motion Tracking API >>> >>> +---------------------------------------------------------------------------- >>> + >>> +1. Intro >>> +~~~~~~~~ >>> +Motion tracking devices produce device motion events generated from an >>> +accelerometer, gyroscope or compass. These data can be returned to >>> user-space >>> +via input events. This document defines how these data are reported. >>> + >>> +2. Devices >>> +~~~~~~~~~~ >>> +In this document, a "device" is one of: >>> + - accelerometer >>> + - gyroscope >>> + - compass >>> + >>> +These devices returned their information via different APIs in the past. >>> To >>> +unify them and define a common API, a set of input evdev codes was >>> created. Old >>> +drivers might continue using their API, but developers are encouraged to >>> use >>> +the input evdev API for new drivers. > > Agreed, it was a mess which is one of the reasons IIO came about. Another > being that there are lots of usecases for these devices which have nothing > to > do with user input, where the filtering etc that occurs there is > superfluous. > >>> + >>> +2.1 Axes >>> +~~~~~~~~ >>> +Movement data is usually returned as absolute data for the 3 axes of a >>> device. >>> +In this context, the three axes are defined in a right-handed coordinate >>> +system as: >>> + - X: Axis goes from the left to the right side of the device >>> + - Y: Axis goes from the bottom to the top of the device >>> + - Z: Axis goes from the back to the front of the device >>> + >>> +The front of a device is the side faced to the user. For a mobile-phone >>> it >>> +would be the screen. For devices without a screen, the top is usually >>> the >>> +side with the most buttons on it. > > You need the means to describe a transformation from the chip to device > space. > It can be spectacularly non obvious. See the mounting matrix stuff we have > in IIO. Doing the nasty floating point maths to fix this stuff is > definitely > a usespace job! > The consumer devices I worked with typically do this transformation on the HID device itself and give kind of transformed values to the driver, though values are not calibrated. I guess this is different for some other devices. >>> + >>> + Example: Mobile-Phone >>> + >>> +-------------------------------------------------------------------------+ >>> + | TOP >>> | >>> + | >>> | >>> + | >>> | >>> + | +---------------------------+ >>> | >>> + | |\ ________________________ \ .__ >>> | >>> + | \ \ \ \ \ |\ >>> | >>> + | \ \ \ __ \ \ \ >>> RIGHT| >>> + | \ \ \ /| \ \ \__ >>> | >>> + | \ \ \ __/ \ \ |\ >>> | >>> + | \ \ \ /| \ \ \ (Y Axis) >>> | >>> + | \ \ \ __/ (Z axis) \ \ \__ >>> | >>> + | \ \ \ /| \ \ |\ >>> | >>> + | LEFT \ \ \ / \ \ \ >>> | >>> + | \ \ \ FRONT \ \ \ >>> | >>> + | \ \ \ \ \ >>> | >>> + | \ \ \_______________________\ \ >>> | >>> + | \ \ ___ \ >>> | >>> + | /\ \ \__\ \ >>> | >>> + | __/ \ +---------------------------+ >>> | >>> + | /| \|___________________________| >>> | >>> + | / BACK >>> | >>> + | (X axis) >>> | >>> + | ------->------->------->-------> >>> | >>> + | >>> | >>> + | >>> | >>> + | BOTTOM >>> | >>> + >>> +-------------------------------------------------------------------------+ >>> + >>> +Rotation-data is reported as counter-clockwise rotation on an axis when >>> viewed >>> +from the top of the axis, as given by the right hand rule. For a given >>> axis, >>> +the reported rotation would be: >>> + ____ >>> + //| >>> + // | (axis) >>> + // >>> + // >>> + . // __ >>> + / // /\ >>> + | // | >>> + \ // / (counter-clockwise rotation) >>> + *.___.* >>> + // >>> + // >>> + >>> +2.2 Calibration >>> +~~~~~~~~~~~~~~~ >>> +Motion sensors are often highly sensitive and need precise calibration. >>> Users >>> +are advised to perform neutral-point calibration themselves or to >>> implement a >>> +state-machine to normalize input data automatically. >>> + >>> +Kernel devices may perform their own calibration and/or normalization. >>> However, >>> +this is usually sparse and, if implemented, transparent to the user. >>> + >>> +There is currently no way to feed calibration data into the kernel in a >>> generic >>> +way. Proposals welcome! > > There is in IIO and always has been. >>> >>> + >>> +2.3 Units >>> +~~~~~~~~~ >>> +(NOTE: This section describes an experimental API. Currently, no device >>> complies >>> +to these rules so this might change in the future.) >>> + >>> +Reported data shall be returned as: >>> + - Acceleration: 1/(input_absinfo.resolution) G >>> + - Rotation: 1/(input_absinfo.resolution) degree per second >>> + >>> +Acceleration is reported in units of G as opposed to m/s^2, because >>> acceleration >>> +sensors internally work based on gravitation. > > > No they don't. They work based on acceleration. Gravity just happens to > cause > acceleration. Please don't confuse this issue. Take a sensor calibrated in > Cambridge UK (it's a bit of local joke round here and catches undergraduate > physicists every year apparently) and carry it to almost anywhere else in > the > world and you'll find that the value goes up. > >>> Since the conversion to m/s^2 is >>> +location dependent, applications should either approximate the >>> conversion >>> +factor as 9.8 m/s^2 or if more precision is desired obtain a scaling >>> factor >>> +by other means e.g. GPS. >>> + >>> +However, for most devices the reported units are unknown (more >>> precisely: no >>> +one has the time to measure them and figure them out). Therefore, >>> user-space >>> +shall use abs-minimum and abs-maximum to calculate relative data and use >>> that >>> +instead. Devices which return wrong units may be fixed in the future to >>> comply >>> +to these rules. > > Most devices they are known for, it's a characteristic of the relevant chip > and > typically factory calibrated (or based on design rules). >>> >>> + >>> +2.4 Timestamps >>> +~~~~~~~~~~~~~~ >>> +For motion tracking purposes the time delta between consecutive motion >>> events >>> +is important for mathematical operations such as differentiation and >>> integration. >>> +The time delta could be derived from the 'time' field in 'struct >>> input_event' by >>> +subtracting the time between consecutive events. However, this timestamp >>> may not >>> +provide enough accuracy depending on the use case, since it is based >>> upon time of >>> +processing within the input layer versus time of arrival in the kernel >>> or the >>> +time the hardware sent the data. There is often a small variable time >>> difference >>> +between these. >>> + >>> +Optionally, hardware may provide a hardware timestamp produced at the >>> time it >>> +sampled the motion sensors. This timestamp is is exposed through >>> +'MSC_TIMESTAMP' event, which provides timing information in >>> microseconds. >>> +If available, MSC_TIMESTAMP is the recommended approach for calculation >>> of time >>> +deltas. > > This is actually pretty unusual, but as you might expect we have supported > it > in IIO from the start. For raw sensors I agree this may not always be around. At least in the consumer devices I have seen there is (and our devices have them as well) >>> + >>> +3.1 Accelerometer >>> +~~~~~~~~~~~~~~~~~ >>> +Accelerometers measure movement acceleration of devices. Any combination >>> of the >>> +three available axes can be used. Usually, all three are supported. >>> + >>> +Data is provided as absolute acceleration. A positive integer defines >>> the >>> +acceleration in the direction of an axis. A negative integer defines >>> +acceleration in the opposite direction. >>> + >>> +The evdev ABS codes used are: >>> + - ABS_ACCEL_X: X axis >>> + - ABS_ACCEL_Y: Y axis >>> + - ABS_ACCEL_Z: Z axis >>> + >>> +3.2 Gyroscope >>> +~~~~~~~~~~~~~ >>> +A gyroscope measures rotational speed (*not* acceleration!). Any >>> combination of >>> +the three available axes can be used. Usually, all three are supported. >>> + >>> +Data is provided as absolute speed. A positive integer defines the >>> rotational >>> +speed in counter-clockwise order around a given axis when viewed from >>> the top of >>> +the axis. A negative integer defines it in clockwise order. >>> + >>> +The evdev ABS codes used are: >>> + - ABS_GYRO_X: X axis (also: Pitch) >>> + - ABS_GYRO_Y: Y axis (also: Roll) >>> + - ABS_GYRO_Z: Z axis (also: Azimuth/Yaw) >>> + >>> +3.3 Compass >>> +~~~~~~~~~~~ >>> +(NOTE: No compass device currently uses the evdev input subsystem. Thus, >>> this >>> +API is only a proposal, it hasn't been implemented, yet.) >>> + >>> +A compass measures the ambient magnetic field of the three defined axes. >>> This >>> +makes the data self-contained and independent of the current device >>> position. >>> +Any combination of the three axes can be used. Usually all three are >>> supported, >>> +otherwise, it's not really useful as a compass. >>> + >>> +Proposed evdev ABS codes are: >>> + - ABS_COMPASS_X: X axis >>> + - ABS_COMPASS_Y: Y axis >>> + - ABS_COMPASS_Z: Z axis >>> + >>> >>> +---------------------------------------------------------------------------- >>> + (c) 2013 David Herrmann <dh.herrmann at gmail.com> >>> + (c) 2016 Roderick Colenbrander <roderick.colenbrander@sony.com> >>> diff --git a/include/uapi/linux/input-event-codes.h >>> b/include/uapi/linux/input-event-codes.h >>> index 7bf2a2e..0cacfe7 100644 >>> --- a/include/uapi/linux/input-event-codes.h >>> +++ b/include/uapi/linux/input-event-codes.h >>> @@ -763,6 +763,13 @@ >>> #define ABS_MAX 0x3f >>> #define ABS_CNT (ABS_MAX+1) >>> >>> +#define ABS_GYRO_X 0x40 /* Gyroscope X axis */ >>> +#define ABS_GYRO_Y 0x41 /* Gyroscope Y axis */ >>> +#define ABS_GYRO_Z 0x42 /* Gyroscope Z axis */ >>> +#define ABS_ACCEL_X 0x43 /* Accelerometer X axis */ >>> +#define ABS_ACCEL_Y 0x44 /* Accelerometer Y axis */ >>> +#define ABS_ACCEL_Z 0x45 /* Accelerometer Z axis */ >>> + >>> /* >>> * Due to API restrictions the legacy evdev API only supports ABS values >>> up to >>> * ABS_MAX/CNT. Use the extended *ABS2 ioctls to operate on the full >>> range of >>> -- >>> 2.7.4 >>> >> >> Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Sep 29, 2016 at 12:25 AM, Benjamin Tissoires <benjamin.tissoires@redhat.com> wrote: > > On Sep 28 2016 or thereabouts, Roderick Colenbrander wrote: > > On Wed, Sep 28, 2016 at 10:39 AM, Dmitry Torokhov > > <dmitry.torokhov@gmail.com> wrote: > > > > > > On Tue, Sep 27, 2016 at 4:38 PM, Roderick Colenbrander > > > <roderick@gaikai.com> wrote: > > > > From: Roderick Colenbrander <roderick.colenbrander@sony.com> > > > > > > > > This patch introduces new axes for acceleration and angular velocity. > > > > David Herrmann's work served as a base, but we extended the specification > > > > with various changes inspired by real devices and challenges we see > > > > when doing motion tracking. > > > > > > > > - Changed unit of acceleration to G instead of m/s^2. We felt that m/s^2 > > > > is not the appropriate unit to return, because accelerometers are most > > > > often calibrated based on gravity. They return values in multiples of > > > > G and since we don't know the device location on earth, we should not > > > > blindly multiply by '9.8' for accuracy reasons. Such conversion is left > > > > to userspace. > > > > - Resolution field is used for acceleration and gyro to report precision. > > > > The previous spec, specified to map 1 unit to e.g. 0.001 deg/s or 0.001 m/s^2. > > > > This is of course simpler for applications, but unit definition is a bit > > > > arbitrary. Previous axes definitions used the resolution field, which > > > > felt more consistent. > > > > - Added section on timestamps, which are important for accurate motion > > > > tracking purposes. The use of MSC_TIMESTAMP was recommended in this > > > > situation to get access to the hardware timestamp if available. > > > > - Changed motion axes to be defined as a right-handed coordinate system. > > > > Due to this change the gyro vectors are now defined as counter-clockwise. > > > > The overall changes makes the definitions consistent with computer graphics. > > > > > > > > [PATCH 4/4] Input: add motion-tracking ABS_* bits and docs > > > > David Herrmann <dh.herrmann@gmail.com> > > > > Tue Dec 17 07:48:54 PST 2013 > > > > > > > > Motion sensors are getting quite common in mobile devices. To avoid > > > > returning accelerometer data via ABS_X/Y/Z and irritating the Xorg > > > > mouse-driver, this adds separate ABS_* bits for that. > > > > > > We have IIO for motions sensors that are not strictly human input > > > devices; I believe there is also IIO->input bridge where generic IIO > > > sensors could be mapped to input device if they are supposed to be > > > used as such in given product. > > > > > > > If we decide to move forward in the direction proposed by this patch, > > the spec could be updated > > to limit the scope a bit or to make it wider. > > > > > > > > > > > > This is needed if gaming devices want to report their normal data plus > > > > accelerometer/gyro data. Usually, ABS_X/Y are already used by analog > > > > sticks, so need separate definitions, anyway. > > > > > > I am not sure if this direction is sustainable. We can't keep adding > > > more and more ABS axes every time we add another control to something > > > that is basically a composite device. What if you add another stick? > > > Magnetometer? Some other sensor? > > > > > > I think the only reasonable way it to come up with a notion of > > > "composite" input device consisting of several event nodes and have > > > userspace "assemble" it all together. > > > > > > > In our case we are interested in the motion functionality for some devices > > with drivers already in the kernel, which we want to extend over time with > > improved capabilities. > > > > I understand your concerns about the scalability of ABS axes in general. > > If someone were to come up with some crazy flight simulator joystick with many > > weird axes, do you then add an ABS_X2, ABS_X3 etcetera? Similar what if > > a controller for whatever reasons shipped with multiple gyroscopes, > > accelerometers, > > magnetic sensor, heartrate sensors etcetera? > > > > A composite device would on the other hand be more of a pain for the different > > userland APIs ranging from libinput, SDL2, Android and other embedded > > platforms. It > > That's already what we are doing for Wacom tablets (and some other > devices) both in the kernel and in libinput. Wacom digitizers are > exposed through 3 different device on average, one for the pen, one for > the touch and one for the buttons on the pad. Libinput then relies on > the notion of device group (a udev property) which can be tweaked when > the heuristic fails (through libwacom mainly). > > Basically, libinput is not much of an issue, especially because we > ignore accel, gyro, and other weird axis, and because we already know > how to group composite devices. > > For the others, yes, it'll be a pain. But only if there is an actual need of > grouping. If the sensors are the ones of the phone itself, having one or > several input nodes doesn't hurt that much. If the sensors are coming > from gamepads, then yes, there is a need for grouping, but hopefully the > device path should provide some good heuristic. > How are you currently ignoring accel, gyro and others axes? The main concern I have is how to express the axes and how does userspace detect these? One of the examples I saw is the Wii driver, which supports accel, gyro and others. It exposes both accel and gyro data through ABS_RX/_RY/_RZ and adds "Accelerometer" or "Motion Plus" to the name. In my opinion, applications shouldn't rely on string parsing for this stuff. Not sure if I agree with using axes which were originally intended for rotational exes for acceleration instead of just ABS_X/_Y/_Z, though for gyro they would make sense. On the other hand Wacom sets 'INPUT_PROP_ACCELEROMETER' and reports acceleration data through ABS_X/_Y/_Z. This feels more reasonable to me as originally ABS_X/_Y/_Z where meant for horizontal displacements. There are probably some other examples as well. I'm trying to figure what direction would make sense moving forward. I'm starting to accept the need for composite devices. Questions: - What axes to use for accel? Should this be X/Y/Z or RX/RY/RZ, as I showed there is no real standard. - What axes to use for gyro? I think we would need an additional INPUT_PROP_GYROSCOPE. For any of these axes should there be some sort of standard on increments per unit. Originally ABS_X apparently was in units/mm and ABS_RX in units/radian. Though most of the time actual units are unknown... but it is also a pain for applications to know about every device. > > would be quite an extensive change. How would they even do the > > stitching? You could > > handle this through sysfs (not my favorite way) or maybe have a notion > > of a 'master' > > device being the current event node and some way to enumerate 'sensor' > > nodes or something. > > A simple udev property solves most of the grouping issues (based on the > sysfs path mostly). > > The thing is currently, we are aware that the situation is not > satisfying, and we are seeing the limit of the ABS axis declarations. We > can find solutions (or workarounds) that works well enough, and adding > ABS_MAX2 might not be the best solution long term: especially because of > the slotted protocol inside ABS that messes things quite a bit. > > If we were to expand to ABS_MAX2, in order to avoid conflicts with the > slotted protocol, we would need to reserve quite a few axis after > ABS_MAX for this purpose. But we can't say how many will be required. > > Cheers, > Benjamin > -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Nov 07, 2016 at 07:24:15PM -0800, Roderick Colenbrander wrote: > On Thu, Sep 29, 2016 at 12:25 AM, Benjamin Tissoires > <benjamin.tissoires@redhat.com> wrote: > > > > On Sep 28 2016 or thereabouts, Roderick Colenbrander wrote: > > > On Wed, Sep 28, 2016 at 10:39 AM, Dmitry Torokhov > > > <dmitry.torokhov@gmail.com> wrote: > > > > > > > > On Tue, Sep 27, 2016 at 4:38 PM, Roderick Colenbrander > > > > <roderick@gaikai.com> wrote: > > > > > From: Roderick Colenbrander <roderick.colenbrander@sony.com> > > > > > > > > > > This patch introduces new axes for acceleration and angular velocity. > > > > > David Herrmann's work served as a base, but we extended the specification > > > > > with various changes inspired by real devices and challenges we see > > > > > when doing motion tracking. > > > > > > > > > > - Changed unit of acceleration to G instead of m/s^2. We felt that m/s^2 > > > > > is not the appropriate unit to return, because accelerometers are most > > > > > often calibrated based on gravity. They return values in multiples of > > > > > G and since we don't know the device location on earth, we should not > > > > > blindly multiply by '9.8' for accuracy reasons. Such conversion is left > > > > > to userspace. > > > > > - Resolution field is used for acceleration and gyro to report precision. > > > > > The previous spec, specified to map 1 unit to e.g. 0.001 deg/s or 0.001 m/s^2. > > > > > This is of course simpler for applications, but unit definition is a bit > > > > > arbitrary. Previous axes definitions used the resolution field, which > > > > > felt more consistent. > > > > > - Added section on timestamps, which are important for accurate motion > > > > > tracking purposes. The use of MSC_TIMESTAMP was recommended in this > > > > > situation to get access to the hardware timestamp if available. > > > > > - Changed motion axes to be defined as a right-handed coordinate system. > > > > > Due to this change the gyro vectors are now defined as counter-clockwise. > > > > > The overall changes makes the definitions consistent with computer graphics. > > > > > > > > > > [PATCH 4/4] Input: add motion-tracking ABS_* bits and docs > > > > > David Herrmann <dh.herrmann@gmail.com> > > > > > Tue Dec 17 07:48:54 PST 2013 > > > > > > > > > > Motion sensors are getting quite common in mobile devices. To avoid > > > > > returning accelerometer data via ABS_X/Y/Z and irritating the Xorg > > > > > mouse-driver, this adds separate ABS_* bits for that. > > > > > > > > We have IIO for motions sensors that are not strictly human input > > > > devices; I believe there is also IIO->input bridge where generic IIO > > > > sensors could be mapped to input device if they are supposed to be > > > > used as such in given product. > > > > > > > > > > If we decide to move forward in the direction proposed by this patch, > > > the spec could be updated > > > to limit the scope a bit or to make it wider. > > > > > > > > > > > > > > > > This is needed if gaming devices want to report their normal data plus > > > > > accelerometer/gyro data. Usually, ABS_X/Y are already used by analog > > > > > sticks, so need separate definitions, anyway. > > > > > > > > I am not sure if this direction is sustainable. We can't keep adding > > > > more and more ABS axes every time we add another control to something > > > > that is basically a composite device. What if you add another stick? > > > > Magnetometer? Some other sensor? > > > > > > > > I think the only reasonable way it to come up with a notion of > > > > "composite" input device consisting of several event nodes and have > > > > userspace "assemble" it all together. > > > > > > > > > > In our case we are interested in the motion functionality for some devices > > > with drivers already in the kernel, which we want to extend over time with > > > improved capabilities. > > > > > > I understand your concerns about the scalability of ABS axes in general. > > > If someone were to come up with some crazy flight simulator joystick with many > > > weird axes, do you then add an ABS_X2, ABS_X3 etcetera? Similar what if > > > a controller for whatever reasons shipped with multiple gyroscopes, > > > accelerometers, > > > magnetic sensor, heartrate sensors etcetera? > > > > > > A composite device would on the other hand be more of a pain for the different > > > userland APIs ranging from libinput, SDL2, Android and other embedded > > > platforms. It > > > > That's already what we are doing for Wacom tablets (and some other > > devices) both in the kernel and in libinput. Wacom digitizers are > > exposed through 3 different device on average, one for the pen, one for > > the touch and one for the buttons on the pad. Libinput then relies on > > the notion of device group (a udev property) which can be tweaked when > > the heuristic fails (through libwacom mainly). > > > > Basically, libinput is not much of an issue, especially because we > > ignore accel, gyro, and other weird axis, and because we already know > > how to group composite devices. > > > > For the others, yes, it'll be a pain. But only if there is an actual need of > > grouping. If the sensors are the ones of the phone itself, having one or > > several input nodes doesn't hurt that much. If the sensors are coming > > from gamepads, then yes, there is a need for grouping, but hopefully the > > device path should provide some good heuristic. > > > > How are you currently ignoring accel, gyro and others axes? The main > concern I have is how to express the axes and how does userspace > detect these? libinput supports traditional input devices only, so we can simply ignore anything that looks like an accelerometer, i.e. INPUT_PROP_ACCELEROMETER. it's that easy ;) > One of the examples I saw is the Wii driver, which supports accel, > gyro and others. It exposes both accel and gyro data through > ABS_RX/_RY/_RZ and adds "Accelerometer" or "Motion Plus" to the name. > In my opinion, applications shouldn't rely on string parsing for this > stuff. Not sure if I agree with using axes which were originally > intended for rotational exes for acceleration instead of just > ABS_X/_Y/_Z, though for gyro they would make sense. > > On the other hand Wacom sets 'INPUT_PROP_ACCELEROMETER' and reports > acceleration data through ABS_X/_Y/_Z. This feels more reasonable to > me as originally ABS_X/_Y/_Z where meant for horizontal displacements. > > There are probably some other examples as well. I'm trying to figure > what direction would make sense moving forward. I'm starting to accept > the need for composite devices. Questions: > - What axes to use for accel? Should this be X/Y/Z or RX/RY/RZ, as I > showed there is no real standard. please use x/y/z with the INPUT_PROP_ACCELEROMETER. See the doc for that property in Documentation/input/event-codes.txt The rx/ry/rz are historical baggage, let's not use that for new implementations. > - What axes to use for gyro? I think we would need an additional > INPUT_PROP_GYROSCOPE. I'd probably go for INPUT_PROP_ACCELEROMETER with rx/ry/rz set and documenting it as such, but not 100% sure here. > For any of these axes should there be some sort of standard on > increments per unit. Originally ABS_X apparently was in units/mm and > ABS_RX in units/radian. Though most of the time actual units are > unknown... but it is also a pain for applications to know about every > device. fwiw, ABS_X is still interpreted as units/mm for all flat devices. I'd consider anything else a bug. Cheers, Peter > > > would be quite an extensive change. How would they even do the > > > stitching? You could > > > handle this through sysfs (not my favorite way) or maybe have a notion > > > of a 'master' > > > device being the current event node and some way to enumerate 'sensor' > > > nodes or something. > > > > A simple udev property solves most of the grouping issues (based on the > > sysfs path mostly). > > > > The thing is currently, we are aware that the situation is not > > satisfying, and we are seeing the limit of the ABS axis declarations. We > > can find solutions (or workarounds) that works well enough, and adding > > ABS_MAX2 might not be the best solution long term: especially because of > > the slotted protocol inside ABS that messes things quite a bit. > > > > If we were to expand to ABS_MAX2, in order to avoid conflicts with the > > slotted protocol, we would need to reserve quite a few axis after > > ABS_MAX for this purpose. But we can't say how many will be required. > > > > Cheers, > > Benjamin > > -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/Documentation/input/gamepad.txt b/Documentation/input/gamepad.txt index 3f6d8a5..ed13782 100644 --- a/Documentation/input/gamepad.txt +++ b/Documentation/input/gamepad.txt @@ -57,6 +57,9 @@ Most gamepads have the following features: - Rumble Many devices provide force-feedback features. But are mostly just simple rumble motors. + - Motion-tracking + Gamepads may include motion-tracking sensors like accelerometers and + gyroscopes. 3. Detection ~~~~~~~~~~~~ @@ -138,8 +141,6 @@ Triggers: Upper trigger buttons are reported as BTN_TR or ABS_HAT1X (right) and BTN_TL or ABS_HAT1Y (left). Lower trigger buttons are reported as BTN_TR2 or ABS_HAT2X (right/ZR) and BTN_TL2 or ABS_HAT2Y (left/ZL). - If only one trigger-button combination is present (upper+lower), they are - reported as "right" triggers (BTN_TR/ABS_HAT1X). (ABS trigger values start at 0, pressure is reported as positive values) Menu-Pad: @@ -155,5 +156,9 @@ Menu-Pad: Rumble: Rumble is advertised as FF_RUMBLE. +Motion-tracking: + Motion-tracking is defined in ./Documentation/input/motion-tracking.txt and + gamepads shall comply to the rules defined there. + ---------------------------------------------------------------------------- Written 2013 by David Herrmann <dh.herrmann@gmail.com> diff --git a/Documentation/input/motion-tracking.txt b/Documentation/input/motion-tracking.txt new file mode 100644 index 0000000..d34a290 --- /dev/null +++ b/Documentation/input/motion-tracking.txt @@ -0,0 +1,176 @@ + Motion Tracking API +---------------------------------------------------------------------------- + +1. Intro +~~~~~~~~ +Motion tracking devices produce device motion events generated from an +accelerometer, gyroscope or compass. These data can be returned to user-space +via input events. This document defines how these data are reported. + +2. Devices +~~~~~~~~~~ +In this document, a "device" is one of: + - accelerometer + - gyroscope + - compass + +These devices returned their information via different APIs in the past. To +unify them and define a common API, a set of input evdev codes was created. Old +drivers might continue using their API, but developers are encouraged to use +the input evdev API for new drivers. + +2.1 Axes +~~~~~~~~ +Movement data is usually returned as absolute data for the 3 axes of a device. +In this context, the three axes are defined in a right-handed coordinate +system as: + - X: Axis goes from the left to the right side of the device + - Y: Axis goes from the bottom to the top of the device + - Z: Axis goes from the back to the front of the device + +The front of a device is the side faced to the user. For a mobile-phone it +would be the screen. For devices without a screen, the top is usually the +side with the most buttons on it. + + Example: Mobile-Phone + +-------------------------------------------------------------------------+ + | TOP | + | | + | | + | +---------------------------+ | + | |\ ________________________ \ .__ | + | \ \ \ \ \ |\ | + | \ \ \ __ \ \ \ RIGHT| + | \ \ \ /| \ \ \__ | + | \ \ \ __/ \ \ |\ | + | \ \ \ /| \ \ \ (Y Axis) | + | \ \ \ __/ (Z axis) \ \ \__ | + | \ \ \ /| \ \ |\ | + | LEFT \ \ \ / \ \ \ | + | \ \ \ FRONT \ \ \ | + | \ \ \ \ \ | + | \ \ \_______________________\ \ | + | \ \ ___ \ | + | /\ \ \__\ \ | + | __/ \ +---------------------------+ | + | /| \|___________________________| | + | / BACK | + | (X axis) | + | ------->------->------->-------> | + | | + | | + | BOTTOM | + +-------------------------------------------------------------------------+ + +Rotation-data is reported as counter-clockwise rotation on an axis when viewed +from the top of the axis, as given by the right hand rule. For a given axis, +the reported rotation would be: + ____ + //| + // | (axis) + // + // + . // __ + / // /\ + | // | + \ // / (counter-clockwise rotation) + *.___.* + // + // + +2.2 Calibration +~~~~~~~~~~~~~~~ +Motion sensors are often highly sensitive and need precise calibration. Users +are advised to perform neutral-point calibration themselves or to implement a +state-machine to normalize input data automatically. + +Kernel devices may perform their own calibration and/or normalization. However, +this is usually sparse and, if implemented, transparent to the user. + +There is currently no way to feed calibration data into the kernel in a generic +way. Proposals welcome! + +2.3 Units +~~~~~~~~~ +(NOTE: This section describes an experimental API. Currently, no device complies +to these rules so this might change in the future.) + +Reported data shall be returned as: + - Acceleration: 1/(input_absinfo.resolution) G + - Rotation: 1/(input_absinfo.resolution) degree per second + +Acceleration is reported in units of G as opposed to m/s^2, because acceleration +sensors internally work based on gravitation. Since the conversion to m/s^2 is +location dependent, applications should either approximate the conversion +factor as 9.8 m/s^2 or if more precision is desired obtain a scaling factor +by other means e.g. GPS. + +However, for most devices the reported units are unknown (more precisely: no +one has the time to measure them and figure them out). Therefore, user-space +shall use abs-minimum and abs-maximum to calculate relative data and use that +instead. Devices which return wrong units may be fixed in the future to comply +to these rules. + +2.4 Timestamps +~~~~~~~~~~~~~~ +For motion tracking purposes the time delta between consecutive motion events +is important for mathematical operations such as differentiation and integration. +The time delta could be derived from the 'time' field in 'struct input_event' by +subtracting the time between consecutive events. However, this timestamp may not +provide enough accuracy depending on the use case, since it is based upon time of +processing within the input layer versus time of arrival in the kernel or the +time the hardware sent the data. There is often a small variable time difference +between these. + +Optionally, hardware may provide a hardware timestamp produced at the time it +sampled the motion sensors. This timestamp is is exposed through +'MSC_TIMESTAMP' event, which provides timing information in microseconds. +If available, MSC_TIMESTAMP is the recommended approach for calculation of time +deltas. + +3.1 Accelerometer +~~~~~~~~~~~~~~~~~ +Accelerometers measure movement acceleration of devices. Any combination of the +three available axes can be used. Usually, all three are supported. + +Data is provided as absolute acceleration. A positive integer defines the +acceleration in the direction of an axis. A negative integer defines +acceleration in the opposite direction. + +The evdev ABS codes used are: + - ABS_ACCEL_X: X axis + - ABS_ACCEL_Y: Y axis + - ABS_ACCEL_Z: Z axis + +3.2 Gyroscope +~~~~~~~~~~~~~ +A gyroscope measures rotational speed (*not* acceleration!). Any combination of +the three available axes can be used. Usually, all three are supported. + +Data is provided as absolute speed. A positive integer defines the rotational +speed in counter-clockwise order around a given axis when viewed from the top of +the axis. A negative integer defines it in clockwise order. + +The evdev ABS codes used are: + - ABS_GYRO_X: X axis (also: Pitch) + - ABS_GYRO_Y: Y axis (also: Roll) + - ABS_GYRO_Z: Z axis (also: Azimuth/Yaw) + +3.3 Compass +~~~~~~~~~~~ +(NOTE: No compass device currently uses the evdev input subsystem. Thus, this +API is only a proposal, it hasn't been implemented, yet.) + +A compass measures the ambient magnetic field of the three defined axes. This +makes the data self-contained and independent of the current device position. +Any combination of the three axes can be used. Usually all three are supported, +otherwise, it's not really useful as a compass. + +Proposed evdev ABS codes are: + - ABS_COMPASS_X: X axis + - ABS_COMPASS_Y: Y axis + - ABS_COMPASS_Z: Z axis + +---------------------------------------------------------------------------- + (c) 2013 David Herrmann <dh.herrmann at gmail.com> + (c) 2016 Roderick Colenbrander <roderick.colenbrander@sony.com> diff --git a/include/uapi/linux/input-event-codes.h b/include/uapi/linux/input-event-codes.h index 7bf2a2e..0cacfe7 100644 --- a/include/uapi/linux/input-event-codes.h +++ b/include/uapi/linux/input-event-codes.h @@ -763,6 +763,13 @@ #define ABS_MAX 0x3f #define ABS_CNT (ABS_MAX+1) +#define ABS_GYRO_X 0x40 /* Gyroscope X axis */ +#define ABS_GYRO_Y 0x41 /* Gyroscope Y axis */ +#define ABS_GYRO_Z 0x42 /* Gyroscope Z axis */ +#define ABS_ACCEL_X 0x43 /* Accelerometer X axis */ +#define ABS_ACCEL_Y 0x44 /* Accelerometer Y axis */ +#define ABS_ACCEL_Z 0x45 /* Accelerometer Z axis */ + /* * Due to API restrictions the legacy evdev API only supports ABS values up to * ABS_MAX/CNT. Use the extended *ABS2 ioctls to operate on the full range of