| Message ID | 20190925150945.27706-1-helen.koike@collabora.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | media: vidioc-queryctrl.rst: clarify combining READ_ONLY with WRITE_ONLY | expand |
On 9/25/19 5:09 PM, Helen Koike wrote: > Make it clear in the documentation that V4L2_CTRL_FLAG_READ_ONLY doesn't > conflict with V4L2_CTRL_FLAG_WRITE_ONLY. Also make it clear that > if both are combined then the control has read and write permissions. That doesn't look right. This is the test in v4l2-compliance: __u32 rw_mask = V4L2_CTRL_FLAG_READ_ONLY | V4L2_CTRL_FLAG_WRITE_ONLY; if ((fl & rw_mask) == rw_mask) return fail("can't read nor write this control\n"); If both flags are set, then a fail is reported. Did you mis-read? Setting both flags makes no sense. Regards, Hans > > Signed-off-by: Helen Koike <helen.koike@collabora.com> > > --- > Hi, > > v4l2-compliance expects both flags for read and write permissions, so I > would like to make it clear in the docs. > Please let me know if this is not the case. > > Thanks > Helen > --- > Documentation/media/uapi/v4l/vidioc-queryctrl.rst | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/Documentation/media/uapi/v4l/vidioc-queryctrl.rst b/Documentation/media/uapi/v4l/vidioc-queryctrl.rst > index a3d56ffbf4cc..1d3aecdf679f 100644 > --- a/Documentation/media/uapi/v4l/vidioc-queryctrl.rst > +++ b/Documentation/media/uapi/v4l/vidioc-queryctrl.rst > @@ -500,6 +500,11 @@ See also the examples in :ref:`control`. > - 0x0004 > - This control is permanently readable only. Any attempt to change > the control will result in an ``EINVAL`` error code. > + > + .. note:: > + > + If combined with ``V4L2_CTRL_FLAG_WRITE_ONLY``, then both, read > + and write are allowed. > * - ``V4L2_CTRL_FLAG_UPDATE`` > - 0x0008 > - A hint that changing this control may affect the value of other > @@ -523,6 +528,11 @@ See also the examples in :ref:`control`. > where writing a value will cause the device to carry out a given > action (e. g. motor control) but no meaningful value can be > returned. > + > + .. note:: > + > + If combined with ``V4L2_CTRL_FLAG_READ_ONLY``, then both, read > + and write are allowed. > * - ``V4L2_CTRL_FLAG_VOLATILE`` > - 0x0080 > - This control is volatile, which means that the value of the >
Hi Hans On 9/25/19 12:17 PM, Hans Verkuil wrote: > On 9/25/19 5:09 PM, Helen Koike wrote: >> Make it clear in the documentation that V4L2_CTRL_FLAG_READ_ONLY doesn't >> conflict with V4L2_CTRL_FLAG_WRITE_ONLY. Also make it clear that >> if both are combined then the control has read and write permissions. > > That doesn't look right. > > This is the test in v4l2-compliance: > > __u32 rw_mask = V4L2_CTRL_FLAG_READ_ONLY | V4L2_CTRL_FLAG_WRITE_ONLY; > > if ((fl & rw_mask) == rw_mask) > return fail("can't read nor write this control\n"); > > If both flags are set, then a fail is reported. > > Did you mis-read? > > Setting both flags makes no sense. Maybe I misunderstood the V4L2_CTRL_TYPE_CTRL_CLASS, from v4l2-compliance: case V4L2_CTRL_TYPE_CTRL_CLASS: if (fl != (V4L2_CTRL_FLAG_READ_ONLY | V4L2_CTRL_FLAG_WRITE_ONLY)) return fail("invalid flags for control class\n"); I was confused why vivid was using both flags in vivid_ctrl_class (and also the debayer patch that was following this model). Why both flags are expected when this type is used? Thanks, Helen > > Regards, > > Hans > >> >> Signed-off-by: Helen Koike <helen.koike@collabora.com> >> >> --- >> Hi, >> >> v4l2-compliance expects both flags for read and write permissions, so I >> would like to make it clear in the docs. >> Please let me know if this is not the case. >> >> Thanks >> Helen >> --- >> Documentation/media/uapi/v4l/vidioc-queryctrl.rst | 10 ++++++++++ >> 1 file changed, 10 insertions(+) >> >> diff --git a/Documentation/media/uapi/v4l/vidioc-queryctrl.rst b/Documentation/media/uapi/v4l/vidioc-queryctrl.rst >> index a3d56ffbf4cc..1d3aecdf679f 100644 >> --- a/Documentation/media/uapi/v4l/vidioc-queryctrl.rst >> +++ b/Documentation/media/uapi/v4l/vidioc-queryctrl.rst >> @@ -500,6 +500,11 @@ See also the examples in :ref:`control`. >> - 0x0004 >> - This control is permanently readable only. Any attempt to change >> the control will result in an ``EINVAL`` error code. >> + >> + .. note:: >> + >> + If combined with ``V4L2_CTRL_FLAG_WRITE_ONLY``, then both, read >> + and write are allowed. >> * - ``V4L2_CTRL_FLAG_UPDATE`` >> - 0x0008 >> - A hint that changing this control may affect the value of other >> @@ -523,6 +528,11 @@ See also the examples in :ref:`control`. >> where writing a value will cause the device to carry out a given >> action (e. g. motor control) but no meaningful value can be >> returned. >> + >> + .. note:: >> + >> + If combined with ``V4L2_CTRL_FLAG_READ_ONLY``, then both, read >> + and write are allowed. >> * - ``V4L2_CTRL_FLAG_VOLATILE`` >> - 0x0080 >> - This control is volatile, which means that the value of the >> >
On 9/25/19 6:29 PM, Helen Koike wrote: > Hi Hans > > On 9/25/19 12:17 PM, Hans Verkuil wrote: >> On 9/25/19 5:09 PM, Helen Koike wrote: >>> Make it clear in the documentation that V4L2_CTRL_FLAG_READ_ONLY doesn't >>> conflict with V4L2_CTRL_FLAG_WRITE_ONLY. Also make it clear that >>> if both are combined then the control has read and write permissions. >> >> That doesn't look right. >> >> This is the test in v4l2-compliance: >> >> __u32 rw_mask = V4L2_CTRL_FLAG_READ_ONLY | V4L2_CTRL_FLAG_WRITE_ONLY; >> >> if ((fl & rw_mask) == rw_mask) >> return fail("can't read nor write this control\n"); >> >> If both flags are set, then a fail is reported. >> >> Did you mis-read? >> >> Setting both flags makes no sense. > > Maybe I misunderstood the V4L2_CTRL_TYPE_CTRL_CLASS, from v4l2-compliance: > > case V4L2_CTRL_TYPE_CTRL_CLASS: > if (fl != (V4L2_CTRL_FLAG_READ_ONLY | V4L2_CTRL_FLAG_WRITE_ONLY)) > return fail("invalid flags for control class\n"); > > I was confused why vivid was using both flags in vivid_ctrl_class (and also the debayer patch that was following this model). > > Why both flags are expected when this type is used? Ah, now I understand. This is specific to control classes: such controls cannot be read nor written. They just provide a name for the control class, but both G_CTRL and S_CTRL should fail. So this specific combination of flags is specific to control classes only. This works because a 'get' will fail if WRITE_ONLY is set, and a 'set' will fail if READ_ONLY is set. Setting both flags will cause both 'get' and 'set' to fail. It is admittedly a bit confusing. Regards, Hans > > Thanks, > Helen > >> >> Regards, >> >> Hans >> >>> >>> Signed-off-by: Helen Koike <helen.koike@collabora.com> >>> >>> --- >>> Hi, >>> >>> v4l2-compliance expects both flags for read and write permissions, so I >>> would like to make it clear in the docs. >>> Please let me know if this is not the case. >>> >>> Thanks >>> Helen >>> --- >>> Documentation/media/uapi/v4l/vidioc-queryctrl.rst | 10 ++++++++++ >>> 1 file changed, 10 insertions(+) >>> >>> diff --git a/Documentation/media/uapi/v4l/vidioc-queryctrl.rst b/Documentation/media/uapi/v4l/vidioc-queryctrl.rst >>> index a3d56ffbf4cc..1d3aecdf679f 100644 >>> --- a/Documentation/media/uapi/v4l/vidioc-queryctrl.rst >>> +++ b/Documentation/media/uapi/v4l/vidioc-queryctrl.rst >>> @@ -500,6 +500,11 @@ See also the examples in :ref:`control`. >>> - 0x0004 >>> - This control is permanently readable only. Any attempt to change >>> the control will result in an ``EINVAL`` error code. >>> + >>> + .. note:: >>> + >>> + If combined with ``V4L2_CTRL_FLAG_WRITE_ONLY``, then both, read >>> + and write are allowed. >>> * - ``V4L2_CTRL_FLAG_UPDATE`` >>> - 0x0008 >>> - A hint that changing this control may affect the value of other >>> @@ -523,6 +528,11 @@ See also the examples in :ref:`control`. >>> where writing a value will cause the device to carry out a given >>> action (e. g. motor control) but no meaningful value can be >>> returned. >>> + >>> + .. note:: >>> + >>> + If combined with ``V4L2_CTRL_FLAG_READ_ONLY``, then both, read >>> + and write are allowed. >>> * - ``V4L2_CTRL_FLAG_VOLATILE`` >>> - 0x0080 >>> - This control is volatile, which means that the value of the >>> >>
diff --git a/Documentation/media/uapi/v4l/vidioc-queryctrl.rst b/Documentation/media/uapi/v4l/vidioc-queryctrl.rst index a3d56ffbf4cc..1d3aecdf679f 100644 --- a/Documentation/media/uapi/v4l/vidioc-queryctrl.rst +++ b/Documentation/media/uapi/v4l/vidioc-queryctrl.rst @@ -500,6 +500,11 @@ See also the examples in :ref:`control`. - 0x0004 - This control is permanently readable only. Any attempt to change the control will result in an ``EINVAL`` error code. + + .. note:: + + If combined with ``V4L2_CTRL_FLAG_WRITE_ONLY``, then both, read + and write are allowed. * - ``V4L2_CTRL_FLAG_UPDATE`` - 0x0008 - A hint that changing this control may affect the value of other @@ -523,6 +528,11 @@ See also the examples in :ref:`control`. where writing a value will cause the device to carry out a given action (e. g. motor control) but no meaningful value can be returned. + + .. note:: + + If combined with ``V4L2_CTRL_FLAG_READ_ONLY``, then both, read + and write are allowed. * - ``V4L2_CTRL_FLAG_VOLATILE`` - 0x0080 - This control is volatile, which means that the value of the
Make it clear in the documentation that V4L2_CTRL_FLAG_READ_ONLY doesn't conflict with V4L2_CTRL_FLAG_WRITE_ONLY. Also make it clear that if both are combined then the control has read and write permissions. Signed-off-by: Helen Koike <helen.koike@collabora.com> --- Hi, v4l2-compliance expects both flags for read and write permissions, so I would like to make it clear in the docs. Please let me know if this is not the case. Thanks Helen --- Documentation/media/uapi/v4l/vidioc-queryctrl.rst | 10 ++++++++++ 1 file changed, 10 insertions(+)