[v2] Input: document inhibiting
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Message ID 20200617101822.8558-1-andrzej.p@collabora.com
State Not Applicable, archived
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  • [v2] Input: document inhibiting
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Andrzej Pietrasiewicz June 17, 2020, 10:18 a.m. UTC
Document inhibiting input devices and its relation to being
a wakeup source.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
---
v1..v2:

- Addressed editorial comments from Randy
- Added a paragraph by Hans

 Documentation/input/input-programming.rst | 40 +++++++++++++++++++++++
 1 file changed, 40 insertions(+)

Comments

Hans de Goede June 17, 2020, 10:21 a.m. UTC | #1
Hi,

On 6/17/20 12:18 PM, Andrzej Pietrasiewicz wrote:
> Document inhibiting input devices and its relation to being
> a wakeup source.
> 
> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> ---
> v1..v2:
> 
> - Addressed editorial comments from Randy
> - Added a paragraph by Hans

Thank you.

v2 looks good to me:

Reviewed-by: Hans de Goede <hdegoede@redhat.com>

Regards,

Hans



> 
>   Documentation/input/input-programming.rst | 40 +++++++++++++++++++++++
>   1 file changed, 40 insertions(+)
> 
> diff --git a/Documentation/input/input-programming.rst b/Documentation/input/input-programming.rst
> index 45a4c6e05e39..7432315cc829 100644
> --- a/Documentation/input/input-programming.rst
> +++ b/Documentation/input/input-programming.rst
> @@ -164,6 +164,46 @@ disconnects. Calls to both callbacks are serialized.
>   The open() callback should return a 0 in case of success or any nonzero value
>   in case of failure. The close() callback (which is void) must always succeed.
>   
> +Inhibiting input devices
> +~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +Inhibiting a device means ignoring input events from it. As such it is about maintaining
> +relationships with input handlers - either already existing relationships, or relationships
> +to be established while the device is in inhibited state.
> +
> +If a device is inhibited, no input handler will receive events from it.
> +
> +The fact that nobody wants events from the device is exploited further, by calling device's
> +close() (if there are users) and open() (if there are users) on inhibit and uninhibit
> +operations, respectively. Indeed, the meaning of close() is to stop providing events
> +to the input core and that of open() is to start providing events to the input core.
> +
> +Calling the device's close() method on inhibit (if there are users) allows the driver
> +to save power. Either by directly powering down the device or by releasing the
> +runtime-pm reference it got in open() when the driver is using runtime-pm.
> +
> +Inhibiting and uninhibiting are orthogonal to opening and closing the device by input
> +handlers. Userspace might want to inhibit a device in anticipation before any handler is
> +positively matched against it.
> +
> +Inhibiting and uninhibiting are orthogonal to device's being a wakeup source, too. Being a
> +wakeup source plays a role when the system is sleeping, not when the system is operating.
> +How drivers should program their interaction between inhibiting, sleeping and being a wakeup
> +source is driver-specific.
> +
> +Taking the analogy with the network devices - bringing a network interface down doesn't mean
> +that it should be impossible be wake the system up on LAN through this interface. So, there
> +may be input drivers which should be considered wakeup sources even when inhibited. Actually,
> +in many I2C input devices their interrupt is declared a wakeup interrupt and its handling
> +happens in driver's core, which is not aware of input-specific inhibit (nor should it be).
> +Composite devices containing several interfaces can be inhibited on a per-interface basis and
> +e.g. inhibiting one interface shouldn't affect the device's capability of being a wakeup source.
> +
> +If a device is to be considered a wakeup source while inhibited, special care must be taken when
> +programming its suspend(), as it might need to call device's open(). Depending on what close()
> +means for the device in question, not opening() it before going to sleep might make it
> +impossible to provide any wakeup events. The device is going to sleep anyway.
> +
>   Basic event types
>   ~~~~~~~~~~~~~~~~~
>   
>
Randy Dunlap June 17, 2020, 4:52 p.m. UTC | #2
On 6/17/20 3:18 AM, Andrzej Pietrasiewicz wrote:
> Document inhibiting input devices and its relation to being
> a wakeup source.
> 
> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> ---
> v1..v2:
> 
> - Addressed editorial comments from Randy
> - Added a paragraph by Hans
> 
>  Documentation/input/input-programming.rst | 40 +++++++++++++++++++++++
>  1 file changed, 40 insertions(+)
> 
> diff --git a/Documentation/input/input-programming.rst b/Documentation/input/input-programming.rst
> index 45a4c6e05e39..7432315cc829 100644
> --- a/Documentation/input/input-programming.rst
> +++ b/Documentation/input/input-programming.rst
> @@ -164,6 +164,46 @@ disconnects. Calls to both callbacks are serialized.
>  The open() callback should return a 0 in case of success or any nonzero value
>  in case of failure. The close() callback (which is void) must always succeed.
>  
> +Inhibiting input devices
> +~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +Inhibiting a device means ignoring input events from it. As such it is about maintaining
> +relationships with input handlers - either already existing relationships, or relationships
> +to be established while the device is in inhibited state.
> +
> +If a device is inhibited, no input handler will receive events from it.
> +
> +The fact that nobody wants events from the device is exploited further, by calling device's
> +close() (if there are users) and open() (if there are users) on inhibit and uninhibit
> +operations, respectively. Indeed, the meaning of close() is to stop providing events
> +to the input core and that of open() is to start providing events to the input core.
> +
> +Calling the device's close() method on inhibit (if there are users) allows the driver
> +to save power. Either by directly powering down the device or by releasing the
> +runtime-pm reference it got in open() when the driver is using runtime-pm.
> +
> +Inhibiting and uninhibiting are orthogonal to opening and closing the device by input
> +handlers. Userspace might want to inhibit a device in anticipation before any handler is
> +positively matched against it.
> +
> +Inhibiting and uninhibiting are orthogonal to device's being a wakeup source, too. Being a
> +wakeup source plays a role when the system is sleeping, not when the system is operating.
> +How drivers should program their interaction between inhibiting, sleeping and being a wakeup
> +source is driver-specific.
> +
> +Taking the analogy with the network devices - bringing a network interface down doesn't mean
> +that it should be impossible be wake the system up on LAN through this interface. So, there
> +may be input drivers which should be considered wakeup sources even when inhibited. Actually,
> +in many I2C input devices their interrupt is declared a wakeup interrupt and its handling
> +happens in driver's core, which is not aware of input-specific inhibit (nor should it be).
> +Composite devices containing several interfaces can be inhibited on a per-interface basis and
> +e.g. inhibiting one interface shouldn't affect the device's capability of being a wakeup source.
> +
> +If a device is to be considered a wakeup source while inhibited, special care must be taken when
> +programming its suspend(), as it might need to call device's open(). Depending on what close()
> +means for the device in question, not opening() it before going to sleep might make it
> +impossible to provide any wakeup events. The device is going to sleep anyway.
> +
>  Basic event types
>  ~~~~~~~~~~~~~~~~~
>  
> 

Reviewed-by: Randy Dunlap <rdunlap@infradead.org>

Thanks.
Pavel Machek June 23, 2020, 1:35 p.m. UTC | #3
Hi!

> +Inhibiting input devices
> +~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +Inhibiting a device means ignoring input events from it. As such it is about maintaining
> +relationships with input handlers - either already existing relationships, or relationships
> +to be established while the device is in inhibited state.
> +
> +If a device is inhibited, no input handler will receive events from it.
> +
> +The fact that nobody wants events from the device is exploited further, by calling device's
> +close() (if there are users) and open() (if there are users) on inhibit and uninhibit
> +operations, respectively. Indeed, the meaning of close() is to stop providing events
> +to the input core and that of open() is to start providing events to the input core.
> +
> +Calling the device's close() method on inhibit (if there are users) allows the driver
> +to save power. Either by directly powering down the device or by releasing the
> +runtime-pm reference it got in open() when the driver is using runtime-pm.
> +
> +Inhibiting and uninhibiting are orthogonal to opening and closing the device by input
> +handlers. Userspace might want to inhibit a device in anticipation before any handler is
> +positively matched against it.

Ok.

> +Inhibiting and uninhibiting are orthogonal to device's being a wakeup source, too. 
> Being a +wakeup source plays a role when the system is sleeping, not when the system is 
> operating. +How drivers should program their interaction between inhibiting, sleeping 
> and being a wakeup +source is driver-specific. + +Taking the analogy with the network 

I don't believe making interaction driver-specific is good idea. We should decide
what reasonable behaviour is and then make drivers implement that...

Best regards,
									Pavel

Patch
diff mbox series

diff --git a/Documentation/input/input-programming.rst b/Documentation/input/input-programming.rst
index 45a4c6e05e39..7432315cc829 100644
--- a/Documentation/input/input-programming.rst
+++ b/Documentation/input/input-programming.rst
@@ -164,6 +164,46 @@  disconnects. Calls to both callbacks are serialized.
 The open() callback should return a 0 in case of success or any nonzero value
 in case of failure. The close() callback (which is void) must always succeed.
 
+Inhibiting input devices
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+Inhibiting a device means ignoring input events from it. As such it is about maintaining
+relationships with input handlers - either already existing relationships, or relationships
+to be established while the device is in inhibited state.
+
+If a device is inhibited, no input handler will receive events from it.
+
+The fact that nobody wants events from the device is exploited further, by calling device's
+close() (if there are users) and open() (if there are users) on inhibit and uninhibit
+operations, respectively. Indeed, the meaning of close() is to stop providing events
+to the input core and that of open() is to start providing events to the input core.
+
+Calling the device's close() method on inhibit (if there are users) allows the driver
+to save power. Either by directly powering down the device or by releasing the
+runtime-pm reference it got in open() when the driver is using runtime-pm.
+
+Inhibiting and uninhibiting are orthogonal to opening and closing the device by input
+handlers. Userspace might want to inhibit a device in anticipation before any handler is
+positively matched against it.
+
+Inhibiting and uninhibiting are orthogonal to device's being a wakeup source, too. Being a
+wakeup source plays a role when the system is sleeping, not when the system is operating.
+How drivers should program their interaction between inhibiting, sleeping and being a wakeup
+source is driver-specific.
+
+Taking the analogy with the network devices - bringing a network interface down doesn't mean
+that it should be impossible be wake the system up on LAN through this interface. So, there
+may be input drivers which should be considered wakeup sources even when inhibited. Actually,
+in many I2C input devices their interrupt is declared a wakeup interrupt and its handling
+happens in driver's core, which is not aware of input-specific inhibit (nor should it be).
+Composite devices containing several interfaces can be inhibited on a per-interface basis and
+e.g. inhibiting one interface shouldn't affect the device's capability of being a wakeup source.
+
+If a device is to be considered a wakeup source while inhibited, special care must be taken when
+programming its suspend(), as it might need to call device's open(). Depending on what close()
+means for the device in question, not opening() it before going to sleep might make it
+impossible to provide any wakeup events. The device is going to sleep anyway.
+
 Basic event types
 ~~~~~~~~~~~~~~~~~