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pwm: Clarify which state pwm_get_state() returns

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Given that lowlevel drivers usually cannot implement exactly what a
consumer requests with pwm_apply_state() there is some rounding
involved.

pwm_get_state() returns the setting that was requested most recently by
the consumer (opposed to what was actually implemented in hardware in
reply to the last request). Clarify this in the function kerneldoc.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
Uwe Kleine-König 2021-04-06 09:30:36 +02:00 committed by Thierry Reding
parent 9666cec380
commit 1a7a6e8072
2 changed files with 10 additions and 1 deletions
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6
Documentation/driver-api/pwm.rst
View File

@ -55,7 +55,11 @@ several parameter at once. For example, if you see pwm_config() and
pwm_{enable,disable}() calls in the same function, this probably means you
should switch to pwm_apply_state().
The PWM user API also allows one to query the PWM state with pwm_get_state().
The PWM user API also allows one to query the last applied PWM state with
pwm_get_last_applied_state(). Note this is different to what the driver has
actually implemented if the request cannot be implemented exactly with the
hardware in use. There is currently no way for consumers to get the actually
implemented settings.
In addition to the PWM state, the PWM API also exposes PWM arguments, which
are the reference PWM config one should use on this PWM.

5
include/linux/pwm.h
View File

@ -91,6 +91,11 @@ struct pwm_device {
* pwm_get_state() - retrieve the current PWM state
* @pwm: PWM device
* @state: state to fill with the current PWM state
*
* The returned PWM state represents the state that was applied by a previous call to
* pwm_apply_state(). Drivers may have to slightly tweak that state before programming it to
* hardware. If pwm_apply_state() was never called, this returns either the current hardware
* state (if supported) or the default settings.
*/
static inline void pwm_get_state(const struct pwm_device *pwm,
struct pwm_state *state)