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pwm: Add a helper to prepare a new PWM state 

The pwm_init_state() helper prepares a new state object containing the
current PWM state except for the polarity and period fields which are
set to the reference values (those in struct pwm_args).

This is particularly useful for PWM users who want to apply a new duty-
cycle expressed relatively to the reference period without changing the
enable state.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
Boris Brezillon 2016-06-14 11:13:09 +02:00 committed by Thierry Reding
parent 1a695a905c
commit a6a0dbbcfa
1 changed files with 33 additions and 0 deletions
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33
include/linux/pwm.h
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@ -147,6 +147,39 @@ static inline void pwm_get_args(const struct pwm_device *pwm,
*args = pwm->args;
}
/**
* pwm_init_state() - prepare a new state to be applied with pwm_apply_state()
* @pwm: PWM device
* @state: state to fill with the prepared PWM state
*
* This functions prepares a state that can later be tweaked and applied
* to the PWM device with pwm_apply_state(). This is a convenient function
* that first retrieves the current PWM state and the replaces the period
* and polarity fields with the reference values defined in pwm->args.
* Once the function returns, you can adjust the ->enabled and ->duty_cycle
* fields according to your needs before calling pwm_apply_state().
*
* ->duty_cycle is initially set to zero to avoid cases where the current
* ->duty_cycle value exceed the pwm_args->period one, which would trigger
* an error if the user calls pwm_apply_state() without adjusting ->duty_cycle
* first.
*/
static inline void pwm_init_state(const struct pwm_device *pwm,
struct pwm_state *state)
{
struct pwm_args args;
/* First get the current state. */
pwm_get_state(pwm, state);
/* Then fill it with the reference config */
pwm_get_args(pwm, &args);
state->period = args.period;
state->polarity = args.polarity;
state->duty_cycle = 0;
}
/**
* struct pwm_ops - PWM controller operations
* @request: optional hook for requesting a PWM