From a6a0dbbcfa469cf3e5c4d9522106c0b7b9e9e373 Mon Sep 17 00:00:00 2001 From: Boris Brezillon Date: Tue, 14 Jun 2016 11:13:09 +0200 Subject: [PATCH] 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 Tested-by: Heiko Stuebner Signed-off-by: Thierry Reding --- include/linux/pwm.h | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) diff --git a/include/linux/pwm.h b/include/linux/pwm.h index 17018f3c066e..a100f6e80738 100644 --- a/include/linux/pwm.h +++ b/include/linux/pwm.h @@ -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 -- 2.34.1