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authorBoris Brezillon <boris.brezillon@free-electrons.com>2016-06-14 12:13:09 +0300
committerThierry Reding <thierry.reding@gmail.com>2016-07-08 18:52:18 +0300
commita6a0dbbcfa469cf3e5c4d9522106c0b7b9e9e373 (patch)
treece43ebafbd0d41bd485b7d5751a3b02aee914ef4 /include/linux/pwm.h
parent1a695a905c18548062509178b98bc91e67510864 (diff)
downloadlinux-a6a0dbbcfa469cf3e5c4d9522106c0b7b9e9e373.tar.xz
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>
Diffstat (limited to 'include/linux/pwm.h')
-rw-r--r--include/linux/pwm.h33
1 files changed, 33 insertions, 0 deletions
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
@@ -148,6 +148,39 @@ static inline void pwm_get_args(const struct pwm_device *pwm,
}
/**
+ * 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
* @free: optional hook for freeing a PWM