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 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@xxxxxxxxxxxxxxxxxx>
Tested-by: Heiko Stuebner <heiko@xxxxxxxxx>
---
include/linux/pwm.h | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 17018f3..a100f6e 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
--
2.7.4
--
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