pwm: Provide wrappers for storing and getting driver private data

These functions are useful to store and query driver private data
depending on the pwm_chip. After struct pwm_chip got its own struct
device, this can make use of dev_get_drvdata() and dev_set_drvdata() on
that device. These functions are required already now to convert
drivers to pwmchip_alloc() which must happen before changing
pwm_chip::dev.
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/67514cdf29d29bd8b4ad8d44fac87f6ae6dca1e5.1707900770.git.u.kleine-koenig@pengutronix.deSigned-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

include/linux/pwm.h

@@ -272,6 +272,7 @@ struct pwm_ops {
  * @npwm: number of PWMs controlled by this chip
  * @of_xlate: request a PWM device given a device tree PWM specifier
  * @atomic: can the driver's ->apply() be called in atomic context
+ * @driver_data: Private pointer for driver specific info
  * @pwms: array of PWM devices allocated by the framework
  */
 struct pwm_chip {
@@ -286,6 +287,7 @@ struct pwm_chip {
 	bool atomic;
 
 	/* only used internally by the PWM framework */
+	void *driver_data;
 	struct pwm_device *pwms;
 };
 
@@ -294,6 +296,24 @@ static inline struct device *pwmchip_parent(const struct pwm_chip *chip)
 	return chip->dev;
 }
 
+static inline void *pwmchip_get_drvdata(struct pwm_chip *chip)
+{
+	/*
+	 * After pwm_chip got a dedicated struct device, this can be replaced by
+	 * dev_get_drvdata(&chip->dev);
+	 */
+	return chip->driver_data;
+}
+
+static inline void pwmchip_set_drvdata(struct pwm_chip *chip, void *data)
+{
+	/*
+	 * After pwm_chip got a dedicated struct device, this can be replaced by
+	 * dev_set_drvdata(&chip->dev, data);
+	 */
+	chip->driver_data = data;
+}
+
 #if IS_ENABLED(CONFIG_PWM)
 /* PWM user APIs */
 int pwm_apply_might_sleep(struct pwm_device *pwm, const struct pwm_state *state);