pwm: Add PWM capture support

Supply a PWM capture callback op in order to pass back information
obtained by running analysis on a PWM signal. This would normally (at
least during testing) be called from the sysfs routines with a view to
printing out PWM capture data which has been encoded into a string.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
[thierry.reding@gmail.com: make capture data unsigned int for symmetry]
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/core.c

@@ -524,6 +524,33 @@ int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state)
 }
 EXPORT_SYMBOL_GPL(pwm_apply_state);
 
+/**
+ * pwm_capture() - capture and report a PWM signal
+ * @pwm: PWM device
+ * @result: structure to fill with capture result
+ * @timeout: time to wait, in milliseconds, before giving up on capture
+ *
+ * Returns: 0 on success or a negative error code on failure.
+ */
+int pwm_capture(struct pwm_device *pwm, struct pwm_capture *result,
+		unsigned long timeout)
+{
+	int err;
+
+	if (!pwm || !pwm->chip->ops)
+		return -EINVAL;
+
+	if (!pwm->chip->ops->capture)
+		return -ENOSYS;
+
+	mutex_lock(&pwm_lock);
+	err = pwm->chip->ops->capture(pwm->chip, pwm, result, timeout);
+	mutex_unlock(&pwm_lock);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(pwm_capture);
+
 /**
  * pwm_adjust_config() - adjust the current PWM config to the PWM arguments
  * @pwm: PWM device