leds: allow led-drivers to use a variable range of brightness values

This patch allows drivers to override the default maximum brightness value
of 255.  We take care to preserve backwards-compatibility as much as
possible, so that user-space ABI doesn't change for existing drivers.
LED trigger code has also been updated to use the per-LED maximum.

Signed-off-by: Guennadi Liakhovetski <lg@denx.de>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

1 files changed, 20 insertions, 1 deletions

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 52f82e3ea13a..f2cc13d76810 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -64,7 +64,16 @@ static ssize_t led_brightness_store(struct device *dev,
         return ret;
 }
 
+static ssize_t led_max_brightness_show(struct device *dev,
+                struct device_attribute *attr, char *buf)
+{
+        struct led_classdev *led_cdev = dev_get_drvdata(dev);
+
+        return sprintf(buf, "%u\n", led_cdev->max_brightness);
+}
+
 static DEVICE_ATTR(brightness, 0644, led_brightness_show, led_brightness_store);
+static DEVICE_ATTR(max_brightness, 0444, led_max_brightness_show, NULL);
 #ifdef CONFIG_LEDS_TRIGGERS
 static DEVICE_ATTR(trigger, 0644, led_trigger_show, led_trigger_store);
 #endif
@@ -138,6 +147,13 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev)
         list_add_tail(&led_cdev->node, &leds_list);
         up_write(&leds_list_lock);
 
+        if (!led_cdev->max_brightness)
+                led_cdev->max_brightness = LED_FULL;
+
+        rc = device_create_file(led_cdev->dev, &dev_attr_max_brightness);
+        if (rc)
+                goto err_out_attr_max;
+
         led_update_brightness(led_cdev);
 
 #ifdef CONFIG_LEDS_TRIGGERS
@@ -155,9 +171,11 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev)
 
 #ifdef CONFIG_LEDS_TRIGGERS
 err_out_led_list:
+        device_remove_file(led_cdev->dev, &dev_attr_max_brightness);
+#endif
+err_out_attr_max:
         device_remove_file(led_cdev->dev, &dev_attr_brightness);
         list_del(&led_cdev->node);
-#endif
 err_out:
         device_unregister(led_cdev->dev);
         return rc;
@@ -172,6 +190,7 @@ EXPORT_SYMBOL_GPL(led_classdev_register);
  */
 void led_classdev_unregister(struct led_classdev *led_cdev)
 {
+        device_remove_file(led_cdev->dev, &dev_attr_max_brightness);
         device_remove_file(led_cdev->dev, &dev_attr_brightness);
 #ifdef CONFIG_LEDS_TRIGGERS
         device_remove_file(led_cdev->dev, &dev_attr_trigger);