leds: core: avoid error message when a USB LED device is unplugged

When a USB LED device is unplugged the remove call chain calls led_classdev_unregister which tries to switch the LED off. As the device has been removed already this results in a ENODEV error message in dmesg.
Avoid this error message by ignoring ENODEV in calls from led_classdev_unregister if the LED device is flagged as pluggable.

Therefore a new flag LED_HW_PLUGGABLE was introduced which should be set by all LED drivers handling pluggable LED devices (mainly USB LED devices).

Signed-off-by Heiner Kallweit <[email protected]>

---
  drivers/leds/led-class.c | 2 ++
  drivers/leds/led-core.c  | 5 ++++-
  include/linux/leds.h     | 2 ++
  3 files changed, 8 insertions(+), 1 deletion(-)

drivers/leds/led-class.c +2 -0

index 14139c3..aa84e5b 100644
@@ -245,6 +245,8 @@ void led_classdev_unregister(struct led_classdev *led_cdev)
  	up_write(&led_cdev->trigger_lock);
  #endif
 
+	led_cdev->flags |= LED_UNREGISTERING;
+
  	/* Stop blinking */
  	led_stop_software_blink(led_cdev);
 

drivers/leds/led-core.c +4 -1

index 19e1e60..ad684b6 100644
@@ -98,7 +98,10 @@ static void set_brightness_delayed(struct work_struct *ws)
  						led_cdev->delayed_set_value);
  	else
  		ret = -ENOTSUPP;
-	if (ret < 0)
+	if (ret < 0 &&
+	    /* LED HW might have been unplugged, therefore don't warn */
+	    !(ret == -ENODEV && (led_cdev->flags & LED_UNREGISTERING) &&
+	    (led_cdev->flags & LED_HW_PLUGGABLE)))
  		dev_err(led_cdev->dev,
  			"Setting an LED's brightness failed (%d)\n", ret);
  }

include/linux/leds.h +2 -0

index 4429887..24413a8 100644
@@ -39,6 +39,7 @@ struct led_classdev {
 
  	/* Lower 16 bits reflect status */
  #define LED_SUSPENDED		(1 << 0)
+#define LED_UNREGISTERING	(1 << 1)
  	/* Upper 16 bits reflect control information */
  #define LED_CORE_SUSPENDRESUME	(1 << 16)
  #define LED_BLINK_ONESHOT	(1 << 17)

@@ -48,6 +49,7 @@ struct led_classdev {
  #define LED_BLINK_DISABLE	(1 << 21)
  #define LED_SYSFS_DISABLE	(1 << 22)
  #define LED_DEV_CAP_FLASH	(1 << 23)
+#define LED_HW_PLUGGABLE	(1 << 24)
 
  	/* Set LED brightness level */
  	/* Must not sleep. If no non-blocking version can be provided

Hi Heiner,

Could you rebase this patch on the top of devel branch of LED git, please?

I am getting an error while applying it:

error: short SHA1 19e1e60 is ambiguous.
fatal: sha1 information is lacking or useless (drivers/leds/led-core.c). Repository lacks necessary blobs to fall back on 3-way merge.

It may have happened that you had some patches that are not in mainline kernel in the repository you produced the patch from. It is also possible that this is an issue with the git version I am using, so this would clarify the situation.

Thanks in advance.

Best Regards,
Jacek Anaszewski

Quoted 67 lines · Heiner Kallweit

When a USB LED device is unplugged the remove call chain calls led_classdev_unregister which tries to switch the LED off. As the device has been removed already this results in a ENODEV error message in dmesg.
Avoid this error message by ignoring ENODEV in calls from led_classdev_unregister if the LED device is flagged as pluggable.

Therefore a new flag LED_HW_PLUGGABLE was introduced which should be set by all LED drivers handling pluggable LED devices (mainly USB LED devices).

Signed-off-by Heiner Kallweit <[email protected]>

---
  drivers/leds/led-class.c | 2 ++
  drivers/leds/led-core.c  | 5 ++++-
  include/linux/leds.h     | 2 ++
  3 files changed, 8 insertions(+), 1 deletion(-)

drivers/leds/led-class.c +2 -0

index 14139c3..aa84e5b 100644
@@ -245,6 +245,8 @@ void led_classdev_unregister(struct led_classdev *led_cdev)
      up_write(&led_cdev->trigger_lock);
  #endif
 
+    led_cdev->flags |= LED_UNREGISTERING;
+
      /* Stop blinking */
      led_stop_software_blink(led_cdev);
 

drivers/leds/led-core.c +4 -1

index 19e1e60..ad684b6 100644
@@ -98,7 +98,10 @@ static void set_brightness_delayed(struct work_struct *ws)
                          led_cdev->delayed_set_value);
      else
          ret = -ENOTSUPP;
-    if (ret < 0)
+    if (ret < 0 &&
+        /* LED HW might have been unplugged, therefore don't warn */
+        !(ret == -ENODEV && (led_cdev->flags & LED_UNREGISTERING) &&
+        (led_cdev->flags & LED_HW_PLUGGABLE)))
          dev_err(led_cdev->dev,
              "Setting an LED's brightness failed (%d)\n", ret);
  }

include/linux/leds.h +2 -0

index 4429887..24413a8 100644
@@ -39,6 +39,7 @@ struct led_classdev {
 
      /* Lower 16 bits reflect status */
  #define LED_SUSPENDED        (1 << 0)
+#define LED_UNREGISTERING    (1 << 1)
      /* Upper 16 bits reflect control information */
  #define LED_CORE_SUSPENDRESUME    (1 << 16)
  #define LED_BLINK_ONESHOT    (1 << 17)

@@ -48,6 +49,7 @@ struct led_classdev {
  #define LED_BLINK_DISABLE    (1 << 21)
  #define LED_SYSFS_DISABLE    (1 << 22)
  #define LED_DEV_CAP_FLASH    (1 << 23)
+#define LED_HW_PLUGGABLE    (1 << 24)
 
      /* Set LED brightness level */
      /* Must not sleep. If no non-blocking version can be provided

Am 22.01.2016 um 09:45 schrieb Jacek Anaszewski:

Quoted 11 lines

Hi Heiner,

Could you rebase this patch on the top of devel branch of LED git, please?

I am getting an error while applying it:

error: short SHA1 19e1e60 is ambiguous.
fatal: sha1 information is lacking or useless (drivers/leds/led-core.c). Repository lacks necessary blobs to fall back on 3-way merge.

Quoted 5 lines

It may have happened that you had some patches that are not in mainline kernel in the repository you produced the patch from. It is also possible that this is an issue with the git version I am using, so this would clarify the situation.

Reason is the changed comment as it affects the context of this patch. Will rebase it and resend.