[PATCH] drm/amd/display: Fix error code on failure to set brightness

Anand K Mistry amistry at google.com
Tue Jun 8 04:32:38 UTC 2021

The backlight_ops.update_status function is required to return a
negative error code on failure. Returning a positive code may be
interpreted as a success. This is true for the 'brightness' sysfs file,
which passes through a non-zero value as the return value of the write()
syscall. This is interpreted in user-space as a successful write of 1
character, which is obviously wrong.

It's not clear exactly what error code to use, but EINVAL should be

Signed-off-by: Anand K Mistry <amistry at google.com>

 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 652cc1a0e450..ad322613390d 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -3431,7 +3431,7 @@ static int amdgpu_dm_backlight_update_status(struct backlight_device *bd)
 		rc = dc_link_set_backlight_level(dm->backlight_link, brightness, 0);
-	return rc ? 0 : 1;
+	return rc ? 0 : -EINVAL;
 static int amdgpu_dm_backlight_get_brightness(struct backlight_device *bd)

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