On 2021-06-08 12:32 a.m., Anand K Mistry wrote:

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 reasonable.

Signed-off-by: Anand K Mistry amistry@google.com

Thanks for your patch but this code has changed on amd-staging-drm-next.

Can you try with the latest? The new backlight_update_status will always return 0 now.

Harry

---

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) else 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)