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

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Date:   Tue,  8 Jun 2021 14:32:38 +1000
From:   Anand K Mistry <amistry@...gle.com>
To:     amd-gfx@...ts.freedesktop.org
Cc:     Anand K Mistry <amistry@...gle.com>,
        Alex Deucher <alexander.deucher@....com>,
        Aurabindo Pillai <aurabindo.pillai@....com>,
        Bas Nieuwenhuizen <bas@...nieuwenhuizen.nl>,
        "Christian König" <christian.koenig@....com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>, Eryk Brol <eryk.brol@....com>,
        Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Nicholas Kazlauskas <nicholas.kazlauskas@....com>,
        Nikola Cornij <nikola.cornij@....com>,
        Qingqing Zhuo <qingqing.zhuo@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Wayne Lin <Wayne.Lin@....com>, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] drm/amd/display: Fix error code on failure to set brightness

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@...gle.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)
 	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)
-- 
2.32.0.rc1.229.g3e70b5a671-goog