[PATCH 5.19 021/155] drm/i915/display: avoid warnings when registering dual panel backlight

Greg Kroah-Hartman
2022-09-06T14:02:37Z

From: Arun R Murthy <arun.r.murthy@intel.com>

[ Upstream commit 868e8e5156a1f8d92ca83fdbac6fd52798650792 ]

Commit 20f85ef89d94 ("drm/i915/backlight: use unique backlight device
names") added support for multiple backlight devices on dual panel
systems, but did so with error handling on -EEXIST from
backlight_device_register(). Unfortunately, that triggered a warning in
dmesg all the way down from sysfs_add_file_mode_ns() and
sysfs_warn_dup().

Instead of optimistically always attempting to register with the default
name ("intel_backlight", which we have to retain for backward
compatibility), check if a backlight device with the name exists first,
and, if so, use the card and connector based name.

v2: reworked on top of the patch commit 20f85ef89d94
("drm/i915/backlight: use unique backlight device names")
v3: fixed the ref count leak(Jani N)

Fixes: 20f85ef89d94 ("drm/i915/backlight: use unique backlight device names")
Signed-off-by: Arun R Murthy <arun.r.murthy@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220808035750.3111046-1-arun.r.murthy@intel.com
(cherry picked from commit 4234ea30051200fc6016de10e4d58369e60b38f1)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
.../gpu/drm/i915/display/intel_backlight.c | 26 +++++++++----------
1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_backlight.c b/drivers/gpu/drm/i915/display/intel_backlight.c
index c8e1fc53a881f..79f8a586623dc 100644
--- a/drivers/gpu/drm/i915/display/intel_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_backlight.c
@@ -970,26 +970,24 @@ int intel_backlight_device_register(struct intel_connector *connector)
if (!name)
return -ENOMEM;

- bd = backlight_device_register(name, connector->base.kdev, connector,
- &intel_backlight_device_ops, &props);
-
- /*
- * Using the same name independent of the drm device or connector
- * prevents registration of multiple backlight devices in the
- * driver. However, we need to use the default name for backward
- * compatibility. Use unique names for subsequent backlight devices as a
- * fallback when the default name already exists.
- */
- if (IS_ERR(bd) && PTR_ERR(bd) == -EEXIST) {
+ bd = backlight_device_get_by_name(name);
+ if (bd) {
+ put_device(&bd->dev);
+ /*
+ * Using the same name independent of the drm device or connector
+ * prevents registration of multiple backlight devices in the
+ * driver. However, we need to use the default name for backward
+ * compatibility. Use unique names for subsequent backlight devices as a
+ * fallback when the default name already exists.
+ */
kfree(name);
name = kasprintf(GFP_KERNEL, "card%d-%s-backlight",
i915->drm.primary->index, connector->base.name);
if (!name)
return -ENOMEM;
-
- bd = backlight_device_register(name, connector->base.kdev, connector,
- &intel_backlight_device_ops, &props);
}
+ bd = backlight_device_register(name, connector->base.kdev, connector,
+ &intel_backlight_device_ops, &props);

if (IS_ERR(bd)) {
drm_err(&i915->drm,
--
2.35.1