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drm/i915/display: avoid warnings when registering dual panel backlight 

Commit 20f85ef89d ("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 20f85ef89d
("drm/i915/backlight: use unique backlight device names")
v3: fixed the ref count leak(Jani N)

Fixes: 20f85ef89d ("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 4234ea3005)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
This commit is contained in:
Arun R Murthy 2022-08-08 09:27:50 +05:30 committed by Rodrigo Vivi
parent 875c6d2711
commit 2c4e19f873
1 changed files with 12 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
drivers/gpu/drm/i915/display/intel_backlight.c
View File

@ -971,26 +971,24 @@ 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,