This is a note to let you know that I've just added the patch titled drm/i915/display: avoid warnings when registering dual panel backlight to the 5.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: drm-i915-display-avoid-warnings-when-registering-dua.patch and it can be found in the queue-5.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 835b1daea701753c6df9f273d532e6ea949e5f56 Author: Arun R Murthy <arun.r.murthy@xxxxxxxxx> Date: Mon Aug 8 09:27:50 2022 +0530 drm/i915/display: avoid warnings when registering dual panel backlight [ 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@xxxxxxxxx> Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20220808035750.3111046-1-arun.r.murthy@xxxxxxxxx (cherry picked from commit 4234ea30051200fc6016de10e4d58369e60b38f1) Signed-off-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> 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,