[Intel-gfx] [PATCHv3] drm/i915/display: add support for dual panel backlight

[Murthy, Arun R]

Gentle Reminder!

Thanks and Regard,
Arun R Murthy
--------------------

> -----Original Message-----
> From: Murthy, Arun R <arun.r.murthy at intel.com>
> Sent: Monday, August 8, 2022 9:28 AM
> To: intel-gfx at lists.freedesktop.org
> Cc: Nikula, Jani <jani.nikula at intel.com>; Murthy, Arun R
> <arun.r.murthy at intel.com>
> Subject: [PATCHv3] drm/i915/display: add support for dual panel backlight
> 
> The patch with commit 20f85ef89d94 ("drm/i915/backlight: use unique
> backlight device names") already adds support for dual panel backlight but
> with error prints. Since the patch tried to create the backlight device with the
> same name and upon failure will try with a different name it leads to failure
> logs in dmesg inturn getting caught by CI.
> 
> This patch alternately will check if the backlight class of same name exists,
> will use a different 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)
> 
> Signed-off-by: Arun R Murthy <arun.r.murthy at intel.com>
> ---
>  .../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 110fc98ec280..931446413372 100644
> --- a/drivers/gpu/drm/i915/display/intel_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_backlight.c
> @@ -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,
> --
> 2.25.1