Re: [PATCH] ACPI: video: Ignore BIOS initial backlight value for HP 250 G1

[Aaron Lu <aaron.lu@intel.com>]

On 10/18/2013 07:56 PM, Kirill Tkhai wrote:
> On HP 250 G1 laptops, BIOS reports minimum backlight on boot and
> causes backlight to dim completely. This ignores the initial backlight
> values and set to max brightness.
> 
> Reference: https://bugzilla.kernel.org/show_bug.cgi?id=63111

According to the acpidump:

The ASL code initialize initial brightness level to 100, but only for OS
that is pre-vista. Don't know why it does this...

Method (_INI, 0, NotSerialized)  // _INI: Initialize
{
	If (LLess (OSYS, 0x07D6))
	{
		Store (0x64, BRTL)
	}
	... ...
}

Method (_BQC, 0, NotSerialized)  // _BQC: Brightness Query Current
{
	Return (BRTL)
}

Since it is not initialized in _INI(as we report to firmware we are
'Windows 2012'), the video module was told by _BQC the initial brightness
level is 0 and then set backlight level to 0 and leads to a black screen
after boot up.

> Signed-off-by: Kirill Tkhai <tkhai@yandex.ru>

The patch looks good to me.
Reviewed-by: Aaron Lu <aaron.lu@intel.com>

Thanks,
Aaron

> ---
>  drivers/acpi/video.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
> index 3270d3c..6456466 100644
> --- a/drivers/acpi/video.c
> +++ b/drivers/acpi/video.c
> @@ -490,6 +490,14 @@ static struct dmi_system_id video_dmi_table[] __initdata = {
>  		DMI_MATCH(DMI_PRODUCT_NAME, "HP Pavilion m4 Notebook PC"),
>  		},
>  	},
> +	{
> +	 .callback = video_ignore_initial_backlight,
> +	 .ident = "HP 250 G1",
> +	 .matches = {
> +		DMI_MATCH(DMI_BOARD_VENDOR, "Hewlett-Packard"),
> +		DMI_MATCH(DMI_PRODUCT_NAME, "HP 250 G1 Notebook PC"),
> +		},
> +	},
>  	{}
>  };
>  
> --
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