Re: [REGRESSION/PATCH] acpi: blacklist win8 OSI for ASUS Zenbok Prime UX31A

[Vincent Blut <vincent.debian@free.fr>]

> Since v3.7 the acpi backlight driver doesn't work at all on this machine
> because presumably the ACPI code contains stub code when Windows 8 OSI is
> reported.
> 
> The commit ea45ea7 (in v3.11-rc2) tried to fix this problem by using the intel
> backlight driver, however, on this machine it turns the backlight completely
> off when it reaches level 0%, after which the user might have a lot trouble
> trying to bring it back.
> 
> This patch fixes both regressions by blacklisting the win8 OSI, so we are back
> to v3.6 behavior, and it should remain that way until the intel backlight
> driver is fixed.
> 
> Since v3.7, users have been forced to fix the initial regression by modifying
> the boot arguments [1].
> 
> [1] https://wiki.archlinux.org/index.php/ASUS_Zenbook_Prime_UX31A
> 
> Signed-off-by: Felipe Contreras <felipe.contreras@xxxxxxxxx>
> ---
>  drivers/acpi/blacklist.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/acpi/blacklist.c b/drivers/acpi/blacklist.c
> index cb96296..a404127 100644
> --- a/drivers/acpi/blacklist.c
> +++ b/drivers/acpi/blacklist.c
> @@ -192,6 +192,12 @@ static int __init dmi_disable_osi_win7(const struct dmi_system_id *d)
>  	acpi_osi_setup("!Windows 2009");
>  	return 0;
>  }
> +static int __init dmi_disable_osi_win8(const struct dmi_system_id *d)
> +{
> +	printk(KERN_NOTICE PREFIX "DMI detected: %s\n", d->ident);
> +	acpi_osi_setup("!Windows 2012");
> +	return 0;
> +}
>  
>  static struct dmi_system_id acpi_osi_dmi_table[] __initdata = {
>  	{
> @@ -267,6 +273,14 @@ static struct dmi_system_id acpi_osi_dmi_table[] __initdata = {
>  		     DMI_MATCH(DMI_PRODUCT_NAME, "Satellite P305D"),
>  		},
>  	},
> +	{
> +	.callback = dmi_disable_osi_win8,
> +	.ident = "ASUS Zenbook Prime UX31A",
> +	.matches = {
> +		     DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
> +		     DMI_MATCH(DMI_PRODUCT_NAME, "UX31A"),
> +		},
> +	},
>  
>  	/*
>  	 * BIOS invocation of _OSI(Linux) is almost always a BIOS bug.
> -- 
> 1.8.3.4

Felipe, Rafaël,

I wonder if this quirk is still needed‽ I'm the owner of an Asus UX31A and of course,
I used to set acpi_osi="!Windows 2012" on the kernel command line in order to change
the backlight level. *However* since Linux 3.11, this kernel parameter is not needed
anymore to influence it. The following commit seems to be the one that fixed (or at 
least inhibited) the issue:

commit	efaa14c7e981bdf8d3c8d39d3ed12bdc60faabb8
ACPI / video: no automatic brightness changes by win8-compatible firmware

Indeed, I reverted it on top of 3.11.6 and I can't change the backlight level anymore
on this system!

Please see [1] for more information on what does that commit change in the way to control
the backlight level.

So, is this inherent to my system? thought?

Cheers,
Vincent

[1]http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=702188



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