From: Vincent Blut <vincent.debian@free.fr>
Subject: Re: [REGRESSION/PATCH] acpi: blacklist win8 OSI for ASUS Zenbok
 Prime UX31A
Date: Mon, 21 Oct 2013 00:16:28 +0200
Message-ID: <1382307388.4030.30.camel@lamella>
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Sender: linux-acpi-owner@vger.kernel.org
To: linux-acpi@vger.kernel.org
Cc: felipe.contreras@gmail.com, rafael.j.wysocki@intel.com


> Since v3.7 the acpi backlight driver doesn't work at all on this mach=
ine
> because presumably the ACPI code contains stub code when Windows 8 OS=
I is
> reported.
>=20
> 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 com=
pletely
> off when it reaches level 0%, after which the user might have a lot t=
rouble
> trying to bring it back.
>=20
> 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 backl=
ight
> driver is fixed.
>=20
> Since v3.7, users have been forced to fix the initial regression by m=
odifying
> the boot arguments [1].
>=20
> [1] https://wiki.archlinux.org/index.php/ASUS_Zenbook_Prime_UX31A
>=20
> Signed-off-by: Felipe Contreras <felipe.contreras@xxxxxxxxx>
> ---
>  drivers/acpi/blacklist.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>=20
> 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 str=
uct 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;
> +}
> =20
>  static struct dmi_system_id acpi_osi_dmi_table[] __initdata =3D {
>  	{
> @@ -267,6 +273,14 @@ static struct dmi_system_id acpi_osi_dmi_table[]=
 __initdata =3D {
>  		     DMI_MATCH(DMI_PRODUCT_NAME, "Satellite P305D"),
>  		},
>  	},
> +	{
> +	.callback =3D dmi_disable_osi_win8,
> +	.ident =3D "ASUS Zenbook Prime UX31A",
> +	.matches =3D {
> +		     DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
> +		     DMI_MATCH(DMI_PRODUCT_NAME, "UX31A"),
> +		},
> +	},
> =20
>  	/*
>  	 * BIOS invocation of _OSI(Linux) is almost always a BIOS bug.
> --=20
> 1.8.3.4

=46elipe, Rafa=C3=ABl,

I wonder if this quirk is still needed=E2=80=BD I'm the owner of an Asu=
s UX31A and of course,
I used to set acpi_osi=3D"!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=20
least inhibited) the issue:

commit	efaa14c7e981bdf8d3c8d39d3ed12bdc60faabb8
ACPI / video: no automatic brightness changes by win8-compatible firmwa=
re

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=3D702188


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