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

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

On 10/22/2013 05:21 AM, Vincent Blut wrote:
> Le 21/10/2013 03:53, Aaron Lu a écrit :
>> On 10/21/2013 06:16 AM, Vincent Blut wrote:
>>>
>>>> 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?
>>
>> I don't think ASUS UX31A needs that quirk anymore.
> 
> Hi Aaron,
> 
> Thanks for your answer. Btw I'd like to know if there is a reason that
> you didn't cc your patch (commit efaa14c7) to <stable@vger.kernel.org>,
> however I didn't test if it'd apply cleanly!

In addition to solve the backlight issue for some systems, that commit
is also a behavior change regarding how backlight level should be
handled when user plugs in/out the AC adapter, so I didn't specify the
stable tag.

Thanks,
Aaron
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