[alsa-devel] [PATCH 2/4] acpi: allow for an override to set _REV

[Mario Limonciello]

On 05/21/2015 01:10 PM, Matthew Garrett wrote:
> On Wed, May 20, 2015 at 6:24 PM, Rafael J. Wysocki <rjw at rjwysocki.net> wrote:
>
>> Which doesn't explain why we need a config option per quirk.  To me, such config
>> options don't add any value, because (a) everyone will set them anyway and (b)
>> removing the quirks from the source is trivial if needed.
> We'd disable this quirk in Fedora the moment jack detection works,
> because we've got the userspace to handle it and using I2S is
> preferable to using HDA - but in doing so we might break battery
> detection on the other Dell that's playing _REV tricks. This seems
> like a suboptimal choice to have to make.

Having dug into this deeper with you on the other thread, battery 
detection already wasn't working.
That machine did the _REV test and fix for Linux only on Windows 2009 
_OSI and the _REV value of 5.
The kernel currently responds to a later _OSI that the machine supports 
so that AML does not get run.

I believe battery detection may be fixed on that Inspiron by 
75646e758a0ecbed5024454507d5be5b9ea9dcbf.
if it's not, that's a tangential problem that should be fixed to match 
the Windows behavior for battery detection.