Re: [RFC PATCH] thinkpad-acpi: Improve hardware volume controls

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On Mon, May 9, 2011 at 10:36 PM, Andrew Lutomirski <luto@xxxxxxx> wrote:
> On Mon, May 9, 2011 at 9:04 PM, Henrique de Moraes Holschuh
> <hmh@xxxxxxxxxx> wrote:
>> On Mon, 09 May 2011, Andrew Lutomirski wrote:
>>> FWIW, this patch (other than having the wrong default on X220) makes
>>> Linux better than Windows :)
>>
>> Please expand on that, especially the "wrong default on X220"...
>>
>>> Do you know how to read a field from the EC by name?  I think I can
>>
>> If it is in the DSDT as a field of a "EmbeddedController" area, you just
>> evaluate it.  There are several examples in the driver (e.g. the TMP* evals
>> in the thermal monitor subdriver).
>
> Indeed :)  I'll send an updated patch tomorrow.
>
>>
>>> Also, do you know how to ask the kernel what the most recent acpi
>>> interrupt was?  I'd like to find a better way to detect the mute
>>> button than watching for the keyboard event.
>>
>> No, and I'd never ACK it if there was one.  ACPI serves GPEs (interrupts)
>> like crazy for random reasons,  Never ever play racy games like that.
>>
>> Don't we get an HKEY notification for mute presses in the X220?
>
> I just meant to figure out what's going on.  We're not getting an HKEY
> event, I think, but something's happening and a bit of acpi debug
> fiddling says that _Q43 is getting called.  I have no idea what that
> means, though.

I read some more of the spec.  It looks like the EC sends query 43
when the mute status changes.

The problem is that _Q43 just calls _UCMS, which issues an SMI but
does nothing else.  So we don't get notified.  And unless we change
acpi_ec_sync_query to allow more than one handler for the same query,
we can't even get notified without breaking _Q43.  So we're screwed.

I guess relying on the keyboard event isn't *that* bad.

--Andy

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