linux-kernel - Re: [PATCH] Add Intel ACPI IGD OpRegion support

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Message-ID: <20080806122914.GB12783@khazad-dum.debian.net>
Date:	Wed, 6 Aug 2008 09:29:14 -0300
From:	Henrique de Moraes Holschuh <hmh@....eng.br>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	Yves-Alexis Perez <corsac@...ian.org>, airlied@...ux.ie,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH] Add Intel ACPI IGD OpRegion support

Hi Matthew!

On Wed, 06 Aug 2008, Matthew Garrett wrote:

> On Tue, Aug 05, 2008 at 11:32:48PM -0300, Henrique de Moraes Holschuh wrote:
> > On Wed, 06 Aug 2008, Matthew Garrett wrote:
> > > The 750ms delay is from thinkpad-acpi. I sent a patch to Henrique which 
> > > makes it go away, but I'm not entirely sure what the ACPI method 
> > > concerned is supposed to be doing. The opregion code won't currently run 
> > > until X is started because the drm layer requires X to be the foreground 
> > > vt before handling IRQs.
> > 
> > Well, for what is it worth, thinkpad-acpi has a knob (brightness_mode) which
> > can be used.  Set it to CMOS mode (see docs).  From what I recall, it should
> > do what your patch does.
> 
> It doesn't seem to, no. I should have been clearer - the delay is in the 
> DSDT (not thinkpad-acpi itself), but there's a Thinkpad-specific ACPI 
> call that seems to be needed in order to delay it. Here's the patch 
> again.
> 
> diff --git a/drivers/misc/thinkpad_acpi.c b/drivers/misc/thinkpad_acpi.c
> index b596929..bbc45c8 100644
> --- a/drivers/misc/thinkpad_acpi.c
> +++ b/drivers/misc/thinkpad_acpi.c
> @@ -899,6 +899,9 @@ static int __init tpacpi_check_std_acpi_brightness_support(void)
>  
>  	if (ACPI_SUCCESS(status) && bcl_levels > 2) {
>  		tp_features.bright_acpimode = 1;
> +		/* Set ACPI mode */
> +		if (!acpi_evalf(hkey_handle, NULL, "PWMS", "vd", 0))
> +			printk(TPACPI_INFO "Failed to claim backlight\n");
>  		return (bcl_levels - 2);
>  	}

Ah, THIS patch.  Yes, a more intelligent version of it (that doesn't scream
blood murder on thinkpads without PWMS) needs to go into thinkpad-acpi
along with your patch.

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh
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