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Date:	Fri, 14 Feb 2014 15:16:58 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	linux-acpi@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <lenb@...nel.org>, Aaron Lu <aaron.lu@...el.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Revert "ACPI / video: Add HP EliteBook Revolve 810 to the blacklist"

At Fri, 14 Feb 2014 16:16:52 +0200,
Mika Westerberg wrote:
> 
> On Fri, Feb 14, 2014 at 03:01:21PM +0100, Takashi Iwai wrote:
> > At Fri, 14 Feb 2014 16:03:16 +0200,
> > Mika Westerberg wrote:
> > > 
> > > On Fri, Feb 14, 2014 at 02:37:00PM +0100, Takashi Iwai wrote:
> > > > At Fri, 14 Feb 2014 14:34:07 +0200,
> > > > Mika Westerberg wrote:
> > > > > 
> > > > > This reverts commit e18ac62fa4b3f16234bab0d5a6627c57dbae9e7e.
> > > > > 
> > > > > The referenced commit added HP EliteBook Revolve 810 to the ACPI video
> > > > > detected blacklist so that only the native Intel backlight interface was
> > > > > exported.
> > > > > 
> > > > > However, this turned to be wrong solution after all. The ACPI video
> > > > > interface works and as long as we only use that there are no problems. So
> > > > > we can revert this commit and stick to use the backlight interface provided
> > > > > by the ACPI video driver.
> > > > > 
> > > > > (Using Intel native interface will not work after resume since the ACPI
> > > > > video driver will restore it's state which takes control over the native
> > > > > one. That's a separate thing and should be addressed in the ACPI video
> > > > > driver, I suppose.)
> > > > > 
> > > > > References: https://bugzilla.kernel.org/show_bug.cgi?id=70231
> > > > > Cc: Aaron Lu <aaron.lu@...el.com>
> > > > > Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> > > > > ---
> > > > > Rafael, 
> > > > > 
> > > > > This turned out to be misunderstanding from my side. I should have
> > > > > investigated this further before submitting the original patch. Sorry about
> > > > > that.
> > > > > 
> > > > > Aaron,
> > > > > 
> > > > > Thanks for the investigation and pointing me to the right direction (e.g to
> > > > > use acpi_video0 over the native one).
> > > > 
> > > > Could you check whether the ACPI video still really works even if you
> > > > remove the recent acpi_osi blacklist entry below?  It might be that
> > > > BIOS changed its mind to behave more kindly as if handling for Win7.
> > > > 
> > > > 
> > > > Takashi
> > > > 
> > > > ---
> > > > diff --git a/drivers/acpi/blacklist.c b/drivers/acpi/blacklist.c
> > > > index 10e4964d051a..64d14406465d 100644
> > > > --- a/drivers/acpi/blacklist.c
> > > > +++ b/drivers/acpi/blacklist.c
> > > > @@ -322,6 +322,7 @@ static struct dmi_system_id acpi_osi_dmi_table[] __initdata = {
> > > >  		     DMI_MATCH(DMI_PRODUCT_VERSION, "2349D15"),
> > > >  		},
> > > >  	},
> > > > +#if 0
> > > >  	{
> > > >  	.callback = dmi_disable_osi_win8,
> > > >  	.ident = "HP ProBook 2013 models",
> > > > @@ -372,6 +373,7 @@ static struct dmi_system_id acpi_osi_dmi_table[] __initdata = {
> > > >  		     DMI_MATCH(DMI_PRODUCT_NAME, "HP EliteBook 8780w"),
> > > >  		},
> > > >  	},
> > > > +#endif
> > > >  
> > > >  	/*
> > > >  	 * BIOS invocation of _OSI(Linux) is almost always a BIOS bug.
> > > 
> > > After this patch is applied, the ACPI backlight doesn't work anymore. The
> > > brightness stays the same, no matter what I do.
> > 
> > So, you need the video blacklist when acpi_osi blacklist doesn't
> > exist, right?
> 
> In my case I don't actually need video blacklist if I use only ACPI video
> for backlight control. Then it works fine.

Hmm, after removing acpi_osi blacklist above, you loose the ACPI video
backlight doesn't work, no?  If so, you need the video blacklist.
Am I missing anything obvious...?

> However, using intel_backlight will cause ACPI video to restore its
> settings over the Intel one on resume.

I guess the very reason why ACPI video backlight doesn't work in Win8
BIOS mode -- ACPI video won't conflict the native backlight.


Takashi
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