linux-kernel - Re: [PATCH 5/5] ACPI: Tie ACPI backlight devices to PCI devices if possible

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Message-ID: <20110207213426.GA23843@srcf.ucam.org>
Date:	Mon, 7 Feb 2011 21:34:26 +0000
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Bjorn Helgaas <bjorn.helgaas@...com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, dri-devel@...ts.freedesktop.org,
	akpm@...ux-foundation.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, rpurdie@...ys.net,
	Len Brown <lenb@...nel.org>
Subject: Re: [PATCH 5/5] ACPI: Tie ACPI backlight devices to PCI devices if
	possible

On Mon, Feb 07, 2011 at 02:32:35PM -0700, Bjorn Helgaas wrote:

> I'm not familiar with video devices, but I agree, this situation does
> feel broken.  Is it the case that there's a PCI device as well as an
> ACPI namespace Device for the same piece of hardware?  If so, I assume
> the reason for the ACPI Device is to have a "standard" interface to
> a platform knob like backlight control.
> 
> In that case, it seems like we should rely on PCI for enumeration and
> driver binding, have some sort of hook the PCI driver could use to
> twiddle that knob (using the ACPI methods), and make the ACPI Device
> ineligible for driver binding.  In other words, it sounds like part
> of the problem is that we have two drivers binding to what's really
> a single piece of hardware.

Part of the problem is that ACPI video devices aren't inherently PCI 
devices.

-- 
Matthew Garrett | mjg59@...f.ucam.org
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