linux-kernel - Re: [PATCH] drm/i915/opregion: work around buggy firmware that provides 8+ output devices

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Date:	Wed, 19 Feb 2014 16:59:06 +0800
From:	Aaron Lu <aaron.lu@...el.com>
To:	Matthew Garrett <mjg59@...f.ucam.org>
CC:	Daniel Vetter <daniel.vetter@...ll.ch>,
	Chris Wilson <chris@...is-wilson.co.uk>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Oleksij Rempel <linux@...pel-privat.de>,
	"intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	ACPI Devel Mailing List <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH] drm/i915/opregion: work around buggy firmware that provides
 8+ output devices

On 02/19/2014 03:33 PM, Matthew Garrett wrote:
> On Wed, Feb 19, 2014 at 03:31:29PM +0800, Aaron Lu wrote:
> 
>> DID2 is in system memory region and has some assigned value like 0x400
>> when we read it. For this case it is easy since there is only one output
>> device that is of type LVDS so we can match it to connector of type eDP
>> or LVDS, suppose there is only one such connector. But for output
>> devices' whose _ADR has the value of 0x301, 0x302, etc. I have no idea
>> how to match them up to the connectors of that type as we can't be sure
>> the probe order we have used in i915 driver is the same as BIOS'.
> 
> Non-standard _ADR values are assigend by the GPU vendor, so Intel should 
> be able to provide you with the correct interpretations.

It doesn't seem the _ADR value has to be the format defined by _DOD, as
the example of the ACPI spec gives:
Method (_ADR, 0) {
    return(0x0100)
}
So that is not the problem here.

The problem is, we don't have any way of matching an ACPI output device
node to a drm connector of the same type when there are more than 1 of
those with the same type, i.e. we don't know how the index value are
assigned by BIOS.
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