Re: [PATCH] Revert "vgaarb: Keep adding VGA device in queue"

From: "Michel Dänzer" <michel-otUistvHUpPR7s880joybQ@public.gmane.org>
To: Daniel Vetter <daniel-/w4YWyX8dFk@public.gmane.org>,
	Alex Deucher
	<alexdeucher-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Alex Deucher <alexander.deucher-5C7GfCeVMHo@public.gmane.org>,
	Aaron Ma <aaron.ma-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>,
	amd-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org,
	dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org
Subject: Re: [PATCH] Revert "vgaarb: Keep adding VGA device in queue"
Date: Fri, 10 May 2019 17:46:43 +0200	[thread overview]
Message-ID: <58ea5dae-be17-af97-0066-48feab80497e@daenzer.net> (raw)
In-Reply-To: <20190510154208.GL17751-dv86pmgwkMBes7Z6vYuT8azUEOm+Xw19@public.gmane.org>

On 2019-05-10 5:42 p.m., Daniel Vetter wrote:
> On Fri, May 10, 2019 at 09:29:58AM -0500, Alex Deucher wrote:
>> This breaks multiple graphics cards in the Amigaone x5000
>> on PPC.
>>
>> This reverts commit 3d42f1ddc47a69c0ce155f9f30d764c4d689a5fa.
>>
>> Bug: https://bugs.freedesktop.org/show_bug.cgi?id=109345
>> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
>> CC: Aaron Ma <aaron.ma@canonical.com>
> 
> Given that the bug is a bit a mess I think we need to add a bit more
> context here in the commit message. My understanding:
> 
> Goal of the revert commit was to make the integrated boot device the
> primary one, if we can't detect which one is the boot device, instead of
> the last one. Which makes some sense.
> 
> Now people have relied on the kernel picking the last one, which usually
> is an add-on card, and therefore simply plugging in an add-on card allows
> them to overwrite the default choice. Which also makes sense, and since
> it's the older behaviour, wins.
> 
> I think it'd be good to add a comment here that this behaviour has become
> uapi, e.g.
> 
> 	/* Add at the front so that we pick the last device as fallback
> 	 * default, with the usual result that plug in cards are preferred
> 	 * over integrated graphics. */
> 
> With that (or similar) and more commit message context:

The bug reporter's system doesn't have integrated graphics though, just
two plug-in cards. It's not clear to me yet that their expectation of
Xorg to pick any particular one of them without configuration was justified.

-- 
Earthling Michel Dänzer               |              https://www.amd.com
Libre software enthusiast             |             Mesa and X developer
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