linux-kernel - Re: Standard VGA console with DRI/DRM under X?

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Message-ID: <CAErSpo4zDxhG08FjyV9BJ+=cJLGYkyocz87ZRWndw70ND3g6XA@mail.gmail.com>
Date:	Tue, 28 Oct 2014 09:48:28 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Michael Shell <list1@...haelshell.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	David Airlie <airlied@...ux.ie>,
	DRI mailing list <dri-devel@...ts.freedesktop.org>,
	Alex Deucher <alexander.deucher@....com>,
	Christian König <christian.koenig@....com>
Subject: Re: Standard VGA console with DRI/DRM under X?

[+cc David, Alex, Christian, dri-devel]

On Tue, Oct 28, 2014 at 12:32 AM, Michael Shell <list1@...haelshell.org> wrote:
>
>
>   Greetings,
>
> Well, I want to be able to have my cake and eat it too. I want to be able to
> have the standard VGA/"hardware" classic console (not the framebuffer) but
> I still want the /dev/dri/cardX devices so that I can use DRI under Xorg.
>
> Is this possible and if not, why not?
>
>
> (I do hope I'm not bring up an issue with an obvious fix, but my searching
>  has not yielded an answer yet. For the record, I'm running modern kernel
>  (3.16.3) with much older x86 hardware [r100 Radeon video card].)
>
>
> If I boot with the kernel nomodeset option I can get the classic
> VGA/"hardware" console, but then I lose support for DRI/DRM:
>
> Oct 27 15:11:09 X kernel: [drm] Initialized drm 1.1.0 20060810
> Oct 27 15:11:09 X kernel: [drm] VGACON disable radeon kernel modesetting.
> Oct 27 15:11:09 X kernel: [drm:radeon_init] *ERROR* No UMS support in radeon module
>
> and glxgears et al. turns slow. In more modern Xorg releases, DRI is
> required for all hardware acceleration, so having /dev/dri/cardX is very
> important:
>
> http://askubuntu.com/questions/463142/why-x-is-relying-on-software-instead-of-hardware-with-nomodeset-kernel-paramet
>
>
> One reason I do not wish to use the framebuffer console is because of the
> small font. 160 columns makes it difficult to tell which [OK] belongs with
> which service. The selection of console fonts should always include a
> set that gives us an 80 column screen and the docs should point this out.
>
> And I dislike any blanking or video mode changes during boot.
>
> Can't the kernel just declare that it is capable of setting the video mode,
> provide the /dev/dri/cardX devices and leave the console alone, but still
> allow Xorg to call for a new mode and use /dev/dri/cardX if/when it sees fit?
>
> In an ideal world, there would be some kernel option such as fbcon=no.
>
> In the kernel Documentation fbcon.txt it mentions "fbcon=map:1 tells fbcon not
> to take over the console." But, IIRC, from my tests I wasn't able to use this
> to get a VGA/"hardware" console and still be able to have /dev/dri/cardX devices.
>
>
>
>     Cheers and thank you,
>
>     Mike Shell
> --
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