From: Thomas Zimmermann <tzimmermann@suse.de>
To: stsp <stsp2@yandex.ru>,
linux-fbdev@vger.kernel.org,
Linux kernel <linux-kernel@vger.kernel.org>
Subject: Re: drmfb console switching problems/questions
Date: Fri, 09 Oct 2020 11:59:24 +0000 [thread overview]
Message-ID: <df4d1918-dcb1-4951-6280-f178ecbbfc2f@suse.de> (raw)
In-Reply-To: <17980f58-c2d2-ac58-88ce-e21b5a56da39@yandex.ru>
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Hi
Am 09.10.20 um 12:50 schrieb stsp:
> Hi!
>
> I am trying to run my sdl1-based app
> under linux kms framebuffer (amdgpudrmfb
> in my case).
> The app itself works perfectly, but
> console switching is not.
>
> If I switch the console while the app
> is drawing, then it will corrupt the
> VC I switched to. It will just draw on
> top of the VC's content.
> Question: is this expected? Is drm
> framebuffer global, rather than per-vc?
> If so, should I somehow freeze my
> app when it is switched away? And
> why would it be the case, with the
> modern video cards that have multi
> gigas of RAM on board?
>
> If my app crashes without a clean
> shutdown, then the framebuffer kinda
> hangs. I can switch to other VCs but
> I don't see their content. All I see is
> the last drawing of my app. If I happen
> to have an X server on some other VC,
> then switching to it immediately unhangs
> everything, and I can switch back.
> In fact, even if I hit Ctrl-Alt-Del, then
> fb immediately unhangs (by systemd
> or plymouth or whoever else). But for
> example SAK combo doesn't unhang.
> So it seems to be very simple to hang
> the framebuffer, and is quite difficult
> to recover.
> Question: is this an expected behaviour
> or a drmfb bug?
Fbdev exposes the video ram (or a shadow buffer of it) to all
applications. Only one can draw at the same time. It's a limitation of
the design. To fix this, your application has to stop drawing when you
switch consoles.
Best regards
Thomas
>
> Thanks!
>
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer
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next prev parent reply other threads:[~2020-10-09 11:59 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-09 10:50 drmfb console switching problems/questions stsp
2020-10-09 11:59 ` Thomas Zimmermann [this message]
2020-10-09 12:16 ` stsp
2020-10-09 12:58 ` Thomas Zimmermann
2020-10-09 13:19 ` stsp
2020-10-09 13:31 ` Thomas Zimmermann
2020-10-09 14:14 ` stsp
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