From: Daniel Vetter <firstname.lastname@example.org>
To: Thomas Zimmermann <email@example.com>
Cc: Mikulas Patocka <firstname.lastname@example.org>,
Linux Fbdev development list <email@example.com>,
Geert Uytterhoeven <firstname.lastname@example.org>,
Jonathan Corbet <email@example.com>,
Linux Doc Mailing List <firstname.lastname@example.org>,
Bernie Thompson <email@example.com>,
Sam Ravnborg <firstname.lastname@example.org>
Subject: Re: [PATCH] fbdev: Remove udlfb driver
Date: Wed, 2 Dec 2020 18:52:04 +0100 [thread overview]
Message-ID: <CAKMK7uF+uu3taQL-FPXymvnVhKyWWtNy9Z2xes=+j-B+BHaTgA@mail.gmail.com> (raw)
On Wed, Dec 2, 2020 at 8:55 AM Thomas Zimmermann <email@example.com> wrote:
> Am 01.12.20 um 12:20 schrieb Mikulas Patocka:
> > On Tue, 1 Dec 2020, Thomas Zimmermann wrote:
> >> Hi
> >> Am 30.11.20 um 19:39 schrieb Mikulas Patocka:
> >>> On Mon, 30 Nov 2020, Daniel Vetter wrote:
> >>>> On Mon, Nov 30, 2020 at 09:31:15AM -0500, Mikulas Patocka wrote:
> >>>>> The framebuffer driver supports programs running full-screen directly on
> >>>>> the framebuffer console, such as web browser "links -g", image viewer
> >>>>> "fbi", postscript+pdf viewer "fbgs", ZX Spectrum emulator "fuse-sdl",
> >>>>> movie player "mplayer -vo fbdev". The DRM driver doesn't run them.
> >>>> Hm this should in general work on drm drivers. Without that it's clear the
> >>>> switch-over isn't really ready yet.
> >>> I fixed it with this patch two years ago:
> >>> https://lists.freedesktop.org/archives/dri-devel/2018-June/179023.html
> >>> But the patch never went through and the fb_defio feature was removed in
> >>> the kernel 5.6 (commit d0c4fc5a4814e431c15272935c8dc973c18073aa).
> >>> Without fb_defio, the only other possibility how to update the screen is
> >>> the ioctl DRM_IOCTL_MODE_DIRTYFB. But this ioctl requires master mode, so
> >>> user programs like "links -g" can't issue it.
> >> That's confusing. DIRTYFB is only for DRM.
> > Yes, you're right.
> >> And why can links not run as DRM master mode? If it renders to the terminal,
> >> it should act like a composer. In that case it almost certainly wants master
> >> status.
> >> Best regards
> >> Thomas
> > How can a userspace program acquire master mode without being suid?
> For my understanding, there's no easy solution to that. :/
If you're absolutely the only thing running, the first one to open the
card* node wins. But usually you have something like logind managing
this for you (for vt switching), since ad-hoc this is a very fragile
I'm not exactly sure how logind gives you an already opened drm device
in master mode, that's a bit tricky. Without either being suid root or
participating in the logind scheme you won't be able to vt switch
But bare metal kms usage should work I as-is.
> I guess we (DRM devs) have to treat fbdev as the solution for use cases
> such as ours.
> For the unplug issue, I'll try to reproduce and fix it.
> For the performance problems, we might be able to squeeze a few more
> cycles out of it.
> Best regards
> > Is there some "Hello World!" program that shows how to use DRM? I'm not an
> > expert in DRM, but if there were some tutorial+documentation, I could
> > consider porting "links" to it.
> > Mikulas
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Maxfeldstr. 5, 90409 Nürnberg, Germany
> (HRB 36809, AG Nürnberg)
> Geschäftsführer: Felix Imendörffer
Software Engineer, Intel Corporation
next prev parent reply other threads:[~2020-12-02 17:52 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-30 12:52 [PATCH] fbdev: Remove udlfb driver Thomas Zimmermann
2020-11-30 14:31 ` Mikulas Patocka
2020-11-30 15:41 ` Daniel Vetter
2020-11-30 18:39 ` Mikulas Patocka
2020-11-30 21:06 ` Daniel Vetter
2020-12-01 11:26 ` Mikulas Patocka
2020-12-01 8:07 ` Thomas Zimmermann
2020-12-01 11:20 ` Mikulas Patocka
2020-12-02 7:55 ` Thomas Zimmermann
2020-12-02 8:01 ` Thomas Zimmermann
2020-12-02 8:29 ` Pekka Paalanen
2020-12-02 17:52 ` Daniel Vetter [this message]
2020-12-01 8:02 ` Thomas Zimmermann
2020-12-01 10:44 ` Mikulas Patocka
2020-12-01 20:09 ` Mikulas Patocka
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