Re: [PATCH] fbdev: Remove udlfb driver

Hi

Am 01.12.20 um 12:20 schrieb Mikulas Patocka:

On Tue, 1 Dec 2020, Thomas Zimmermann wrote:

quoted

Hi

Am 30.11.20 um 19:39 schrieb Mikulas Patocka:

quoted

On Mon, 30 Nov 2020, Daniel Vetter wrote:

quoted

On Mon, Nov 30, 2020 at 09:31:15AM -0500, Mikulas Patocka wrote:

quoted

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.

quoted

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. :/

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
Thomas

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)
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