[PATCH] fbdev: Remove udlfb driver

[Mikulas Patocka]

On Mon, 30 Nov 2020, Daniel Vetter wrote:

> On Mon, Nov 30, 2020 at 01:39:17PM -0500, Mikulas Patocka wrote:
> > 
> > 
> > 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).
> 
> The generic fbdev emulation still has a defio implementation. We could try
> to make it more efficient maybe, but it should be all there. The module
> option disappeared since you now should always get it by default.

Yes, it's there. I've tried to run links on the current DRM UDL driver and 
it displays correctly - except, that the page list gets sometimes 
corrupted and a crash happens.

> > 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.
> 
> Now I'm confused, I thought you wanted to use fbdev /dev/fb* nodes? Those
> should support defio. And if you want your applications to use drm
> modesetting natively, they have to be drm master anyway. You can't use the
> DIRTYFB ioctl to upload fbdev contents. So I'm a bit confused.
> -Daniel

Yes. I was confused about it too. You can't use DRM ioctls on /dev/fb.

Mikulas