On Wed, Dec 2, 2020 at 8:55 AM Thomas Zimmermann <tzimmermann@xxxxxxx> wrote: > > Hi > > 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 scheme. 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 though. But bare metal kms usage should work I as-is. -Daniel > > 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) > Geschäftsführer: Felix Imendörffer > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
