On Wed, 2 Dec 2020 08:55:52 +0100 Thomas Zimmermann <tzimmermann@xxxxxxx> wrote: > Hi > > Am 01.12.20 um 12:20 schrieb Mikulas Patocka: > > > > > > On Tue, 1 Dec 2020, Thomas Zimmermann wrote: > > ... > >> 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. :/ Hi, there are several ways, though whether they are "easy" depends on your mindset. The best thing is to connect to logind D-Bus API and ask that for session control, set up your session, and logind will open all input and DRM devices for you, and logind will even handle most of the complicated setup, DRM master and VT-switching for you. Or, if no-one else has the DRM device open and you open it, you automatically become DRM master. AFAIU, after recent kernel changes, it is even possible to use dropMaster and setMaster after this without being root, as long as you once in the file description lifetime had DRM master. Since this is about switching from fbdev to KMS API, you already have all the tricky, complicated, arcane code to deal with tty setup and VT-switching. However, doing all that patching to all apps you want to use is such an effort, that I'd ask if it would not be easier to just run a light-weight Wayland compositor and run your apps in Wayland mode. Of course, that requires choosing apps that run on Wayland to begin with, so maybe it's not for you. Thanks, pq
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