Fbdev-backend removal from Weston (Re: Upcoming release)

[nerdopolis]

On Wednesday, January 23, 2019 4:09:44 AM EST Pekka Paalanen wrote:
> On Tue, 22 Jan 2019 22:46:02 -0500
> nerdopolis <bluescreen_avenger at verizon.net> wrote:
> 
> > On Tuesday, January 22, 2019 9:55:15 AM EST Pekka Paalanen wrote:
> 
> > > 
> > > On Tue, 22 Jan 2019 10:17:32 +0200
> > > Pekka Paalanen <ppaalanen at gmail.com> wrote:
> > >   
> > > > Hi,
> > > > 
> > > > do you actually have a use case for that? It's ok if you do, we can
> > > > keep it around for some more, but the simple fact that some hardware
> > > > exists that does not have a working DRM driver is not enough. There
> > > > should be users too.
> > > > 
> > > > The fbdev-backend certainly has its shortcomings, and I don't mean just
> > > > the lack of multi-output or monitor hotplug or GPU acceleration or
> > > > tearing or timings based on nothing but timers; I recall VT-switching
> > > > being broken for years now, and it doesn't (cannot?) use logind to open
> > > > the FB devices. Did I forget some?
> 
> > 
> > Hi
> > 
> > Well, TBH, It's just my quazi-distribution Live CD that I still maintain...
> > It falls back to the Framebuffer on systems (or seats) that don't have 
> > Kernel Mode Setting. The number of users now probably is low...
> 
> Right. Would you be able to do a test? Disable fbdev on your distro and
> see if anyone complains?
> 
TBH, the user base is likely not as high as it was in 2012. It's prime focus
was to allow users to test anything Wayland live. So I don't think that would
be a good way to tell, since now there are other more popular ways people have
been using it now.
> In fact, would be nice if all distributions did that test. I'm not in
> that much hurry to delete the backend yet.
> 
> > VT switching works great. It works without weston-launch, and I can switch away
> > to a second instance of Weston using the Framebuffer, without them stepping on
> > each other, and I can switch back to the original one, and it continues working
> > 
> > I do have to create a udev file that sets
> > SUBSYSTEM=="graphics", KERNEL=="fb*", TAG+="uaccess"
> > though...
> 
> Yes, that rule or similar is required because logind does not deal fb
> devices IIRC and Weston certainly doesn't ask.
> 
> Are you relying on logind or running Weston privileged to have VT
> switching working?
> 
I am making no changes to logind. I am not running Weston as root. I am not
even granting the plugdev group access to the /dev/fbX devices (It's a "hidden"
boot option, disabled by default). Just systemd-run that starts it as a User
account.
> It's been a long time since I tried VT-switching with fbdev, but it
> didn't work with logind back then:
> https://gitlab.freedesktop.org/wayland/weston/issues/78
> Could it have been fixed in logind instead?
>
Yeah, I wasnt even aware of that one. It was probably logind. Weston is working
fine. I can switch between the framebuffer backed login greeter, and a frame
buffer backed login session, and they don't draw on each other. Weston even
logs when the session becomes active and inactive, so it is aware.

It even works on seats that do NOT have TTYs, since my login manager is
multiseat aware now, I can test that :)
> 
> Thanks,
> pq