[git pull] drm udl fixes

[Mikulas Patocka]

On Tue, 4 Sep 2018, Daniel Vetter wrote:

> On Tue, Sep 4, 2018 at 7:04 PM, Mikulas Patocka <mpatocka at redhat.com> wrote:
> >
> >
> > On Tue, 4 Sep 2018, Daniel Vetter wrote:
> >
> >> On Tue, Sep 4, 2018 at 1:41 AM, Dave Airlie <airlied at gmail.com> wrote:
> >> >>
> >> >> I've seen that you dropped this patch:
> >> >> https://patchwork.kernel.org/patch/10445393/
> >> >>
> >> >> Is that patch correct or incorrect? In case it is incorrect, do you have
> >> >> an idea how should fbdefio be used properly on KMS drivers?
> >> >
> >> > I suppose I was wondering what use fbdefio really has, modern code
> >> > should be using KMS interface and the KMS dirty handling should be
> >> > able to cover those cases.
> >
> > I use fbdefio with the links 2 web browser and with fbi and fbgs image
> > viewers.
> >
> > I tried to look into modifying the links browser to work without fbdefio -
> > but the DRM_IOCTL_MODE_DIRTYFB ioctl requires master mode, which means
> > that it is unuseable by an unprivileged process. If you suggest how should
> > console applications use the framebuffer without fbdefio, I can implement
> > it.
> 
> Well with the console there's really no security. Either you disallow
> touching fbdev, or everyone can read&write whatever they want, even if
> they're not the currently active vt. So security just doesn't exist
> with fbdev.

I added myself to the video group, so that I can open /dev/fb0 and run 
graphics console applications. But I still can't set master mode, so I 
can't issue DRM_IOCTL_MODE_DIRTYFB to update the screen when fbdefio is 
turned off.

> With kms you need logind or someone like that who orchestrates the vt
> switching and makes sure you can read/write other people's stuff.

The Links browser registers two signals via vt_mode.acqsig and 
vt_mode.relsig and repaints the screen or stops painting when they are 
received. If it should do something else - then what?

It would be nice if the kms developers provided a simple graphics console 
application that describes how to use it.

Mikulas