Re: [RFC] Deprecation and removal of the drm2 driver

On Fri, May 18, 2018 at 09:33:40PM +0100, Johannes Lundberg wrote:
> On Fri, May 18, 2018 at 9:22 PM, Ben Widawsky <ben_at_bwidawsk.net> wrote:
> 
> > On 18-05-18 14:15:03, Warner Losh wrote:
> > > On Fri, May 18, 2018 at 2:12 PM, Johannes Lundberg <johalun0_at_gmail.com>
> > > wrote:
> > >
> > > >
> > > >
> > > > On Fri, May 18, 2018 at 9:03 PM, Warner Losh <imp_at_bsdimp.com> wrote:
> > > >
> > > >> On Fri, May 18, 2018 at 1:30 PM, Steve Kargl <
> > > >> sgk_at_troutmask.apl.washington.edu> wrote:
> > > >>
> > > >> > On Fri, May 18, 2018 at 09:14:24PM +0200, Andreas Nilsson wrote:
> > > >> > > On Fri, May 18, 2018, 20:00 Niclas Zeising <zeising_at_freebsd.org>
> > > >> wrote:
> > > >> > >
> > > >> > > > I propose that we remove the old drm2 driver (sys/dev/drm2) from
> > > >> > > > FreeBSD.  I suggest the driver is marked as deprecated in 11.x
> > and
> > > >> > > > removed from 12.0, as was done for other drivers recently.  Some
> > > >> > > > background and rationale:
> > > >> > > >
> > > >> > > > The drm2 driver was the original port of a KMS driver to
> > FreeBSD.
> > > >> It
> > > >> > > > was done by Konstantin Belousov to support Intel graphics
> > cards, and
> > > >> > > > later extended by Jean-S??bastien P??dron as well as Konstantin to
> > > >> match
> > > >> > > > what's in Linux 3.8.  This included unstable support from
> > Haswell,
> > > >> but
> > > >> > > > nothing newer than that.
> > > >> > > >
> > > >> > > > For quite some time now we have had the
> > graphics/drm-stable-kmod and
> > > >> > > > graphics/drm-next-kmods which provides support for modern AMD
> > and
> > > >> Intel
> > > >> > > > graphics cards.  These ports, together with the linuxkpi, or
> > lkpi,
> > > >> has
> > > >> > > > made it significantly easier to port and update our graphics
> > > >> drivers.
> > > >> > > > Further, these new drivers cover the same drivers as the old
> > drm2
> > > >> > driver.
> > > >> > > >
> > > >> > > > What does the community think?  Is there anyone still using the
> > drm2
> > > >> > > > driver on 12-CURRENT?  If so, what is preventing you from
> > switching
> > > >> to
> > > >> > > > the port?
> > > >> > > >
> > > >> > > > Thank you
> > > >> > > > Regards
> > > >> > > > --
> > > >> > > > Niclas Zeising
> > > >> > > > FreeBSD x11/graphics team
> > > >> > > > _______________________________________________
> > > >> > > > freebsd-current_at_freebsd.org mailing list
> > > >> > > > https://lists.freebsd.org/mailman/listinfo/freebsd-current
> > > >> > > > To unsubscribe, send any mail to "freebsd-current-unsubscribe_at_
> > > >> > freebsd.org"
> > > >> > > >
> > > >> > >
> > > >> > > Sounds good ( deprecate resp remove ). It causes more confusion
> > and
> > > >> > > problems and it solves nothing.
> > > >> > >
> > > >> >
> > > >> > Check the Makefiles
> > > >> >
> > > >> > % more /usr/ports/graphics/drm-next-kmod/Makefile
> > > >> >
> > > >> > ONLY_FOR_ARCHS= amd64
> > > >> > ONLY_FOR_ARCHS_REASON=  the new KMS components are only supported on
> > > >> amd64
> > > >> >
> > > >> > Not to ia32 friendly.
> > > >> >
> > > >>
> > > >> So do people use i386 for desktop? And need the latest KMS stuff?
> > > >>
> > > >
> > > > Yeah I was wondering the same.. If you're running i386, do you need drm
> > > > drivers? Will scfb work an i386? (probably has legacy bios and if I
> > > > remember correctly, scfb is UEFI only)
> > > > I do feel sorry for anyone who would have to revert back to VESA...
> > > >
> > > > Would it be too much trouble to move it to a port?
> > > >
> > >
> > > If there's someone who needs it for i386, and wants to do the work and
> > > maintain it, we should allow it. But the drm2 maintainers have said its
> > > likely totally broken anyway.
> > >
> > > Warner
> >
> > As a long time developer in drm/i915, and newly interested in FreeBSD (ie.
> > no
> > history on the matter), is there some upside and/or desire to have native
> > support, or is the drm-next-kmod solution good enough?
> >
> 
> Given the fast evolution of graphics hardware and the amount of code in
> only the AMD and Intel drivers, keep several native implementations seems
> impossible, if not wasteful.
> If you are referring to drm2 in the kernel, that's not much more native
> than the drm kmods, it still uses a linux compatibility layer (but not as
> sophisticated).
Drm2 does not use linux compat layer.

drm2 is probably better on older chipsets which use AGP emulation, i.e.
everything up to SandyBridge-1. Does drm-next run on gen3 and gen4 at
all ? In particular, I did obtained real bug reports from people running
gen 3 hardware. E.g. you cannot run amd64 kernel on T60, but you can run
i386 and get hw support with drm2.

I still have GM45 (gen4) laptop and use it daily with the drm from the
tree. I effectively dropped supporting it when half of the HSW support
code were imported.

> 
> If we were to focus our effort somewhere, it should be to create a Common
> Kernel Programming Interface for Linux and *BSDs, especially for DRM
> drivers. Something a bit more stable that what we see in Linux today.