Den 29.07.2016 10:23, skrev Daniel Vetter:
Actually adding David.
-Daniel
On Fri, Jul 29, 2016 at 10:20:51AM +0200, Daniel Vetter wrote:
On Thu, Jul 28, 2016 at 04:15:04PM +0200, Noralf Trønnes wrote:
This patchset explores the idea of adding a DRM text mode
(like VGA text mode) to get an alternative to fbcon/fbdev.
David Hermann has done alot of work on a fbcon replacement:
- drm: add kernel-log renderer (Mar 2014)[1]
- kmscon:
development started Nov 2011
added to systemd Oct 2014
removed from systemd Jul 2015[2]
Since this work seems to have stalled, I propose an alternative solution
to this problem that will also give VT console support while we're waiting
for a userspace console.
The idea is that the driver provides a modeset like with the fbdev emulation
code, and from this a text buffer representation is made. The console code
can now write to this text buffer and ask for the text buffer to be
flushed/rendered to the pixel buffer.
In this hack/implementation of the idea, I have just hijacked a CMA backed
fbdev framebuffer to keep it simple.
I have reused the default buffer format that VT uses.
Getting panic handling to actually work, seems to be a challenge as Daniel
describes on the DRMJanitors page[3].
Is this idea of a DRM text mode worth developing further?
I guess some simpler drm console with vt support which would allow us to
get rid of fbdev could make sense. And there's definitely going to be a
lot of overlap with a full userspace solution using something like kmscon.
But we can't just add a new drm text console, there's a pile of prep work
needed that David started for either approach:
- Nuking fbdev means no more fbdev drivers for firmware consoles (uboot,
uefi, vga, ...). The simpledrm driver would cover this, would be great
to get that landed (especially now that we have the simple pipe
helpers!).
I have rebased simpledrm on drm_simple_display_pipe and have it working on
a Raspberry Pi. modetest gives me a wrong picture, but that is probably
because of some wrong format conversion since fbdev using the native
rgb565 format works fine.
I could finish this up and send a patch unless David is working on
something?
I have used this version of simpledrm: [PATCH 09/11] drm: add SimpleDRM
driver
https://lists.freedesktop.org/archives/dri-devel/2014-January/052594.html
- One nice benefit of fbdev is that it automatically gets rid of these
firmware-based display drivers when the real driver loads. Some drivers
do this properly even when fbdev isn't enabled (see i915_kick_out_vgacon
and i915_kick_out_firmware_fb), but pretty much all others fail in some
way or the other. David also had some code (iirc as part of simpledrm)
to solve this issue.
- I think we need more than rbg565 render support, iirc David also had
some work in that area.
- None of these approaches has a good answer yet to the configuration
question. For a full VT I think we definitely should share the setup
logic with the fbdev emulation code to make it useful, but as describe
in the DRMJanitors page handlings panics is an entierly different
problem.
Definitely coordinate with David Herrmann here too, since if we do
something in this area it should be widely supported.
Aside: Where's the pull request for your driver? ;-)
I have been working on tinydrm for 6 months straight now and it wasn't fun
anymore. So I figured this was a good time to take a break from it and do
something else for a while :-)
Noralf.
Cheers, Daniel
Noralf.
[1] https://lwn.net/Articles/589858/
[2] https://github.com/systemd/systemd/pull/747
[3] https://www.x.org/wiki/DRMJanitors/#makepanichandlingwork
Noralf Trønnes (3):
drm: Add support for text framebuffer
drm/text: Add panic and boot console support
drm/text: Add VT console support
drivers/gpu/drm/Makefile | 1 +
drivers/gpu/drm/drm-text/Makefile | 5 +
drivers/gpu/drm/drm-text/drm-text-buffer.c | 340 ++++++++++++++++++++++++++++
drivers/gpu/drm/drm-text/drm-text-console.c | 205 +++++++++++++++++
drivers/gpu/drm/drm-text/drm-text-debugfs.c | 295 ++++++++++++++++++++++++
drivers/gpu/drm/drm-text/drm-text-vt.c | 197 ++++++++++++++++
drivers/gpu/drm/drm-text/drm-text.h | 99 ++++++++
7 files changed, 1142 insertions(+)
create mode 100644 drivers/gpu/drm/drm-text/Makefile
create mode 100644 drivers/gpu/drm/drm-text/drm-text-buffer.c
create mode 100644 drivers/gpu/drm/drm-text/drm-text-console.c
create mode 100644 drivers/gpu/drm/drm-text/drm-text-debugfs.c
create mode 100644 drivers/gpu/drm/drm-text/drm-text-vt.c
create mode 100644 drivers/gpu/drm/drm-text/drm-text.h
--
2.8.2
_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/dri-devel
