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?
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