On 19/09/2023 01:19, Noralf Trønnes wrote:
Hi,
On 9/15/23 10:28, Jocelyn Falempe wrote:
This introduces a new drm panic handler, which displays a message when a panic occurs.
So when fbcon is disabled, you can still see a kernel panic.
This is one of the missing feature, when disabling VT/fbcon in the kernel:
https://www.reddit.com/r/linux/comments/10eccv9/config_vtn_in_2023/
Fbcon can be replaced by a userspace kms console, but the panic screen must be done in the kernel.
This is a proof of concept, and works only with simpledrm, using a new get_scanout_buffer() api
There's a panic handling entry in Documentation/gpu/todo.rst pointing to
some work done in this area.
Thanks a lot for this pointer, I wasn't aware of this previous drm panic
attempt. I hope this one will go a bit further ;)
Also I wasn't sure about what is allowed or not in the panic handler,
and this doc makes things really clear.
Regarding the fbcon interactions, I prevent this at build time, I rely
on userspace consoles, and hope they will progressively replace fbcon.
My real question is how did I missed that ? My google-fu failed me this
time.
Best regards,
--
Jocelyn
Noralf.
To test it, make sure you're using the simpledrm driver, and trigger a panic:
echo c > /proc/sysrq-trigger
v2
* Use get_scanout_buffer() instead of the drm client API. (Thomas Zimmermann)
* Add the panic reason to the panic message (Nerdopolis)
* Add an exclamation mark (Nerdopolis)
I didn't reuse the fbdev functions yet, that would need some fbdev refactoring, because they rely on struct fb_info, and struct vc_data (for font/console). But I still plan to at least try it for v3.
A few more though:
1) what about gpu with multiple monitor connected ?
maybe get_scanout_buffer() could return a list of scanout buffers ?
2) I think for some GPU drivers, there might need a flush_scanout_buffer() function, that should be called after the scanout buffer has been filled ?
Best regards,
Jocelyn Falempe (2):
drm/panic: Add a drm panic handler
drm/simpledrm: Add drm_panic support
drivers/gpu/drm/Kconfig | 11 ++
drivers/gpu/drm/Makefile | 1 +
drivers/gpu/drm/drm_drv.c | 3 +
drivers/gpu/drm/drm_panic.c | 270 +++++++++++++++++++++++++++++++
drivers/gpu/drm/tiny/simpledrm.c | 17 ++
include/drm/drm_drv.h | 14 ++
include/drm/drm_panic.h | 41 +++++
7 files changed, 357 insertions(+)
create mode 100644 drivers/gpu/drm/drm_panic.c
create mode 100644 include/drm/drm_panic.h
base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c
