On Wednesday, August 9, 2023 3:17:27 PM EDT 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 the drm_client API. > This implementation with the drm client API, allocates new framebuffers, and looks a bit too complex to run in a panic handler. > Maybe we should add an API to "steal" the current framebuffer instead, because in a panic handler user-space is already stopped. > > To test it, make sure you're using the simpledrm driver, and trigger a panic: > echo c > /proc/sysrq-trigger > > There is one thing I don't know how to do, is to unregister the drm_panic when the graphic driver is unloaded. > drm_client_register() says it will automatically unregister on driver unload. But then I don't know how to remove it from my linked list, and free the drm_client_dev struct. > > This is a first draft, so let me know what do you think about it. Hi, Oh wow, that's my post. I'm sorry about the late reply, I only saw this late yesterday, and I wanted to test it first. I had to edit my test QEMU script a bit to use TianoCore for virtual UEFI boot as there is no gfxmode=keep for SimpleDRM to work otherwise when specifying -kernel to qemu AFAIK I tested it, and it works! That's pretty cool, although is it possible to show the message, such as "attempted to kill init"? I like the little ASCII Tux. Maybe an ASCII /!\ or [X] on the belly would make it more obvious to users that it is an error condition. Especially for non-English speaking users I will tweak my script a bit so I can test it more quickly in the future too. Thanks! > > 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 | 286 +++++++++++++++++++++++++++++++ > drivers/gpu/drm/tiny/simpledrm.c | 2 + > include/drm/drm_panic.h | 26 +++ > 6 files changed, 329 insertions(+) > create mode 100644 drivers/gpu/drm/drm_panic.c > create mode 100644 include/drm/drm_panic.h > > > base-commit: 6995e2de6891c724bfeb2db33d7b87775f913ad1 >
