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. 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 -- 2.41.0
