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 with simpledrm and mgag200, using a new get_scanout_buffer() api 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) v3: * Rework the drawing functions, to write the pixels line by line and to use the drm conversion helper to support other formats. (Thomas Zimmermann) v4: * Fully support all simpledrm formats using drm conversion helpers * Rename dpanic_* to drm_panic_*, and have more coherent function name. (Thomas Zimmermann) * Use drm_fb_r1_to_32bit for fonts (Thomas Zimmermann) * Remove the default y to DRM_PANIC config option (Thomas Zimmermann) * Add foreground/background color config option * Fix the bottom lines not painted if the framebuffer height is not a multiple of the font height. * Automatically register the driver to drm_panic, if the function get_scanout_buffer() exists. (Thomas Zimmermann) * Add mgag200 support. With mgag200 support, I was able to test that the xrgb8888 to rgb565 conversion is working. 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 (4): drm/format-helper: Export line conversion helper for drm_panic drm/panic: Add a drm panic handler drm/simpledrm: Add drm_panic support drm/mgag200: Add drm_panic support drivers/gpu/drm/Kconfig | 22 ++ drivers/gpu/drm/Makefile | 1 + drivers/gpu/drm/drm_drv.c | 8 + drivers/gpu/drm/drm_format_helper.c | 88 +++++- drivers/gpu/drm/drm_panic.c | 413 ++++++++++++++++++++++++++ drivers/gpu/drm/mgag200/mgag200_drv.c | 24 ++ drivers/gpu/drm/tiny/simpledrm.c | 15 + include/drm/drm_drv.h | 14 + include/drm/drm_format_helper.h | 9 + include/drm/drm_panic.h | 41 +++ 10 files changed, 627 insertions(+), 8 deletions(-) create mode 100644 drivers/gpu/drm/drm_panic.c create mode 100644 include/drm/drm_panic.h base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c -- 2.41.0
