Hi! I replaced DRM_FBDEV_EMULATION with DRM_CLIENT_LOG (DRM_CLIENT_DEFAULT="log") on a kernel with DRM_PANIC enabled, using kmscon as the userspace terminal. Nothing initialises the display after the native driver loads.
The result is a blank screen, no output at all from boot. DRM_CLIENT_LOG (boot logs don't show up at all) and DRM_PANIC (forced a panic to try this out) also don't work, since neither can render without an initialised display. This can be verified by checking "/sys/class/drm/card0-*/status" (all outputs show "unknown") and "/sys/class/drm/card0-*/modes" (empty) after boot. Writing "detect" to "/sys/class/drm/card0-HDMI-A-1/status" (or any output for that matter) resolves the issue, the connector is probed, modes are populated, and kmscon can be started correctly. This suggests DRM_FBDEV_EMULATION previously triggered some display initialisation/probing during boot that is not happening with DRM_CLIENT_LOG. I can't say if SIMPLEDRM (and SIMPLEFB) are affected, the result in my system is a immediate blank screen and no signal, I don't know if its because the main graphics driver initialise very quickly during boot or if SIMPLEDRM is also affected. Hardware: AMD RX 6600 XT (Navi23/AMDGPU), although I believe this affects any driver. Kernel version: 7.0.11-gentoo Config diff: 2849a2850 > # CONFIG_VGA_SWITCHEROO is not set 2874,2879c2875,2878 < CONFIG_DRM_FBDEV_EMULATION=y < CONFIG_DRM_FBDEV_OVERALLOC=100 < # CONFIG_DRM_FBDEV_LEAK_PHYS_SMEM is not set < # CONFIG_DRM_CLIENT_LOG is not set < CONFIG_DRM_CLIENT_DEFAULT_FBDEV=y < CONFIG_DRM_CLIENT_DEFAULT="fbdev" --- > # CONFIG_DRM_FBDEV_EMULATION is not set > CONFIG_DRM_CLIENT_LOG=y > CONFIG_DRM_CLIENT_DEFAULT_LOG=y > CONFIG_DRM_CLIENT_DEFAULT="log" 2978,2986d2976 < CONFIG_FB_CORE=y < # CONFIG_FB_DEVICE is not set < CONFIG_FB_SYS_FILLRECT=y < CONFIG_FB_SYS_COPYAREA=y < CONFIG_FB_SYS_IMAGEBLIT=y < CONFIG_FB_SYSMEM_FOPS=y < CONFIG_FB_DEFERRED_IO=y < CONFIG_FB_SYSMEM_HELPERS=y < CONFIG_FB_SYSMEM_HELPERS_DEFERRED=y 3021,3024d3010 < CONFIG_FRAMEBUFFER_CONSOLE=y < # CONFIG_FRAMEBUFFER_CONSOLE_LEGACY_ACCELERATION is not set < CONFIG_FRAMEBUFFER_CONSOLE_DETECT_PRIMARY=y < # CONFIG_FRAMEBUFFER_CONSOLE_ROTATION is not set 3027d3012 < # CONFIG_LOGO is not set 4473d4457 < # CONFIG_FONT_SUN8x16 is not set Guilherme B.
