Hi Jocelyn. On Tue, Dec 17, 2024 at 3:46 PM Jocelyn Falempe <jfalempe@xxxxxxxxxx> wrote: > On 17/12/2024 15:19, Geert Uytterhoeven wrote: > > On Wed, Dec 4, 2024 at 6:41 PM Jocelyn Falempe <jfalempe@xxxxxxxxxx> wrote: > >> drm_log is a simple logger that uses the drm_client API to print the kmsg boot log on the screen. > >> This is not a full replacement to fbcon, as it will only print the kmsg. > >> It will never handle user input, or a terminal because this is better done in userspace. > >> > >> If you're curious on how it looks like, I've put a small demo here: > >> https://people.redhat.com/jfalempe/drm_log/drm_log_draft_boot_v2.mp4 > >> > >> Design decisions: > >> * It uses the drm_client API, so it should work on all drm drivers from the start. > >> * It doesn't scroll the message, that way it doesn't need to redraw the whole screen for each new message. > >> It also means it doesn't have to keep drawn messages in memory, to redraw them when scrolling. > >> * It uses the new non-blocking console API, so it should work well with PREEMPT_RT > > > > I gave this a try on Koelsch (R-Car M2-W), using rcar-du. > > Unfortunately I don't see any kernel messages, and my monitor complains > > about no signal. Does this require special support from the driver? > > It doesn't require a special support from the driver. But as it is the > first drm client other than fbdev emulation, I'm not surprised it's > broken on some driver. > I know it works on virtio-gpu, nouveau, amdgpu, and even on a OnePlus 6 > (Qualcomm SDM845/freedreno), without requiring driver changes. > > Do you have a serial console on this device, to check if there is > something in kmsg? Nothing interesting to see. Compared to the fbdev client: rcar-du feb00000.display: [drm] Registered 2 planes with drm panic [drm] Initialized rcar-du 1.0.0 for feb00000.display on minor 0 rcar-du feb00000.display: [drm] Device feb00000.display probed -Console: switching to colour frame buffer device 240x67 -rcar-du feb00000.display: [drm] fb0: rcar-dudrmfb frame buffer device I did verify (by adding my own debug prints) that the code does get to the success case in drm_log_register(). Thanks! Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
