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On 23/12/2021 11:00, Thomas Zimmermann wrote:
tl;dr: Enable DRM for all graphics output and retire fbdev drivers in TW.
Hi!
For quit a few releases, Linux' DRM stack has been able to provide display output from the early boot stages on. Next year, we want to modernize Tumbleweed's graphics stack and use DRM for all graphics output.
To get graphics output during the early stages of booting, Linux still uses fbdev infrastructure and a few HW-independed drivers, such as efifb and vesafb.
This functionality is now available in DRM as well. We will switch early-boot graphics from fbdev to DRM and retire the related fbdev drivers. Fbdev userspace interfaces (i.e., /dev/fb0) will still be available via the new driver.
The change has no effect on graphics output of the fully booted machine. Just as now, at some point during boot, a hardware-specific driver, such as amdgpu, i915, etc., will take over the display.
Why switch? The generic DRM driver provides a fallback for all systems without hardware-specific drivers. Even with broken hardware drivers, generic DRM can most likely boot and provide graphics output. This isn't easily possible with fbdev. Fbdev has been out of date for several years. Modern graphics userspace slowly uses the ability to run on top of fbdev. Most notably, wayland compositors are affected by this. We also have received reports about systems being unable to boot because of fbdev.
TW's X11 and userspace should be ready (sans bugs). If you want to test, Takashi provides a kernel that has full-DRM enabled at
https://download.opensuse.org/repositories/home:/tiwai:/simpledrm/
If you install and boot the kernel, you should ideally see no difference. Once booted the hardware's driver will do the graphics output. To test if you booted with generic DRM, do
dmesg | grep drm
on the command line. The output should mention 'simpledrm' somewhere. If you want to run your system with the generic driver only, pass
nomodeset
on the kernel command line in Grub. The booted system should run with only software rendering, but provide useful output via X11, wayland and console.
We welcome bug reports. If you find issues, please leave a comment in boo#1193250
https://bugzilla.opensuse.org/show_bug.cgi?id=1193250
Best regards Thomas I just wonder what this implies for text based output only? Another consequence is that the kernel footprint will be raised again due to the presence of the DRM code. In graphics mode, this is no issue (the footprint remains more or less the same) but in text mode it requires code availability which was not needed before.
Regards, Frans.