Julius Werner <jwerner@xxxxxxxxxxxx> writes: Hello Julius, >> On Coreboot platforms, a system framebuffer may be provided to the Linux >> kernel by filling a LB_TAG_FRAMEBUFFER entry in the Coreboot table. But >> it seems SeaBIOS payload can also provide a VGA mode in the boot params. >> >> [...] >> >> To prevent the issue, make the framebuffer_core driver to disable sysfb >> if there is system framebuffer data in the Coreboot table. That way only >> this driver will register a device and sysfb would not attempt to do it >> (or remove its registered device if was already executed before). > > I wonder if the priority should be the other way around? coreboot's > framebuffer is generally only valid when coreboot exits to the payload > (e.g. SeaBIOS). Only if the payload doesn't touch the display > controller or if there is no payload and coreboot directly hands off > to a kernel does the kernel driver for LB_TAG_FRAMEBUFFER make sense. > But if there is some other framebuffer information passed to the > kernel from a firmware component running after coreboot, most likely > that one is more up to date and the framebuffer described by the > coreboot table doesn't work anymore (because the payload usually > doesn't modify the coreboot tables again, even if it changes hardware > state). So if there are two drivers fighting over which firmware > framebuffer description is the correct one, the coreboot driver should > probably give way. > That's a very good point. I'm actually not familiar with Coreboot and I used an educated guess (in the case of DT for example, that's the main source of truth and I didn't know if a Core table was in a similar vein). Maybe something like the following (untested) patch then?
