Hi Am 20.04.21 um 10:46 schrieb Daniel Vetter: > On Mon, Apr 19, 2021 at 10:00:56AM +0200, Geert Uytterhoeven wrote: >> Hi Thomas, >> >> On Fri, Apr 16, 2021 at 11:00 AM Thomas Zimmermann wrote: >>> This patchset adds support for simple-framebuffer platform devices and >>> a handover mechanism for native drivers to take-over control of the >>> hardware. >>> >>> The new driver, called simpledrm, binds to a simple-frambuffer platform >>> device. The kernel's boot code creates such devices for firmware-provided >>> framebuffers, such as EFI-GOP or VESA. Typically the BIOS, UEFI or boot >>> loader sets up the framebuffers. Description via device tree is also an >>> option. >> >> I guess this can be used as a replacement for offb, too... >> >>> Patches 4 to 8 add the simpledrm driver. It's build on simple DRM helpers >>> and SHMEM. It supports 16-bit, 24-bit and 32-bit RGB framebuffers. During >> >> .... if support for 8-bit frame buffers would be added? Offb doesn't seem to be tied to the simple-framebuffer support. So adding a new driver or extending the simple-framebuffer code would be required. Not a big deal, though. Patch 3 of this patchset adds the ability to create generic drivers within DRM. > > Is that 8-bit greyscale or 8-bit indexed with 256 entry palette? Former > shouldn't be a big thing, but the latter is only really supported by the > overall drm ecosystem in theory. Most userspace assumes that xrgb8888 > works, and we keep that illusion up by emulating it in kernel for hw which > just doesn't support it. But reformatting xrgb8888 to c8 is tricky at > best. The uapis are all there for setting the palette, and C8 is a defined > format even with atomic kms interface, but really there's not much > userspace for it. In other words, it would work as well as current offb > would, but that's at least that. I think we can just use a shadow palette in the drm driver: If the drm framebuffer is in C8, use the userspace's palette. If the drm framebuffer is in XRGB, use a palette that represents RGB332. The driver would do on-the-fly conversion; just like cirrus does. Best regards Thomas > -Daniel > -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Felix Imendörffer