Benjamin Herrenschmidt schrieb: > On Tue, 2008-02-19 at 00:35 +0100, Clemens Koller wrote: >> [EMAIL PROTECTED] schrieb: >>> On Mon, 18 Feb 2008 08:18:47 +0100, Krzysztof Helt said: >>>> I know two fb drivers which use endianess information (pm2fb and >>>> s3c2410fb). >>>> Both resolve endianess at driver level. Actually, both handle it by >>>> setting special >>>> bits so the graphics chip itself reorder bytes to transform foreign >>>> endianess. >>>> I understand that this patch is for chips which cannot reorder bytes by >>>> themselves. >>> Does anybody know of such a chip that's actually available in the wild? Or >>> are >>> we writing drivers for speculative possible chips? >>> >> I had troubles with the Silicon Motion SM501/SM502 endianess on PowerPC PCI >> vs. LocalBus. >> The chip also has a register to swap endianess, but that seems to only >> affect some >> LocalBus modes. >> The current fb and X drivers are working, but when it comes to font >> aliasing and hw-acceleration, the problems start to rise again... > > Most "sane" gfx chips nowadays provide configurable surfaces that allow > to perform the swap when writing/reading from regions of the > framebuffer, with the ability to set a different swapper setting (based > on bit depth) per region.
Most! But not the SM50x. I still hope I would be wrong here. :-( > Then there is also the risk that your PCI<->Localbus has been wired > improperly :-) That's not an issue in my case. The SM50x can be connected to either an PCI or some Local/CPU-whateverbus IF. I.e. on the MPC85xx PowerPC, PCI and LocalBus are separate bussses. If the sm501 is attached to the MPC85xx' PCI like any other video card, the PCI config-space is can be accessed as usual, whereas the framebuffer memory area is byte-swapped compared to other common video cards. So, to get back on topic: I would welcome endianess swapping in SW. Some architectures (PowerPC) should also be able to do swapped-endian mmapping. I just haven't had time for a closer look but it looks also interesting way to do it that way. Regards, Clemens _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
