On Fri, Dec 02, 2022 at 06:06:01PM +0200, Tomi Valkeinen wrote: > On 02/12/2022 17:56, Geert Uytterhoeven wrote: > > On Fri, Dec 2, 2022 at 4:32 PM Tomi Valkeinen wrote: > >> On 02/12/2022 15:16, Tomi Valkeinen wrote: > >>> These kms++ patches add support for Y210 format. > >>> > >>> I didn't find a super clear description of the byte order for Y210 > >>> anywhere. If someone knows what it is supposed to be, I'd appreciate > >>> verifying the code =). > >> > >> Actually, this: > >> > >> https://learn.microsoft.com/en-us/windows/win32/medfound/10-bit-and-16-bit-yuv-video-formats#overview > >> > >> indicates that the 10-bit values should be shifted by 6. So the drawing > >> code in this series is probably not right. > > > > https://elixir.bootlin.com/linux/latest/source/include/uapi/drm/drm_fourcc.h#L212 > > seems to confirm that? > > Hmm, indeed. I've looked at that before but I couldn't decipher it, but > now the text makes sense. Although afaics, it doesn't say that each > component is a 16-bit little endian. And I don't get the "little endian > per 2 Y pixels". > > So if I get this right... > > The first byte in memory is the two lowest bits of Y0 in bits 6 and 7. > The rest of the first byte is zero padding. > > The second byte is the 8 highest bits of Y0. > > Then following the same method, Cb, Y1, Cr. I would have said in bits 7 and 6 for the first byte, but I assume we mean the same. Apart from that, your interpretation is the same as mind. However, if your aim is to support the 10bpp YUV 4:2:2 format of the VSP, I'm not sure this is correct. Assuming you plan to set F2B=1 to align bits towards the MSB, it's not clear if the endianness can be configured. The four permutations of the packed YUYV components are achievable as far as I can tell (see figure 60.12 in the documentation), but I didn't immediately find a place where the endianness of each 16-bit value could be configured. Figure 60.15 mentions "example in case of big endian", I don't know if it's an example, or the only possible option. You may want to try both. -- Regards, Laurent Pinchart
