On Tue, Jun 04, 2024 at 03:20:31PM +0200, Noralf Trønnes via B4 Relay wrote: > From: Noralf Trønnes <noralf@xxxxxxxxxxx> > > DRM_FORMAT_RGB888 is 24 bits per pixel and it would be natural to send it > on the SPI bus using a 24 bits per word transfer. The problem with this > is that not all SPI controllers support 24 bpw. > > Since DRM_FORMAT_RGB888 is stored in memory as little endian and the SPI > bus is big endian we use 8 bpw to always get the same pixel format on the > bus: b8g8r8. > > The MIPI DCS specification lists the standard commands that can be sent > over the MIPI DBI interface. The set_address_mode (36h) command has one > bit in the parameter that controls RGB/BGR order. This means that the > controller can be configured to receive the pixel as BGR. > > RGB888 is rarely supported on these controllers but RGB666 is very common. > All datasheets I have seen do at least support the pixel format option > where each color is sent as one byte and the 6 MSB's are used. > > All this put together means that we can send each pixel as b8g8r8 and an > RGB666 capable controller sees this as b6x2g6x2r6x2. > > v4: > - s/emulation_format/pixel_format/ (Dmitry) > > Signed-off-by: Noralf Trønnes <noralf@xxxxxxxxxxx> > --- > drivers/gpu/drm/drm_mipi_dbi.c | 29 +++++++++++++++++++++++++---- > include/drm/drm_mipi_dbi.h | 5 +++++ > 2 files changed, 30 insertions(+), 4 deletions(-) > Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> -- With best wishes Dmitry
