mipi_dbi_typec3_command quirk for 16 bit parallel interfaces

[dsx724]

mipi_dbi_typec3_command setups 8 bpw transfers over SPI

mipi_dbi_spi_transfer(spi, speed_hz, 8, cmd, 1);

Should a quirk or parameter for devices that are behind 16-bit parallel interfaces but communicate over SPI? Or maybe arbitrary bit interfaces?

Otherwise the data gets kind of clobbered. I know these hacked displays are not the primary target of panel-mipi-dbi but it would be good to support with one driver.

[dsx724]

@notro If I code something like reg width handling for this driver and a DT quirk for this, do you think it will get accepted upstream?

[notro]

It's not part of the MIPI DBI specification so it won't be accepted in the panel-mipi-dbi driver.
Your best bet is to add specific support for your panel in a controller driver. Example: drivers/gpu/drm/tiny/ili9486.c

[dsx724]

Most ILI9486 boards uses 16-bit shift registers but not all. I was thinking that maybe we can implement a generic driver for these serial to parallel register displays behind fixed register width. This way we don't clutter the kernel with the same driver under a dozen confusing names due to the bus/register design and create more flexibility.

For example, I have one ILI9486 that is using the SPI interface rather than a SPI to parallel interface via registers. But it can get confusing when people design compatibles.