On Thu, Apr 07, 2022 at 10:02:04PM +0200, Javier Martinez Canillas wrote:
The ssd130x driver only provides the core support for these devices but it does not have any bus transport logic. Add a driver to interface over SPI.
There is a difference in the communication protocol when using 4-wire SPI instead of I2C. For the latter, a control byte that contains a D/C# field has to be sent. This field tells the controller whether the data has to be written to the command register or to the graphics display data memory.
But for 4-wire SPI that control byte is not used, instead a real D/C# line must be pulled HIGH for commands data and LOW for graphics display data.
For this reason the standard SPI regmap can't be used and a custom .write bus handler is needed.
Acked-by: Mark Brown broonie@kernel.org