> That's moving the same problem from one place to another instead of > eliminating it: you need to rewrite some part of the driver for each > chip/subchip. No, you wouldn't need that. The device driver will receive a generic GPIO handling interface and it would simply assert/deassert CS line without knowing the specifics of the GPIO impementation on the given architecture. The GPIO interface would be implemented at arch level (and I believe some arch's are already implemented).
During initialization of this device driver lower-half, the GPIO interface instance would be initialized to the correct CS line for this driver instance. Further improvements (minimizing board bringup code to support a driver) could be achieved but with more involved changes. I have some ideas on that (related to my initial attempt at supporting device tree) but I would like to discuss that only when I think I would be able to pursue it. Best, Matias
