This is board and arch specific and cannot be more generalized than that. > They will have different requirements for pullups, speed, etc. The define > should also start with BOARD_ but some use GPIO_. This is the case > for all PINs including UART, GPIO, SPI, USB, etc... >
I mean after that arch and board-specific config, you end up with a list of general pins available (CS1, CS2, CS3...) which are equivalent to SPI_* in that they're valid everywhere and can be used despite architecture, SPI master or bus number > and the drivers will already have conditionals on those being defined. > Just like SPI_* don't break > > SPI is just a little special because you dont _need_ a CS gpio pin, > but frequently you want it. You need CS pins when you have more than one SPI device in a bus (something very frequent). For example, all this comes from the fact that I'm designing a control system that would benefit from having two CAN busses instead of just one > So you end up with the board specific hooks > for what pin to turn on. > as is here > > https://github.com/apache/incubator-nuttx/blob/cdd111a1faec9b40b707797e00c4afae4956fb3f/boards/arm/stm32/nucleo-f4x1re/src/stm32_spi.c#L140 > > SPI drivers cannot depend on a fixed name for the CS pin because you may > have multiple instances (what I thought you were asking to support) > > It's a fixed name in the sense CS1 is defined in all boards and archs so I can write my driver using SPI_SELECT with CS1 and it will work everywhere > You just update the define in your board.h file to include a mapping for > what > is wired up to pin 5. I cannot do that if I'm not a kernel developer > > When you are bringing up your board one of the first > things you should do is define the pins in your board.h > I'm not bringing up a new board but connecting an *external* supported chip to a supported board via a standard bus > Changing how pins are defined would break everyone so that is unlikely to > change, and it is also not really something that can easily be mapped to > Kconfig. > It doesn't break anything if it's parallel to everything just like SPI_* macros are Grr
