As I see it, CONFIG_AT91 would mean that you have a a certain class of peripherals which is developed for the AT91 range of processors (and is used by the AVR32 as well) The name is probably slightly misleading, but convenient.
Not having this definition, will soon mean that you have statements like the following:
#if defined(CONFIG_AT91RM9200) || \ defined(CONFIG_AT91SAM9260) || \ defined(CONFIG_AT91SAM9261) || \ defined(CONFIG_AT91SAM9263) || \ defined(CONFIG_AT91SAM9G10) || \ defined(CONFIG_AT91SAM9G15) || \ defined(CONFIG_AT91SAM9G20) || \ defined(CONFIG_AT91SAM9G41) || \ defined(CONFIG_AT91SAM9M10) || \ defined(CONFIG_AT91SAM9M11) || \ defined(CONFIG_AT91CAP9) || \ defined(CONFIG_AT572D940)
This statement will have to be updated every time a new MCU is released.
Having the statment #if defined(CONFIG_AT91)
should definitely reduce the maintenance of drivers.
I fully agree with Ulf, we need to have a better CONFIG, but I'm not sure that CONFIG_AT91 is the right one
We have actually in the tree the following CPU CONFIG_AT91CAP9 CONFIG_AT91RM9200 CONFIG_AT91SAM9260 CONFIG_AT91SAM9261 CONFIG_AT91SAM9263 CONFIG_AT91SAM9RL
and as mention Ulf are going to have more and more
maybe we can use config related to the functionnality or the sub-class CPU ex : CONFIG_MACB_INCLK
Best Regards, J.