On Wed, Jun 22, 2016 at 6:16 PM, Mark Rutland <mark.rutland@xxxxxxx> wrote: > In general, our use of aliases is rather ill-defined. It would be nicer > if we could address devices in a similar manner to disks or partitions, > e.g. by path or uuid, but I don't think we have anything sensible we can > use there. > > Given that, I can see the use of an alias to provide a consistent way of > referring to a particular gpiochip (and maybe we need to expose the > alises information somehow to userspace), but IMO that's independent of > any global ID space, probe ordering, etc. >From the kernel point of view the way forward to identify and refer to a particular gpiochip is using /dev/gpiochipN the character device. If complete topology of the bus placement etc is needed, userspace can traverse /sys/bus/gpio/* This solves the big problem with the current global numbering system in /sys/class/gpio/* So what this alias should address would be two things: - Solve the immediate issue of the global number space for the legacy sysfs ABI, but also: - Determine which chip is gpiochip0, gpiochip1, .. etc in the new ABI, so the devices get consistent numbering. The latter is lightly frowned upon by the udev people: they think it is more proper to traverse /sys to get topological information about the devices. I would appreciate if a patch to add alias handling would take care of both these things if we apply it. Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
