On Sun, Jun 19, 2016 at 03:08:23AM +0200, Uwe Kleine-König wrote: > Hello Linus, > > On Sat, Jun 18, 2016 at 10:25:45AM +0200, Linus Walleij wrote: > > On Wed, Jun 15, 2016 at 9:24 AM, Uwe Kleine-König > > <u.kleine-koenig@xxxxxxxxxxxxxx> wrote: > > > On Wed, Jun 15, 2016 at 08:56:58AM +0200, Linus Walleij wrote: > > > > >> The GPIO numbering scheme is a matter of Linux internals and > > >> not about hardware description IMO. > > > > > > Not sure if I should agree here or not. It's very usual that the > > > "internal" gpio numbers match the hardware reference manual. I know this > > > from imx, at91, all pre-dt platforms, I'm sure there are more, and I bet > > > I'm not the only one relying on this for omap. > > > > I think it will still match nicely against the chip-local offsets of the > > primary gpiochip so it'll be fine with a chardev too. The same was/is > > I cannot follow. What is the primary gpiochip? The first one? What is a > "chip-local offset". Just 3 for the fourth gpio of a given gpio bank? > I guess the problem is that I didn't follow development of the gpio > chardev. If I've understood correctly, Linus was on about the id space for GPIOs under a particular gpiochip. If I've understand correctly, you're trying to ensure consistent numbering the the *global* ID space shared by all GPIO chips present in a system? > > the case of the first interrupts on x86 I think, but with the plethora of > > irqchips and dependency on probe order etc the assumption is > > nowadays to dangerous. > > > > > And this is very usual in the dt world, too: > > > > > > $ git grep -El 'gpio. = \&gpio' arch/arm/boot/dts | wc -l > > > 37 > > > > Aha I didn't even know. Well I guess I could allow it for OMAP too > > then, but I want an ACK from one of the DT binding maintainers. 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. Thanks, Mark. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
