On 06/23/2016 12:04 PM, Linus Walleij wrote: > 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/* Hm. May be i misunderstood samthing (and sry, if my following question is dummy as I've not followed closely new GPIO ABI development), but.. - from above description it seems that global numbering system is not really solved :( instead it's been moved one level up and now the same happens with gpiocipX devices :( Wouldn't it be reasonable to add possibility to create named/labeled gpiocipX devices from the very beginning, like: "/dev/gpiocipX[_name|label], or "/dev/gpiocip[_name|label]", or .. Actually, struct gpio_chip has label field already. PS. From my experience, the worst case with dev numbering usually happens after few insmod/rmmod (or sometimes after suspend/resume) iterations - ttyX ;..(. > > 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. > -- regards, -grygorii -- 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
