On Tue, Dec 08, 2020 at 01:41:52PM +0100, Linus Walleij wrote: > On Tue, Dec 8, 2020 at 10:57 AM Johan Hovold <johan@xxxxxxxxxx> wrote: > > [Me] > > > > A better approach might be to create an array of names > > > prepended with something device-unique like the USB > > > bus topology? Or do we need a helper to help naming the > > > GPIOs? What would be helpful here? > > > > > > name = kasprintf(GFP_KERNEL, "%s-NAME", topology_str); > > > > Well we started discussing this back when we only had the sysfs > > interface which suffered from the same problem. I thought the chardev > > interface was supposed to get rid of the assumption of a flat name > > space? Perhaps in v3 of the ABI. ;P > > It's "mostly true" that the line names are unique per-chip actually, > because people don't like the nasty warning message. I wonder > if anything would really break if I go in and make a patch to > enforce it, since all drivers passing ->names in the gpiochip > are in the kernel we can check them all. > > If the names are unique-per-chip, we can add a restriction like this > with the requirement: > > depends on !GPIO_SYSFS > This sounds reasonable to me. > so it can't even be compiled in if someone is using the sysfs. > > That should solve the situation where people are (ab)using > the sysfs and getting name collisions as a result. > > Then it should be fine for any driver to provide a names array > provided all the names are unique on that gpiochip. > > I doubt it would break anything, but let's see what Geert says. > He has some special usecases in the gpio-aggregator driver > which will incidentally look for just linenames when > aggregating gpios, but I feel it is a bit thick for it to work > with multiple hot-pluggable GPIO chips as well, I don't think > that is its usecase. (We all want to be perfect but...) > > > But what about any other non-pluggable > > IC, which provides a few named GPIO lines and of which there could be > > more than one in a system? > > I think if there are such, and the lines are unique per-chip > we should make the drivers depend on !GPIO_SYSFS. > > > The topology is already encoded in sysfs and it seems backwards to have > > each and every gpio driver reconstruct it. > > I agree. > > I think if this driver already has unique line-names per-gpiochip > we could actually make it depend on !GPIO_SYSFS and > just add the names. > Sure thing. Johan, if you are okay with this I can resubmit incorporating Linus's suggestion. Thanks, Mani > Yours, > Linus Walleij
