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 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. Yours, Linus Walleij
