On Wed, Oct 16, 2024 at 5:47 PM Rob Herring <robh@xxxxxxxxxx> wrote: > On Wed, Oct 16, 2024 at 2:21 AM Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: > > > > This adds the ngpios property to MMIO GPIO. We restrict the > > property to 1..63 since there is no point in 0 GPIO lines and > > we support up to 64bits wide registers for now. > > Why does it need to be restricted? Is something bad going to happen if > for some reason someone tries to control a non-existent GPIO? Unlikely. But the biggest inconvenience is that non-existing GPIO lines gets exposed to userspace which causes confusion. It's a bit like saying you have 32 harddisks on your system just because the register has 32 bits. > If there > is, maybe there should be a specific compatible as the h/w is not so > generic. The gpio-mmio is quite generic, it's the most generic GPIO driver we have. The ngpios property is also generic, it is in: Documentation/devicetree/bindings/gpio/gpio.txt (commit aacaffd1d9a6f8e2c7369d83c21d41c3b53e2edc) At the time (2015) I just documented the already widespread use of this property. It is also reflected in several of the new yaml bindings, a git grep ngpios will show you. Yours, Linus Walleij
