On Sun, Dec 23, 2007 at 03:47:50AM +0100, Segher Boessenkool wrote: > > OF device tree GPIOs bindings are similar to IRQs: > > But GPIOs are a very different thing. Most importantly, the "number" > of a GPIO is completely local to the GPIO controller.
Yes... just as interrupt specifiers are local to their interrupt domain. > > pario0: [EMAIL PROTECTED] { > > #gpio-cells = <2>; > > Your Linux code doesn't actually use this. Why is it needed, anyway? > You should be able to encode a GPIO identifier in a single 32-bit word, > for any possible GPIO controller. > > > num-ports = <7>; > > What is this? What is a "port"? This doesn't belong in a generic GPIO > binding. > > > [EMAIL PROTECTED] { > > gpios = <bank pin bank pin bank pin>; > > gpio-parent = <&pario0>; > > Not every GPIO controller has banks. That's just bad terminology in the example. "bank pin" means an arbitrary format gpio specifier. > Not every device uses GPIOs > on a single GPIO controller. It is inconvenient to force all bindings > to use the same name ("gpios") for its property that shows the GPIOs > (and for it to have only one such property). > > So I recommend: > > -- Advise (in the generic GPIO binding) people to use > < phandle-of-gpio-controller gpio-id-on-that-controller > > to refer to a GPIO from some device node; Ah, yes, that's a good point. Given the ugly workarounds we need to deal with devices which have interrupts from multiple domains, we don't want to copy that limitation to the GPIO scheme. > -- And either: > -- Define (in the generic GPIO binding) that a "gpio-id" is a single > 32-bit cell; > or > -- Define (in the generic GPIO binding) that a "gpio-id" is a number > of 32-bit cells, and that that number of cells is encoded as a > 32-bit > integer in the "#gpio-cells" property in the device node of the > respective GPIO controller. This option was the idea; the "bank pin" information has a format local to the gpio controller. I agree the terminology needs to change to "gpio specifier" by analogy with the interrupt tree, though. > (I like the first option better, unless someone can think of some > reasonable > situation where some specific GPIO controller binding needs more than > 32 bits > to encode GPIO #). I can't think of a situation where it would be strictly speaking necessary, but I can think of several where it would be more convenient. GPIO controllers that do have a bank/pin arrangement is one. GPIO controllers than have a pin number, plus some sort of direction or level information is another. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev