On Wed, Dec 17, 2014 at 11:44 AM, Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > On Wed, Dec 17, 2014 at 11:45:01AM +0900, Alexandre Courbot wrote: >> Actually we are not that far from being able to do completely without >> any GPIO number, and maybe that's what we should aim for. I think the >> only remaining offender is the sysfs interface. > > And that is a user API, and there's lots of users of it (eg, on Raspberry > Pi platforms.) So changing it isn't going to be easy - I'd say that it's > impractical. > > What you're suggesting would be like re-numbering Linux syscalls. The problem is that right now if we set the .base of a gpio_chip to -1 for dynamic allocation of GPIO numbers and we have more than one GPIO chip in the system, the numbers basically depend on probe order, and may theoretically even differ between two boots. So in these cases preserving the ABI means preserving the unpredictability of these assigned numbers or something. For the old usecases with a single GPIO controller and a fixed base offset of e.g. 0 (which I suspect was implicit in the initial design of the subsystem) things work fine as always, it's these new dynamic use cases that destabilize the ABI. Yours, Linus Walleij -- 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
