On Sun 16 Aug 23:59 PDT 2015, Alexandre Courbot wrote: > On Thu, Aug 13, 2015 at 10:06 PM, Linus Walleij > <linus.walleij@xxxxxxxxxx> wrote: > > On Tue, Aug 11, 2015 at 12:41 AM, Bjorn Andersson > > <bjorn.andersson@xxxxxxxxxxxxxx> wrote: > > > >> But then the question first goes to Linus & co. > >> > >> gpio_chip->get() can return a negative value to indicate errors (and did > >> so in this case), all parts of the API seems indicates that we can get > >> an error (int vs bool). > > > > Ooops. > > > >> Should we change _gpiod_get_raw_value() to propagate this error? > > > > Yes for now. Can you patch it? :) > > > >> Or > >> should we just ignore this issue and propagate an error as GPIO high > >> reading? > > > > I don't know about the future. In some sense GPIOs are so smallish > > resources that errorhandling every call to read/write them seem to > > be a royal PITA. That is why I wanted to switch them to bool and get > > rid of the problem, but now I also see that maybe that was not such a > > smart idea, if errors do occur on the set/get_value path. > > Nowadays GPIOs may reside at the other end of an i2c bus, which means > that even the simplest operation like reading a GPIO value can > potentially fail. And it will probably not get better - wait until we > implement GPIO-over-IP! :) > Now that's progress! I can't wait ;) > So I'd say it makes sense to propagate errors returned by the driver's > get() hook. This might contradict some of our earlier statements about > simplifying the GPIO API, but is preferrable to having to make a > decision as to which valid value to return if the driver fails... > Sounds good. As we're patching up _gpiod_get_raw_value(), is the lack of a get() implementation the same as a LOW or is that -ENOTSUPP? > It should then be made very clear in the documentation that the only > positive values ever returned by the GPIO API will be 0 and 1 (we > already have a clamping mechanism for that IIRC), and that negative > values are propagated as-is. > That makes sense. I'm however not able to find such clamping macro/mechanism and it would be very beneficial here... > Linus, does that seem reasonable to you? Does anyone has the intention > to address that one or should I add it to my short-term TODO list? If you have some input on above (is lack of get() an error) I can hack up the patch. Regards, Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
