On 04/16/2013 05:14 PM, Jon Hunter wrote: > > On 04/16/2013 05:11 PM, Stephen Warren wrote: >> On 04/16/2013 01:27 PM, Jon Hunter wrote: >>> >>> On 04/16/2013 01:40 PM, Stephen Warren wrote: >>>> On 04/15/2013 05:04 PM, Jon Hunter wrote: >> ... >>>>> If some driver is calling gpio_request() directly, then they will most >>>>> likely just call gpio_to_irq() when requesting the interrupt and so the >>>>> xlate function would not be called in this case (mmc drivers are a good >>>>> example). So I don't see that as being a problem. In fact that's the >>>>> benefit of this approach as AFAICT it solves this problem. >>>> >>>> Oh. That assumption seems very fragile. What about drivers that actually >>>> do have platform data (or DT bindings) that provide both the IRQ and >>>> GPIO IDs, and hence don't use gpio_to_irq()? That's entirely possible. >>> >>> Right. In the DT case though, if someone does provide the IRQ and GPIO >>> IDs then at least they would use a different xlate function. Another >>> option to consider would be defining the #interrupt-cells = <3> where we >>> would have ... >>> >>> cell-#1 --> IRQ domain ID >>> cell-#2 --> Trigger type >>> cell-#3 --> GPIO ID >>> >>> Then we could have a generic xlate for 3 cells that would also request >>> the GPIO. Again not sure if people are against a gpio being requested in >>> the xlate but just an idea. Or given that irq_of_parse_and_map() calls >>> the xlate, we could have this function call gpio_request() if the >>> interrupt controller is a gpio and there are 3 cells. >> >> I rather dislike this approach since: >> >> a) It requires changes to the DT bindings, which are already defined. >> Admittedly it's backwards-compatible, but still. >> >> b) There isn't really any need for the DT to represent this; the >> GPIO+IRQ driver itself already knows which IRQ ID is which GPIO ID and >> vice-versa (if the HW has such a concept), so there's no need for the DT >> to contain this information. This seems like pushing Linux's internal >> requirements into the design of the DT binding. > > Yes, so the only alternative is to use irq_to_gpio to avoid this. > >> c) I have the feeling that hooking the of_xlate function for this is a >> bit of an abuse of the function. > > I was wondering about that. So I was grep'ing through the various xlate > implementations and found this [1]. Also you may recall that in the > of_dma_simple_xlate() we call the dma_request_channel() to allocate the > channel, which is very similar. However, I don't wish to get a > reputation as abusing APIs so would be good to know if this really is > abuse or not ;-) > > Cheers > Jon > > [1] http://permalink.gmane.org/gmane.linux.ports.arm.kernel/195124 > Interesting. This is really something that the core DT and GPIO and IRQ maintainers should weigh in on. Hence, changing them from Cc: to To: in this message and/or adding them. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
