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 -- 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
