On Tue 08 Sep 05:20 PDT 2015, Linus Walleij wrote: > On Thu, Aug 27, 2015 at 7:37 PM, Bjorn Andersson > <bjorn.andersson@xxxxxxxxxxxxxx> wrote: > > Let's discuss this a bit, looping in Mark Brown. > > > As some of these states on some platforms are passed as physical signals > > instead, the two drivers are modelled as gpio- and interrupt-controllers - > > providing a nice abstraction both in device tree sense and Linux implementation > > sense. > > I have unfortunately repeatedly encountered an argument of the type > "GPIO has nice infrastructure so let's call X 'a kind of GPIO' so > we can use that nice infrastructure". > I guess that's what you get for maintaining a subsystem with "general purpose" in the name ;) Sorry for adding one more item to your list. > I'm not pleased with something that is not really general purpose > input/output being called GPIO. It fits badly with the GPIO subsystem > when we support things like open drain and cross-mappings to > the pin control subsystem that will never be applicable to these > new users. It's more like "special purpose input/output" or > something. > Right, this doesn't match at all with the electrical properties. What it does give is the nice symmetry with the irq bits and existing apis for poking and peeking. > This happened with syscon LEDs for example, and was the reason > I implemented syscon-leds. The original proposal was to say the LEDs > register was "a kind of GPIO" on top of regmap and then use gpio-leds > on top of that. Instead I insisted it was a syscon/regmap and the > LEDs go directly to that, bypassing one layer of abstraction. > > I also imagine creating syscon-keys.c for input from arbitrary keys > in a syscon register actually. Just didn't get around to that yet. > The difference with those two cases is that the pieces didn't fit together, so we tried to use the gpio framework as an adaptor to make it work. I picked the gpio framework because: * the DT nicely represent the structure of the memory and relationship between the individual components. * the implementation needs to be able to set and clear individual bits, as well as register handlers for state changes. * I'm told the SMP2P entries are on some platform (I've never seen) actual gpio lines. > I also see some of the stuff GPIO does out-of-the-box being useful, > for example in MFD: some of these are interrupt controllers and > basically duplicate the kind of code I have in gpiolib for > GPIOLIB_IRQCHIP. > I do learn about new helper functions every time I touch these things. > So we need to figure out what is really needed. > > While sparsely documented: what about regmap (maybe in the > form of syscon) and drivers/base/regmap/regmap-irq.c for the > interrupt handling? > regmap-irq looks good and reasonable. The problem is that for SMSM I need custom masking operations and on SMP2P I have multiple regmaps sharing one incoming IRQ. So it doesn't look applicable for my use cases. > I cannot claim to understand regmap-irq.c, but I just intuitively > think it deserves consideration, such that drivers who need one > of these misc registers can read/write their bits with regmap > accessors and also get IRQs by way of regmap-irq. > I was expecting some push back from you, but as it was the cleanest abstraction I would come up with I gave it a shot :) I'll rewrite the outgoing part based on regmaps instead. Thanks for reviewing. Regards, Bjorn -- 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
