Messages in this thread | | | Date | Tue, 21 Apr 2020 12:50:59 +0200 | From | Michael Walle <> | Subject | Re: [PATCH v2 10/16] gpio: add a reusable generic gpio_chip using regmap |
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Hi Linus,
Am 2020-04-17 08:34, schrieb Michael Walle: > Hi Linus, > > Am 2020-04-16 11:27, schrieb Linus Walleij: >> On Thu, Apr 2, 2020 at 10:37 PM Michael Walle <michael@walle.cc> >> wrote: >> >>> There are quite a lot simple GPIO controller which are using regmap >>> to >>> access the hardware. This driver tries to be a base to unify existing >>> code into one place. This won't cover everything but it should be a >>> good >>> starting point. >>> >>> It does not implement its own irq_chip because there is already a >>> generic one for regmap based devices. Instead, the irq_chip will be >>> instanciated in the parent driver and its irq domain will be >>> associate >>> to this driver. >>> >>> For now it consists of the usual registers, like set (and an optional >>> clear) data register, an input register and direction registers. >>> Out-of-the-box, it supports consecutive register mappings and >>> mappings >>> where the registers have gaps between them with a linear mapping >>> between >>> GPIO offset and bit position. For weirder mappings the user can >>> register >>> its own .xlate(). >>> >>> Signed-off-by: Michael Walle <michael@walle.cc> >> >> Overall I really like this driver and I think we should merge is as >> soon >> as it is in reasonable shape and then improve on top so we can start >> migrating drivers to it. >> >>> +static int gpio_regmap_to_irq(struct gpio_chip *chip, unsigned int >>> offset) >>> +{ >>> + struct gpio_regmap_data *data = gpiochip_get_data(chip); >>> + struct gpio_regmap *gpio = data->gpio; >>> + >>> + /* the user might have its own .to_irq callback */ >>> + if (gpio->to_irq) >>> + return gpio->to_irq(gpio, offset); >>> + >>> + return irq_create_mapping(gpio->irq_domain, offset); >> >> I think that should at least be irq_find_mapping(), the mapping should >> definately not be created by the .to_irq() callback since that is just >> a convenience function. > > what do you mean by conenience function? are there other ways? if you > use > irq_find_mapping() who will create the mappings? most gpio drivers use > a > similar function like gpio_regmap_to_irq(). > >> >>> + if (gpio->irq_domain) >>> + chip->to_irq = gpio_regmap_to_irq; >> >> I don't know about this. >> (...) >>> + * @irq_domain: (Optional) IRQ domain if the >>> controller is >>> + * interrupt-capable >> (...) >>> + struct irq_domain *irq_domain; >> >> I don't think this is a good storage place for the irqdomain, we >> already have >> gpio_irq_chip inside gpio_chip and that has an irqdomain, we should >> strive to reuse that infrastructure also for regmap GPIO I think, for >> now >> I would just leave .to_irq() out of this and let the driver deal with >> any >> irqs. > > How would a driver attach the to_irq callback then? At the moment, the > gpio_regmap doesn't expose the gpio_chip. So either we have to do that > or > the config still have to have a .to_irq property.
Also, if I move the interrupt hanling completely out of the gpio-regmap, the driver would have to deal with "struct gpio_chip" which I would like to avoid if possible and keep it private to gpio-regmap.
Unfortunately, I don't have much experience how a good API for the interrupt handling and the gpio-regmap might look like. And there seems to be some overlap between regmap-irq and the interrupt stuff in gpiolib. For example, both provide and set the irq_domain_ops. Thus handing the domain over to gpio-regmap looked like a good idea to me. I get you point, that there is already a irqdomain in gpiolib and also a _to_irq() which is the same as the current implementation in gpio-regmap. Maybe it makes sense to just have a new function
int gpiolib_add_irqdomain(struct gpio_chip *gc, struct irq_domain domain) { gc->irq.domain = domain; gc->to_irq = gpiochip_to_irq; }
which is called by gpio_regmap_register() if a config->irq_domain is given.
-michael
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