Re: [PATCH v2 10/16] gpio: add a reusable generic gpio_chip using regmap

Michael Walle
2020-04-17T06:34:20Z

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.

-michael