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

[Michael Walle]

Am 2020-04-16 11:20, schrieb Linus Walleij:
> On Tue, Apr 14, 2020 at 9:57 PM Michael Walle <michael@xxxxxxxx> wrote:
>
> > So what about the following:
> >
> > #define GPIO_REGMAP_ADDR_ZERO (unsigned int)(-1)
>
> Yeah with regmap explicitly using int I guess we can't use
> S32_MAX, so that is fair.
>
> > So this way the user might assign the base addresses the normal way
> > except when he wants to use zero, in that case he has to use
> >
> >    ->base_adr = GPIO_REGMAP_ADDR_ZERO;
> >
> > gpio-regmap.c could use then:
> >
> > if (base_addr)
> >    something_useful(gpio_regmap_addr(base_addr));
> >
> > unsigned int gpio_regmap_addr(unsigned int addr)
> > {
> >    return (addr == GPIO_REGMAP_ADDR_ZERO) ? 0 : addr;
> > }
>
> That's reasonably clean.

Ok, at least on that side. For my sl28 gpio driver I then have
the problem that depending on 'base' I might have to use
GPIO_REGMAP_ADDR_ZERO:

  #define GPIO_REG_DIR 0
  config.reg_dir_out_base = base + GPIO_REG_DIR;

So there is still a convenience macro:
  #define GPIO_REGMAP_ADDR(addr) ((addr) ? addr : GPIO_REGMAP_ADDR_ZERO)

which you can use if you can't be sure that the address is not non-zero.
So the code in my sl28 gpio driver looks like:

 config.reg_dir_out_base = GPIO_REGMAP_ADDR(base + GPIO_REG_DIR);

I'll respin the patch with the current remarks.

-michael