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Date:   Thu, 16 Apr 2020 11:34:26 +0200
From:   Michael Walle <michael@walle.cc>
To:     Linus Walleij <linus.walleij@linaro.org>
Cc:     Bartosz Golaszewski <bgolaszewski@baylibre.com>,
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Subject: Re: [PATCH v2 10/16] gpio: add a reusable generic gpio_chip using
 regmap
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Am 2020-04-16 11:20, schrieb Linus Walleij:
> On Tue, Apr 14, 2020 at 9:57 PM Michael Walle <michael@walle.cc> 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