linux-kernel - Re: [PATCH v2 3/3] gpio: Add Spreadtrum PMIC EIC driver support

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Message-ID: <CAHp75VeJiqp74LrsETHTwxd5iaOObRX5bdYXz=rYeHm-4KbgHA@mail.gmail.com>
Date:   Mon, 26 Feb 2018 14:02:41 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Baolin Wang <baolin.wang@...aro.org>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH v2 3/3] gpio: Add Spreadtrum PMIC EIC driver support

On Mon, Feb 26, 2018 at 5:01 AM, Baolin Wang <baolin.wang@...aro.org> wrote:
> On 25 February 2018 at 20:19, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
>> On Sat, Feb 24, 2018 at 12:44 PM, Baolin Wang <baolin.wang@...aro.org> wrote:

>>> +static int sprd_pmic_eic_direction_input(struct gpio_chip *chip,
>>> +                                        unsigned int offset)
>>> +{
>>> +       /* EICs are always input, nothing need to do here. */
>>> +       return 0;
>>> +}
>>> +
>>> +static void sprd_pmic_eic_set(struct gpio_chip *chip, unsigned int offset,
>>> +                             int value)
>>> +{
>>> +       /* EICs are always input, nothing need to do here. */
>>> +}
>>
>> Remove both.
>>
>> Look at what GPIO core does.
>
> I've checked the GPIO core, we need the
> sprd_pmic_eic_direction_input() returns 0, since user can set GPIOD_IN
> flag when requesting one GPIO, otherwise it will return errors.

Right. I thought it depends on presence of direction_output().

> We also need one dummy sprd_pmic_eic_set() when setting debounce for
> one GPIO, otherwise it will return errors.

This is pretty much a "feature" of GPIO framework. It shouldn't
require ->set() by logic if there is no output facility.
OK.

>>> +       for (n = 0; n < chip->ngpio; n++) {
>>> +               if (!(BIT(n) & val))
>>
>> for_each_set_bit().
>>
>> At some point you may need just to go across lib/ in the kernel and
>> see what we have there.
>
> I've considered the for_each_set_bit(), it need one 'unsigned long'
> type parameter, but we get the value from regmap is 'u32' type. So we
> need one extra conversion from 'u32' to 'unsigned long' like:
>
> unsigned long reg = val;
>
> for_each_set_bit(n, &reg, chip->ngpio) {
>         .......
> }
>
> If you like this conversion, then I can change to use
> for_each_set_bit(). Thanks.

Wouldn't it work like

unsigned long val;

...regmap_read(..., &val);

?

-- 
With Best Regards,
Andy Shevchenko