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

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Message-ID: <CAMz4kuJJpVEbvS8pUaqW6qQYo1K=y61yb+JsfU9rQ6GKNotRYw@mail.gmail.com>
Date:   Wed, 28 Feb 2018 10:22:08 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
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 27 February 2018 at 23:54, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
> On Tue, Feb 27, 2018 at 4:35 AM, Baolin Wang <baolin.wang@...aro.org> wrote:
>> On 26 February 2018 at 20:02, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
>>> 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:
>
>>>>>> +       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);
>>>
>>> ?
>>
>> It can not work, regmap_read() expects 'unsigned int *'.
>
> Ah, OK, than the temporary variable is a left approach.
>
>> But I can
>> convert it like this:
>>
>> for_each_set_bit(n, (unsigned long *)&val, chip->ngpio) {
>>          .......
>> }
>
> No, this is a boilerplate for static analyzers and definitely UB.

OK. Thanks for pointing this issue out.

-- 
Baolin.wang
Best Regards