linux-kernel - Re: [PATCH 5/8] gpio: exar: Fix reading of directions and values

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Message-ID: <CAHp75Ve3wA6AUTRA7RwFVBS=w5ntdwak+mTJN5tE_n7oW+JQvw@mail.gmail.com>
Date:   Thu, 18 May 2017 13:11:09 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Jan Kiszka <jan.kiszka@...mens.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alexandre Courbot <gnurou@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Sudip Mukherjee <sudip.mukherjee@...ethink.co.uk>,
        Sascha Weisenberger <sascha.weisenberger@...mens.com>
Subject: Re: [PATCH 5/8] gpio: exar: Fix reading of directions and values

On Thu, May 18, 2017 at 8:20 AM, Jan Kiszka <jan.kiszka@...mens.com> wrote:
> On 2017-05-13 15:36, Andy Shevchenko wrote:
>> On Sat, May 13, 2017 at 10:29 AM, Jan Kiszka <jan.kiszka@...mens.com> wrote:
>>> First, the logic for translating a register bit to the return code of
>>> exar_get_direction and exar_get_value were wrong. And second, there was
>>> a flip regarding the register bank in exar_get_direction.
>>
>> Again, I wish it was tested in the first place.
>>
>> After addressing below:
>> FWIW:
>> Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
>>
>>> @@ -68,7 +68,7 @@ static int exar_get(struct gpio_chip *chip, unsigned int reg)
>>>         value = readb(exar_gpio->regs + reg);
>>>         mutex_unlock(&exar_gpio->lock);
>>>
>>> -       return !!value;
>>> +       return value;
>>
>> This one is correct.

>>
>>> @@ -80,7 +80,7 @@ static int exar_get_direction(struct gpio_chip *chip, unsigned int offset)
>>>         addr = bank ? EXAR_OFFSET_MPIOSEL_HI : EXAR_OFFSET_MPIOSEL_LO;
>>>         val = exar_get(chip, addr) >> (offset % 8);
>>>
>>> -       return !!val;
>>> +       return val & 1;
>>
>> It should be rather
>>
>>         val = exar_get(chip, addr) & BIT(offset % 8);
>
> That won't give us 0 or 1 as return value, thus would be incorrect.

Full picture:

 val = exar_get(chip, addr) & BIT(offset % 8);

 return !!val;

How it could be non-(1 or 0)?

-- 
With Best Regards,
Andy Shevchenko