linux-kernel - Re: [PATCH] gpio: introduce gpio_request

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Message-ID: <f17812d71001121923k5a67c42flb92cf7bb2c8a0b5a@mail.gmail.com>
Date:	Wed, 13 Jan 2010 11:23:54 +0800
From:	Eric Miao <eric.y.miao@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	David Brownell <david-b@...bell.net>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpio: introduce gpio_request_one() and friends

On Wed, Jan 13, 2010 at 7:09 AM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Fri, 8 Jan 2010 13:28:57 +0800
> Eric Miao <eric.y.miao@...il.com> wrote:
>
>> Typo in GPIOF_* definitions, updated patch follows:
>>
>> commit 29cd35f57699fd93a12132186d52109a55ed57e7
>> Author: Eric Miao <eric.y.miao@...il.com>
>> Date:   Fri Jan 8 12:16:28 2010 +0800
>>
>>     gpio: introduce gpio_request_one() and friends
>>
>>     gpio_request() without initial configuration of the GPIO is normally
>>     useless, introduce gpio_request_one() together with GPIOF_ flags for
>>     input/output direction and initial output level.
>>
>>     gpio_{request,free}_array() for multiple GPIOs.
>>
>>     Cc: David Brownell <dbrownell@...rs.sourceforge.net>
>>     Signed-off-by: Eric Miao <eric.y.miao@...il.com>
>>
>> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
>> index a25ad28..e80a1f8 100644
>> --- a/drivers/gpio/gpiolib.c
>> +++ b/drivers/gpio/gpiolib.c
>> @@ -1239,6 +1239,48 @@ void gpio_free(unsigned gpio)
>>  }
>>  EXPORT_SYMBOL_GPL(gpio_free);
>>
>> +int gpio_request_one(unsigned gpio, unsigned long flags, const char *label)
>> +{
>> +     int err;
>> +
>> +     err = gpio_request(gpio, label);
>> +     if (err)
>> +             return err;
>> +
>> +     if (flags & GPIOF_DIR_IN)
>> +             err = gpio_direction_input(gpio);
>> +     else
>> +             err = gpio_direction_output(gpio,
>> +                             (flags & GPIOF_INIT_HIGH) ? 1 : 0);
>> +
>> +     return err;
>> +}
>> +EXPORT_SYMBOL_GPL(gpio_request_one);
>> +
>> +int gpio_request_array(struct gpio *array, size_t num)
>> +{
>> +     int i, err;
>> +
>> +     for (i = 0; i < num; i++, array++) {
>> +             err = gpio_request_one(array->gpio, array->flags, array->label);
>> +             if (err)
>> +                     goto err_free;
>> +     }
>> +     return 0;
>> +
>> +err_free:
>> +     while (i--)
>> +             gpio_free((--array)->gpio);
>> +     return err;
>> +}
>> +EXPORT_SYMBOL_GPL(gpio_request_array);
>> +
>> +void gpio_free_array(struct gpio *array, size_t num)
>> +{
>> +     while (num--)
>> +             gpio_free((array++)->gpio);
>> +}
>> +EXPORT_SYMBOL_GPL(gpio_free_array);
>
> Global, exported-to-modules interfaces should be documented, IMO.
>

OK, will do.

>>  /**
>>   * gpiochip_is_requested - return string iff signal was requested
>> diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
>> index 485eeb6..a9e0b94 100644
>> --- a/include/asm-generic/gpio.h
>> +++ b/include/asm-generic/gpio.h
>> @@ -136,6 +136,26 @@ extern int __gpio_cansleep(unsigned gpio);
>>
>>  extern int __gpio_to_irq(unsigned gpio);
>>
>> +#define GPIOF_DIR_OUT        (0 << 0)
>> +#define GPIOF_DIR_IN (1 << 0)
>> +
>> +#define GPIOF_INIT_LOW       (0 << 1)
>> +#define GPIOF_INIT_HIGH      (1 << 1)
>> +
>> +#define GPIOF_IN             (GPIOF_DIR_IN)
>> +#define GPIOF_OUT_INIT_LOW   (GPIOF_DIR_OUT | GPIOF_INIT_LOW)
>> +#define GPIOF_OUT_INIT_HIGH  (GPIOF_DIR_OUT | GPIOF_INIT_HIGH)
>> +
>> +struct gpio {
>> +     unsigned        gpio;
>> +     unsigned long   flags;
>> +     const char      *label;
>> +};
>
> hm.  Was "struct gpio" a well-chosen identifier?  The name implies that
> this structure is the definitive, unified, generic kernel-wide
> representation of a "gpio", whatever that is.
>

These three fields should be sufficient to support future requirements
of GPIO by using additional flags (e.g. open-drain capable can be
actually made a flag quite easy here), so in my opinion - yes, this
should be a proper name.

>> +extern int gpio_request_one(unsigned gpio, unsigned long flags, const
>> char *label);
>
> Your email client is wordwrapping the patches.
>

Sorry.
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