linux-kernel - Re: [RFC PATCH] gpiolib: Refactor gpio

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Date:	Fri, 19 Oct 2012 23:43:35 +0100
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Ryan Mallon <rmallon@...il.com>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] gpiolib: Refactor gpio_export

On Fri, Oct 19, 2012 at 11:14 PM, Ryan Mallon <rmallon@...il.com> wrote:
> On 19/10/12 21:07, Linus Walleij wrote:
>
>> On Wed, Oct 17, 2012 at 1:41 AM, Ryan Mallon <rmallon@...il.com> wrote:
>>
>>> The gpio_export function uses nested if statements and the status
>>> variable to handle the failure cases. This makes the function logic
>>> difficult to follow. Refactor the code to abort immediately on failure
>>> using goto. This makes the code slightly longer, but significantly
>>> reduces the nesting and number of split lines and makes the code easier
>>> to read.
>>>
>>> Signed-off-by: Ryan Mallon
>>
>> Very good initiative!
>>
>>> +++ b/drivers/gpio/gpiolib.c
>>> @@ -702,68 +702,74 @@ int gpio_export(unsigned gpio, bool direction_may_change)
>>>  {
>>>         unsigned long           flags;
>>>         struct gpio_desc        *desc;
>>> -       int                     status = -EINVAL;
>>> +       int                     status;
>>>         const char              *ioname = NULL;
>>> +       struct device           *dev;
>>>
>>>         /* can't export until sysfs is available ... */
>>>         if (!gpio_class.p) {
>>>                 pr_debug("%s: called too early!\n", __func__);
>>> -               return -ENOENT;
>>> +               status = -ENOENT;
>>> +               goto fail;
>>
>> Why bother with all the goto:s here since there are no resources
>> to clean up? Just pr_debug() and return -ENOENT; is good enough.
>>
>> I don't quite see the point.
>
> I did it this way just so that there would be a single exit point.
> I don't mind either way, so I'll update the ones without any
> clean up to simply return.

Single exit points are overrated. The code is shorter and easier to
read to return immediately if there isn't any unwinding to do.

g.
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