linux-kernel - Re: [PATCH v3 1/4] util_macros.h: add find

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Message-ID: <CAMpxmJV7TuKS8cfUn7sq6+-GpyjJ9X=FrR_+HD_dpWLZxv8+OA@mail.gmail.com>
Date:	Thu, 19 Mar 2015 17:21:01 +0100
From:	Bartosz Golaszewski <bgolaszewski@...libre.com>
To:	Joe Perches <joe@...ches.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Guenter Roeck <linux@...ck-us.net>,
	lm-sensors <lm-sensors@...sensors.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH v3 1/4] util_macros.h: add find_closest() macro

2015-03-19 16:15 GMT+01:00 Joe Perches <joe@...ches.com>:
> On Thu, 2015-03-19 at 15:30 +0100, Bartosz Golaszewski wrote:
>> Searching for the member of an array closest to 'x' is
>> duplicated in several places.
> []
>> diff --git a/include/linux/util_macros.h b/include/linux/util_macros.h
> []
>> @@ -0,0 +1,39 @@
>> +#ifndef _LINUX_HELPER_MACROS_H_
>> +#define _LINUX_HELPER_MACROS_H_
>> +
>> +#define __find_closest(x, a, as, op)(                                        \
>> +{                                                                    \
>> +     typeof(as) _i, _as = (as) - 1;                                  \
>> +     typeof(x) _x = (x);                                             \
>> +     typeof(*a) *_a = (a);                                           \
>> +     for (_i = 0; _i < _as; _i++) {                                  \
>> +             if (_x op DIV_ROUND_CLOSEST(_a[_i] + _a[_i + 1], 2))    \
>> +                     break;                                          \
>> +     }                                                               \
>> +     (_i);                                                           \
>> +})
>
> Please use consistent statement expression start/top whitespace.
>
>> +
>> +/*
>
> This should be /** for proper kernel-doc style
>
>> + * find_closest - locate the closest element in a sorted array
>> + * @x: The reference value.
>> + * @a: The array in which to look for the closest element. Must be sorted
>> + *  in ascending order.
>> + * @as: Size of 'a'.
>> + *
>> + * Returns the index of the element closest to 'x'.
>> + */
>> +#define find_closest(x, a, as) __find_closest(x, a, as, <=)
>> +
>> +/*
>> + * find_closest_descending - locate the closest element in a sorted array
>> + * @x: The reference value.
>> + * @a: The array in which to look for the closest element. Must be sorted
>> + *  in descending order.
>> + * @as: Size of 'a'.
>> + *
>> + * Similar to get_closest() but 'a' is expected to be sorted in descending
>> + * order.
>> + */
>> +#define find_closest_descending(x, a, as) __find_closest(x, a, as, >)
>
> Again, why is this > not >= ?

Hi Joe,

sorry I missed your comment last time. You're right of course. My
reasoning was this: the only caller of find_closest_descending()
(w83795) used '>' previously, so let's stay compatible. After giving
it some testing thought, it turned out that when using '>' the value
closest to 2 in pwm_freq_cksel0 is... 1. I'll fix that in the next
iteration.

Best regards,
Bartosz Golaszewski
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