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SubjectRe: [PATCH 01/10] Add macros similar to min/max/min_t/max_t.
On Thu, 13 Mar 2008 22:18:45 -0700 Harvey Harrison wrote:

> Also, change the variable names used in the min/max macros to avoid shadowed
> variable warnings when min/max min_t/max_t are nested.
>
> Small formatting changes to make all the macros have a similar form.
>
>
> drivers/media/video/bt8xx/bttvp.h | 2 -
> drivers/media/video/usbvideo/vicam.c | 6 ---
> include/linux/kernel.h | 63 ++++++++++++++++++++++++----------
> 3 files changed, 45 insertions(+), 26 deletions(-)

> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index 2df44e7..c74460c 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -335,33 +335,60 @@ static inline int __attribute__ ((format (printf, 1, 2))) pr_debug(const char *
> #endif /* __LITTLE_ENDIAN */
>
> /*
> - * min()/max() macros that also do
> + * min()/max()/clamp() macros that also do
> * strict type-checking.. See the
> * "unnecessary" pointer comparison.
> */
> -#define min(x,y) ({ \
> - typeof(x) _x = (x); \
> - typeof(y) _y = (y); \
> - (void) (&_x == &_y); \
> - _x < _y ? _x : _y; })
> -
> -#define max(x,y) ({ \
> - typeof(x) _x = (x); \
> - typeof(y) _y = (y); \
> - (void) (&_x == &_y); \
> - _x > _y ? _x : _y; })
> +#define min(x, y) ({ \
> + typeof(x) _min1 = (x); \
> + typeof(y) _min2 = (y); \
> + (void) (&_min1 == &_min2); \
> + _min1 < _min2 ? _min1 : _min2; })
> +
> +#define max(x, y) ({ \
> + typeof(x) _max1 = (x); \
> + typeof(y) _max2 = (y); \
> + (void) (&_max1 == &_max2); \
> + _max1 > _max2 ? _max1 : _max2; })
> +

Where is some blurb/comment about what "clamp" means/does?
min/max are well understood, but clamp? Is that a shop tool?
I think I have a few out in my garage.

So can we have some blurb here to explain clamp(), clamp_t(),
and clamp_val()?

(kernel-doc preferred, but not required) e.g:


/**
* clamp - returns a value that is restricted between min & max inclusive
* @val: current value
* @min: minimum value of the clamping region
* @max: maximum value of the clamping region
*/

and explain the differences in clamp/clamp_t/clamp_val...


/*
> +#define clamp(val, min, max) ({ \
> + typeof(val) __val = (val); \
> + typeof(min) __min = (min); \
> + typeof(max) __max = (max); \
> + (void) (&__val == &__min); \
> + (void) (&__val == &__max); \
> + __val = __val < __min ? __min: __val; \
> + __val > __max ? __max: __val; })
>
> /*
> * ..and if you can't take the strict
> * types, you can specify one yourself.
> *
> - * Or not use min/max at all, of course.
> + * Or not use min/max/clamp at all, of course.
> */
> -#define min_t(type,x,y) \
> - ({ type __x = (x); type __y = (y); __x < __y ? __x: __y; })
> -#define max_t(type,x,y) \
> - ({ type __x = (x); type __y = (y); __x > __y ? __x: __y; })
> -
> +#define min_t(type, x, y) ({ \
> + type __min1 = (x); \
> + type __min2 = (y); \
> + __min1 < __min2 ? __min1: __min2; })
> +
> +#define max_t(type, x, y) ({ \
> + type __max1 = (x); \
> + type __max2 = (y); \
> + __max1 > __max2 ? __max1: __max2; })
> +
> +#define clamp_t(type, val, min, max) ({ \
> + type __val = (val); \
> + type __min = (min); \
> + type __max = (max); \
> + __val = __val < __min ? __min: __val; \
> + __val > __max ? __max: __val; })
> +
> +#define clamp_val(val, min, max) ({ \
> + typeof(val) __val = (val); \
> + typeof(val) __min = (min); \
> + typeof(val) __max = (max); \
> + __val = __val < __min ? __min: __val; \
> + __val > __max ? __max: __val; })
>
> /**
> * container_of - cast a member of a structure out to the containing structure


---
~Randy


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