Hi Andy,
On Wed, 14 Jun 2023 12:02:57 +0300 Andy Shevchenko andy.shevchenko@gmail.com wrote:
On Wed, Jun 14, 2023 at 10:49 AM Herve Codina herve.codina@bootlin.com wrote:
Introduce min_array() (resp max_array()) in order to get the minimal (resp maximum) of values present in an array.
Reviewed-by: Andy Shevchenko andy.shevchenko@gmail.com See a remark below.
Signed-off-by: Herve Codina herve.codina@bootlin.com
include/linux/minmax.h | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+)
diff --git a/include/linux/minmax.h b/include/linux/minmax.h index 396df1121bff..2cd0d34ce921 100644 --- a/include/linux/minmax.h +++ b/include/linux/minmax.h @@ -133,6 +133,42 @@ */ #define max_t(type, x, y) __careful_cmp((type)(x), (type)(y), >)
+/*
- Do not check the array parameter using __must_be_array().
- In the following legit use-case where the "array" passed is a simple pointer,
- __must_be_array() will return a failure.
- --- 8< ---
- int *buff
- ...
- min = min_array(buff, nb_items);
- --- 8< ---
- */
+#define __minmax_array(op, array, len) ({ \
typeof(array) __array = (array); \typeof(len) __len = (len); \typeof(__array[0] + 0) __element = __array[--__len]; \Do we need the ' + 0' part?
Yes.
__array can be an array of const items and it is legitimate to get the minimum value from const items.
typeof(__array[0]) keeps the const qualifier but we need to assign __element in the loop. One way to drop the const qualifier is to get the type from a rvalue computed from __array[0]. This rvalue has to have the exact same type with only the const dropped. '__array[0] + 0' was a perfect canditate.
Regards, Hervé
while (__len--) \__element = op(__element, __array[__len]); \__element; })+/**
- min_array - return minimum of values present in an array
- @array: array
- @len: array length
- Note that @len must not be zero (empty array).
- */
+#define min_array(array, len) __minmax_array(min, array, len)
+/**
- max_array - return maximum of values present in an array
- @array: array
- @len: array length
- Note that @len must not be zero (empty array).
- */
+#define max_array(array, len) __minmax_array(max, array, len)
/**
- clamp_t - return a value clamped to a given range using a given type
- @type: the type of variable to use
-- 2.40.1