--- /dev/null
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_MINMAX_H
+#define _LINUX_MINMAX_H
+
+#include <linux/compiler.h>
+#include <linux/const.h>
+#include <linux/types.h>
+
+/*
+ * min()/max()/clamp() macros must accomplish three things:
+ *
+ * - Avoid multiple evaluations of the arguments (so side-effects like
+ * "x++" happen only once) when non-constant.
+ * - Retain result as a constant expressions when called with only
+ * constant expressions (to avoid tripping VLA warnings in stack
+ * allocation usage).
+ * - Perform signed v unsigned type-checking (to generate compile
+ * errors instead of nasty runtime surprises).
+ * - Unsigned char/short are always promoted to signed int and can be
+ * compared against signed or unsigned arguments.
+ * - Unsigned arguments can be compared against non-negative signed constants.
+ * - Comparison of a signed argument against an unsigned constant fails
+ * even if the constant is below __INT_MAX__ and could be cast to int.
+ */
+#define __typecheck(x, y) \
+ (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
+
+/* is_signed_type() isn't a constexpr for pointer types */
+#define __is_signed(x) \
+ __builtin_choose_expr(__is_constexpr(is_signed_type(typeof(x))), \
+ is_signed_type(typeof(x)), 0)
+
+/* True for a non-negative signed int constant */
+#define __is_noneg_int(x) \
+ (__builtin_choose_expr(__is_constexpr(x) && __is_signed(x), x, -1) >= 0)
+
+#define __types_ok(x, y) \
+ (__is_signed(x) == __is_signed(y) || \
+ __is_signed((x) + 0) == __is_signed((y) + 0) || \
+ __is_noneg_int(x) || __is_noneg_int(y))
+
+#define __cmp_op_min <
+#define __cmp_op_max >
+
+#define __cmp(op, x, y) ((x) __cmp_op_##op (y) ? (x) : (y))
+
+#define __cmp_once(op, x, y, unique_x, unique_y) ({ \
+ typeof(x) unique_x = (x); \
+ typeof(y) unique_y = (y); \
+ static_assert(__types_ok(x, y), \
+ #op "(" #x ", " #y ") signedness error, fix types or consider u" #op "() before " #op "_t()"); \
+ __cmp(op, unique_x, unique_y); })
+
+#define __careful_cmp(op, x, y) \
+ __builtin_choose_expr(__is_constexpr((x) - (y)), \
+ __cmp(op, x, y), \
+ __cmp_once(op, x, y, __UNIQUE_ID(__x), __UNIQUE_ID(__y)))
+
+#define __clamp(val, lo, hi) \
+ ((val) >= (hi) ? (hi) : ((val) <= (lo) ? (lo) : (val)))
+
+#define __clamp_once(val, lo, hi, unique_val, unique_lo, unique_hi) ({ \
+ typeof(val) unique_val = (val); \
+ typeof(lo) unique_lo = (lo); \
+ typeof(hi) unique_hi = (hi); \
+ static_assert(__builtin_choose_expr(__is_constexpr((lo) > (hi)), \
+ (lo) <= (hi), true), \
+ "clamp() low limit " #lo " greater than high limit " #hi); \
+ static_assert(__types_ok(val, lo), "clamp() 'lo' signedness error"); \
+ static_assert(__types_ok(val, hi), "clamp() 'hi' signedness error"); \
+ __clamp(unique_val, unique_lo, unique_hi); })
+
+#define __careful_clamp(val, lo, hi) ({ \
+ __builtin_choose_expr(__is_constexpr((val) - (lo) + (hi)), \
+ __clamp(val, lo, hi), \
+ __clamp_once(val, lo, hi, __UNIQUE_ID(__val), \
+ __UNIQUE_ID(__lo), __UNIQUE_ID(__hi))); })
+
+/**
+ * min - return minimum of two values of the same or compatible types
+ * @x: first value
+ * @y: second value
+ */
+#define min(x, y) __careful_cmp(min, x, y)
+
+/**
+ * max - return maximum of two values of the same or compatible types
+ * @x: first value
+ * @y: second value
+ */
+#define max(x, y) __careful_cmp(max, x, y)
+
+/**
+ * umin - return minimum of two non-negative values
+ * Signed types are zero extended to match a larger unsigned type.
+ * @x: first value
+ * @y: second value
+ */
+#define umin(x, y) \
+ __careful_cmp(min, (x) + 0u + 0ul + 0ull, (y) + 0u + 0ul + 0ull)
+
+/**
+ * umax - return maximum of two non-negative values
+ * @x: first value
+ * @y: second value
+ */
+#define umax(x, y) \
+ __careful_cmp(max, (x) + 0u + 0ul + 0ull, (y) + 0u + 0ul + 0ull)
+
+/**
+ * min3 - return minimum of three values
+ * @x: first value
+ * @y: second value
+ * @z: third value
+ */
+#define min3(x, y, z) min((typeof(x))min(x, y), z)
+
+/**
+ * max3 - return maximum of three values
+ * @x: first value
+ * @y: second value
+ * @z: third value
+ */
+#define max3(x, y, z) max((typeof(x))max(x, y), z)
+
+/**
+ * min_not_zero - return the minimum that is _not_ zero, unless both are zero
+ * @x: value1
+ * @y: value2
+ */
+#define min_not_zero(x, y) ({ \
+ typeof(x) __x = (x); \
+ typeof(y) __y = (y); \
+ __x == 0 ? __y : ((__y == 0) ? __x : min(__x, __y)); })
+
+/**
+ * clamp - return a value clamped to a given range with strict typechecking
+ * @val: current value
+ * @lo: lowest allowable value
+ * @hi: highest allowable value
+ *
+ * This macro does strict typechecking of @lo/@hi to make sure they are of the
+ * same type as @val. See the unnecessary pointer comparisons.
+ */
+#define clamp(val, lo, hi) __careful_clamp(val, lo, hi)
+
+/*
+ * ..and if you can't take the strict
+ * types, you can specify one yourself.
+ *
+ * Or not use min/max/clamp at all, of course.
+ */
+
+/**
+ * min_t - return minimum of two values, using the specified type
+ * @type: data type to use
+ * @x: first value
+ * @y: second value
+ */
+#define min_t(type, x, y) __careful_cmp(min, (type)(x), (type)(y))
+
+/**
+ * max_t - return maximum of two values, using the specified type
+ * @type: data type to use
+ * @x: first value
+ * @y: second value
+ */
+#define max_t(type, x, y) __careful_cmp(max, (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< ---
+ *
+ * The first typeof(&(array)[0]) is needed in order to support arrays of both
+ * 'int *buff' and 'int buff[N]' types.
+ *
+ * The array can be an array of const items.
+ * typeof() keeps the const qualifier. Use __unqual_scalar_typeof() in order
+ * to discard the const qualifier for the __element variable.
+ */
+#define __minmax_array(op, array, len) ({ \
+ typeof(&(array)[0]) __array = (array); \
+ typeof(len) __len = (len); \
+ __unqual_scalar_typeof(__array[0]) __element = __array[--__len];\
+ 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
+ * @val: current value
+ * @lo: minimum allowable value
+ * @hi: maximum allowable value
+ *
+ * This macro does no typechecking and uses temporary variables of type
+ * @type to make all the comparisons.
+ */
+#define clamp_t(type, val, lo, hi) __careful_clamp((type)(val), (type)(lo), (type)(hi))
+
+/**
+ * clamp_val - return a value clamped to a given range using val's type
+ * @val: current value
+ * @lo: minimum allowable value
+ * @hi: maximum allowable value
+ *
+ * This macro does no typechecking and uses temporary variables of whatever
+ * type the input argument @val is. This is useful when @val is an unsigned
+ * type and @lo and @hi are literals that will otherwise be assigned a signed
+ * integer type.
+ */
+#define clamp_val(val, lo, hi) clamp_t(typeof(val), val, lo, hi)
+
+static inline bool in_range64(u64 val, u64 start, u64 len)
+{
+ return (val - start) < len;
+}
+
+static inline bool in_range32(u32 val, u32 start, u32 len)
+{
+ return (val - start) < len;
+}
+
+/**
+ * in_range - Determine if a value lies within a range.
+ * @val: Value to test.
+ * @start: First value in range.
+ * @len: Number of values in range.
+ *
+ * This is more efficient than "if (start <= val && val < (start + len))".
+ * It also gives a different answer if @start + @len overflows the size of
+ * the type by a sufficient amount to encompass @val. Decide for yourself
+ * which behaviour you want, or prove that start + len never overflow.
+ * Do not blindly replace one form with the other.
+ */
+#define in_range(val, start, len) \
+ ((sizeof(start) | sizeof(len) | sizeof(val)) <= sizeof(u32) ? \
+ in_range32(val, start, len) : in_range64(val, start, len))
+
+/**
+ * swap - swap values of @a and @b
+ * @a: first value
+ * @b: second value
+ */
+#define swap(a, b) \
+ do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)
+
+#endif /* _LINUX_MINMAX_H */
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