Add macros similar to min/max/min_t/max_t

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.

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: fix v4l build]
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Cc: Jeff Garzik <jeff@garzik.org>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Michael Buesch <mb@bu3sch.de>
Cc: "John W. Linville" <linville@tuxdriver.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Dmitry Torokhov <dtor@mail.ru>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 74 insertions, 17 deletions

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 53839ba265ec..4d46e299afb5 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -338,33 +338,90 @@ extern void print_hex_dump_bytes(const char *prefix_str, int prefix_type,
 #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; })
+
+/**
+ * clamp - return a value clamped to a given range with strict typechecking
+ * @val: current value
+ * @min: minimum allowable value
+ * @max: maximum allowable value
+ *
+ * This macro does strict typechecking of min/max to make sure they are of the
+ * same type as val.  See the unnecessary pointer comparisons.
+ */
+#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 __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; })
+
+/**
+ * clamp_t - return a value clamped to a given range using a given type
+ * @type: the type of variable to use
+ * @val: current value
+ * @min: minimum allowable value
+ * @max: maximum allowable value
+ *
+ * This macro does no typechecking and uses temporary variables of type
+ * 'type' to make all the comparisons.
  */
-#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 clamp_t(type, val, min, max) ({         \
+        type __val = (val);                     \
+        type __min = (min);                     \
+        type __max = (max);                     \
+        __val = __val < __min ? __min: __val;   \
+        __val > __max ? __max: __val; })
 
+/**
+ * clamp_val - return a value clamped to a given range using val's type
+ * @val: current value
+ * @min: minimum allowable value
+ * @max: 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 min and max are literals that will otherwise be assigned a signed
+ * integer type.
+ */
+#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