[PATCH v5 1/4] uapi: Provide DIV_ROUND_CLOSEST()

Cristian Ciocaltea
2026-01-27T08:45:57Z

Currently DIV_ROUND_CLOSEST() is only available for the kernel via
include/linux/math.h.

Expose it to userland as well by adding __KERNEL_DIV_ROUND_CLOSEST() as
a common definition in uapi.

Additionally, ensure it allows building ISO C applications by switching
from the 'typeof' GNU extension to the ISO-friendly __typeof__.

Reviewed-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Tested-by: Diederik de Haas <diederik@cknow-tech.com>
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
---
include/linux/math.h | 18 +-----------------
include/uapi/linux/const.h | 17 +++++++++++++++++
2 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/include/linux/math.h b/include/linux/math.h
index 6dc1d1d32fbc..1e8fb3efbc8c 100644
--- a/include/linux/math.h
+++ b/include/linux/math.h
@@ -89,23 +89,7 @@
} \
)

-/*
- * Divide positive or negative dividend by positive or negative divisor
- * and round to closest integer. Result is undefined for negative
- * divisors if the dividend variable type is unsigned and for negative
- * dividends if the divisor variable type is unsigned.
- */
-#define DIV_ROUND_CLOSEST(x, divisor)( \
-{ \
- typeof(x) __x = x; \
- typeof(divisor) __d = divisor; \
- (((typeof(x))-1) > 0 || \
- ((typeof(divisor))-1) > 0 || \
- (((__x) > 0) == ((__d) > 0))) ? \
- (((__x) + ((__d) / 2)) / (__d)) : \
- (((__x) - ((__d) / 2)) / (__d)); \
-} \
-)
+#define DIV_ROUND_CLOSEST __KERNEL_DIV_ROUND_CLOSEST
/*
* Same as above but for u64 dividends. divisor must be a 32-bit
* number.
diff --git a/include/uapi/linux/const.h b/include/uapi/linux/const.h
index b8f629ef135f..471877322f47 100644
--- a/include/uapi/linux/const.h
+++ b/include/uapi/linux/const.h
@@ -50,4 +50,21 @@

#define __KERNEL_DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))

+/*
+ * Divide positive or negative dividend by positive or negative divisor
+ * and round to closest integer. Result is undefined for negative
+ * divisors if the dividend variable type is unsigned and for negative
+ * dividends if the divisor variable type is unsigned.
+ */
+#define __KERNEL_DIV_ROUND_CLOSEST(x, divisor)( \
+{ \
+ __typeof__(x) __x = x; \
+ __typeof__(divisor) __d = divisor; \
+ (((__typeof__(x))-1) > 0 || \
+ ((__typeof__(divisor))-1) > 0 || \
+ (((__x) > 0) == ((__d) > 0))) ? \
+ (((__x) + ((__d) / 2)) / (__d)) : \
+ (((__x) - ((__d) / 2)) / (__d)); \
+} \
+)
#endif /* _UAPI_LINUX_CONST_H */

--
2.52.0