MFC r274922:

Fix the following -Werror warning from clang 3.5.0, while building the
ath kernel module:

sys/dev/ath/ath_hal/ar5212/ar5212_reset.c:2642:7: error: taking the absolute value of unsigned type 'unsigned int' has no effect [-Werror,-Wabsolute-value]
                if (abs(lp[0] * EEP_SCALE - target) < EEP_DELTA) {
                    ^
sys/dev/ath/ah_osdep.h:74:18: note: expanded from macro 'abs'
#define abs(_a)         __builtin_abs(_a)
                        ^
sys/dev/ath/ath_hal/ar5212/ar5212_reset.c:2642:7: note: remove the call to '__builtin_abs' since unsigned values cannot be negative
sys/dev/ath/ah_osdep.h:74:18: note: expanded from macro 'abs'
#define abs(_a)         __builtin_abs(_a)
                        ^
1 error generated.

This warning occurs because both lp[0] and target are unsigned, so the
subtraction expression is also unsigned, and calling abs() is a no-op.

However, the intention was to look at the absolute difference between
the two unsigned quantities.  Introduce a small static function to
clarify what we're doing, and call that instead.

Reviewed by:	adrian
Differential Revision: https://reviews.freebsd.org/D1212

1 files changed, 7 insertions, 1 deletions

diff --git a/sys/dev/ath/ath_hal/ar5212/ar5212_reset.c b/sys/dev/ath/ath_hal/ar5212/ar5212_reset.c
index eca2e1f..ccdccb6 100644
--- a/sys/dev/ath/ath_hal/ar5212/ar5212_reset.c
+++ b/sys/dev/ath/ath_hal/ar5212/ar5212_reset.c
@@ -2605,6 +2605,12 @@ ar5212GetTargetPowers(struct ath_hal *ah, const struct ieee80211_channel *chan,
 		powInfo[ixlo].twicePwr54, powInfo[ixhi].twicePwr54);
 }
 
+static uint32_t
+udiff(uint32_t u, uint32_t v)
+{
+	return (u >= v ? u - v : v - u);
+}
+
 /*
  * Search a list for a specified value v that is within
  * EEP_DELTA of the search values.  Return the closest
@@ -2639,7 +2645,7 @@ ar5212GetLowerUpperValues(uint16_t v, uint16_t *lp, uint16_t listSize,
 		 * If value is close to the current value of the list
 		 * then target is not between values, it is one of the values
 		 */
-		if (abs(lp[0] * EEP_SCALE - target) < EEP_DELTA) {
+		if (udiff(lp[0] * EEP_SCALE, target) < EEP_DELTA) {
 			*vlo = *vhi = lp[0];
 			return;
 		}