svn commit: r274922 - head/sys/dev/ath/ath_hal/ar5212

[Dimitry Andric]

Author: dim
Date: Sun Nov 23 18:31:55 2014
New Revision: 274922
URL: https://svnweb.freebsd.org/changeset/base/274922

Log:
  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
  MFC after:	3 days
  Differential Revision: https://reviews.freebsd.org/D1212

Modified:
  head/sys/dev/ath/ath_hal/ar5212/ar5212_reset.c

Modified: head/sys/dev/ath/ath_hal/ar5212/ar5212_reset.c
==============================================================================
--- head/sys/dev/ath/ath_hal/ar5212/ar5212_reset.c	Sun Nov 23 17:47:12 2014	(r274921)
+++ head/sys/dev/ath/ath_hal/ar5212/ar5212_reset.c	Sun Nov 23 18:31:55 2014	(r274922)
@@ -2605,6 +2605,12 @@ ar5212GetTargetPowers(struct ath_hal *ah
 		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, ui
 		 * 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;
 		}