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Fix the following -Werror warning from clang 3.5.0, while building the

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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
This commit is contained in:
Dimitry Andric 2014-11-23 18:31:55 +00:00
parent 26ec349199
commit d41b89cca5
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=274922
1 changed files with 7 additions and 1 deletions
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8
sys/dev/ath/ath_hal/ar5212/ar5212_reset.c
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@ -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;
}