/**
* snd_ac97_update_bits - update the bits on the given register
* @ac97: the ac97 instance
* @reg: the register to change
* @mask: the bit-mask to change
* @value: the value to set
*
* Updates the masked-bits on the given register only when the value
* is changed.
*
* Returns 1 if the bits are changed, 0 if no change, or a negative
* code on failure.
*/
If the intent is to update _only_ the bits given in the mask, as the
comment seems to suggest, then the current code won't do it.
Specifically, it'll clobber unset bits that are _not_ in the mask, if
the new bit is set. Here's a fix:
diff -r bc7ef767d0cf pci/ac97/ac97_codec.c
--- a/pci/ac97/ac97_codec.c Wed Nov 29 15:29:40 2006 +0100
+++ b/pci/ac97/ac97_codec.c Fri Dec 1 02:04:30 2006 -0500
@@ -389,7 +389,7 @@ int snd_ac97_update_bits_nolock(struct s
unsigned short old, new;
old = snd_ac97_read_cache(ac97, reg);
- new = (old & ~mask) | value;
+ new = (old & ~mask) | (value & mask);
change = old != new;
if (change) {
ac97->regs[reg] = new;
@@ -406,7 +406,7 @@ static int snd_ac97_ad18xx_update_pcm_bi
mutex_lock(&ac97->page_mutex);
old = ac97->spec.ad18xx.pcmreg[codec];
- new = (old & ~mask) | value;
+ new = (old & ~mask) | (value & mask);
change = old != new;
if (change) {
mutex_lock(&ac97->reg_mutex);
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