[alsa-devel] [PATCH] ALSA: snd-usb: fix clock source validity index

Daniel Mack zonque at gmail.com
Wed Aug 1 10:16:53 CEST 2012

uac_clock_source_is_valid() uses the control selector value to access
the bmControls bitmap of the clock source unit. This is wrong, as
control selector values start from 1, while the bitmap uses all
available bits.

In other words, "Clock Validity Control" is stored in D3..2, not D5..4
of the clock selector unit's bmControls.

Signed-off-by: Daniel Mack <zonque at gmail.com>
Reported-by: Andreas Koch <andreas at akdesigninc.com>
Cc: stable at kernel.org
 sound/usb/clock.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sound/usb/clock.c b/sound/usb/clock.c
index 379baad..5e634a2 100644
--- a/sound/usb/clock.c
+++ b/sound/usb/clock.c
@@ -111,7 +111,8 @@ static bool uac_clock_source_is_valid(struct snd_usb_audio *chip, int source_id)
 		return 0;
 	/* If a clock source can't tell us whether it's valid, we assume it is */
-	if (!uac2_control_is_readable(cs_desc->bmControls, UAC2_CS_CONTROL_CLOCK_VALID))
+	if (!uac2_control_is_readable(cs_desc->bmControls,
+				      UAC2_CS_CONTROL_CLOCK_VALID - 1))
 		return 1;
 	err = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0), UAC2_CS_CUR,

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