[alsa-devel] [PATCH] ALSA: snd-usb: fix sync pipe check

[Daniel Mack]

Fix a bogus sanity check for sync pipe in pcm.c. This flaw was
introduced during the streaming logic refactorization.

While at it, improve the error messages that are generated in such cases.

Signed-off-by: Daniel Mack <zonque at gmail.com>
Reported-and-tested-by: <ben at b1c1l1.com>
---
 sound/usb/pcm.c |   18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index cdf8b76..fc7ce7c 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -354,17 +354,21 @@ static int set_format(struct snd_usb_substream *subs, struct audioformat *fmt)
 		    (get_endpoint(alts, 1)->bLength >= USB_DT_ENDPOINT_AUDIO_SIZE &&
 		     get_endpoint(alts, 1)->bSynchAddress != 0 &&
 		     !implicit_fb)) {
-			snd_printk(KERN_ERR "%d:%d:%d : invalid synch pipe\n",
-				   dev->devnum, fmt->iface, fmt->altsetting);
+			snd_printk(KERN_ERR "%d:%d:%d : invalid sync pipe. bmAttributes %02x, bLength %d, bSynchAddress %02x\n",
+				   dev->devnum, fmt->iface, fmt->altsetting,
+				   get_endpoint(alts, 1)->bmAttributes,
+				   get_endpoint(alts, 1)->bLength,
+				   get_endpoint(alts, 1)->bSynchAddress);
 			return -EINVAL;
 		}
 		ep = get_endpoint(alts, 1)->bEndpointAddress;
-		if (get_endpoint(alts, 0)->bLength >= USB_DT_ENDPOINT_AUDIO_SIZE &&
+		if (!implicit_fb &&
+		    get_endpoint(alts, 0)->bLength >= USB_DT_ENDPOINT_AUDIO_SIZE &&
 		    (( is_playback && ep != (unsigned int)(get_endpoint(alts, 0)->bSynchAddress | USB_DIR_IN)) ||
-		     (!is_playback && ep != (unsigned int)(get_endpoint(alts, 0)->bSynchAddress & ~USB_DIR_IN)) ||
-		     ( is_playback && !implicit_fb))) {
-			snd_printk(KERN_ERR "%d:%d:%d : invalid synch pipe\n",
-				   dev->devnum, fmt->iface, fmt->altsetting);
+		     (!is_playback && ep != (unsigned int)(get_endpoint(alts, 0)->bSynchAddress & ~USB_DIR_IN)))) {
+			snd_printk(KERN_ERR "%d:%d:%d : invalid sync pipe. is_playback %d, ep %02x, bSynchAddress %02x\n",
+				   dev->devnum, fmt->iface, fmt->altsetting,
+				   is_playback, ep, get_endpoint(alts, 0)->bSynchAddress);
 			return -EINVAL;
 		}
 
-- 
1.7.10.2