[ALSA] usb-audio - sanity-check sync feedback frequency values

USB generic driver
Check that the synchronization feedback frequency values returned by the
device are more or less near the nominal frequency.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>

1 files changed, 9 insertions, 13 deletions

diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
index c360ab9783d5..a6ed0d08337e 100644
--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -452,17 +452,11 @@ static int retire_playback_sync_urb(snd_usb_substream_t *subs,
         if (urb->iso_frame_desc[0].status == 0 &&
             urb->iso_frame_desc[0].actual_length == 3) {
                 f = combine_triple((u8*)urb->transfer_buffer) << 2;
-#if 0
-                if (f < subs->freqn - (subs->freqn>>3) || f > subs->freqmax) {
-                        snd_printd(KERN_WARNING "requested frequency %d (%u,%03uHz) out of range (current nominal %d (%u,%03uHz))\n",
-                                   f, f >> 14, (f & ((1 << 14) - 1) * 1000) / ((1 << 14) - 1),
-                                   subs->freqn, subs->freqn >> 14, (subs->freqn & ((1 << 14) - 1) * 1000) / ((1 << 14) - 1));
-                        continue;
+                if (f >= subs->freqn - subs->freqn / 8 && f <= subs->freqmax) {
+                        spin_lock_irqsave(&subs->lock, flags);
+                        subs->freqm = f;
+                        spin_unlock_irqrestore(&subs->lock, flags);
                 }
-#endif
-                spin_lock_irqsave(&subs->lock, flags);
-                subs->freqm = f;
-                spin_unlock_irqrestore(&subs->lock, flags);
         }
 
         return 0;
@@ -484,9 +478,11 @@ static int retire_playback_sync_urb_hs(snd_usb_substream_t *subs,
         if (urb->iso_frame_desc[0].status == 0 &&
             urb->iso_frame_desc[0].actual_length == 4) {
                 f = combine_quad((u8*)urb->transfer_buffer) & 0x0fffffff;
-                spin_lock_irqsave(&subs->lock, flags);
-                subs->freqm = f;
-                spin_unlock_irqrestore(&subs->lock, flags);
+                if (f >= subs->freqn - subs->freqn / 8 && f <= subs->freqmax) {
+                        spin_lock_irqsave(&subs->lock, flags);
+                        subs->freqm = f;
+                        spin_unlock_irqrestore(&subs->lock, flags);
+                }
         }
 
         return 0;