2.6.15.2 -stable review patch. If anyone has any objections, please let
us know.
------------------
From: Clemens Ladisch <[email protected]>
Some widespread USB interface chips with adaptive iso endpoints hang
after receiving a series of empty packets when they expect data. This
completely disables audio playback on those devices. To avoid this, we
have to send packets containing silence (zero samples) instead.
ALSA bug: http://bugtrack.alsa-project.org/alsa-bug/view.php?id=1585
Signed-off-by: Clemens Ladisch <[email protected]>
Signed-off-by: Chris Wright <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
sound/usb/usbaudio.c | 26 +++++++++++++++++++++-----
1 file changed, 21 insertions(+), 5 deletions(-)
--- linux-2.6.15.1.orig/sound/usb/usbaudio.c
+++ linux-2.6.15.1/sound/usb/usbaudio.c
@@ -480,22 +480,38 @@ static int retire_playback_sync_urb_hs(s
/*
* Prepare urb for streaming before playback starts.
*
- * We don't care about (or have) any data, so we just send a transfer delimiter.
+ * We don't yet have data, so we send a frame of silence.
*/
static int prepare_startup_playback_urb(snd_usb_substream_t *subs,
snd_pcm_runtime_t *runtime,
struct urb *urb)
{
- unsigned int i;
+ unsigned int i, offs, counts;
snd_urb_ctx_t *ctx = urb->context;
+ int stride = runtime->frame_bits >> 3;
+ offs = 0;
urb->dev = ctx->subs->dev;
urb->number_of_packets = subs->packs_per_ms;
for (i = 0; i < subs->packs_per_ms; ++i) {
- urb->iso_frame_desc[i].offset = 0;
- urb->iso_frame_desc[i].length = 0;
+ /* calculate the size of a packet */
+ if (subs->fill_max)
+ counts = subs->maxframesize; /* fixed */
+ else {
+ subs->phase = (subs->phase & 0xffff)
+ + (subs->freqm << subs->datainterval);
+ counts = subs->phase >> 16;
+ if (counts > subs->maxframesize)
+ counts = subs->maxframesize;
+ }
+ urb->iso_frame_desc[i].offset = offs * stride;
+ urb->iso_frame_desc[i].length = counts * stride;
+ offs += counts;
}
- urb->transfer_buffer_length = 0;
+ urb->transfer_buffer_length = offs * stride;
+ memset(urb->transfer_buffer,
+ subs->cur_audiofmt->format == SNDRV_PCM_FORMAT_U8 ? 0x80 : 0,
+ offs * stride);
return 0;
}
--
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
