This is a note to let you know that I've just added the patch titled
ALSA: snd-usb: fix calls to next_packet_size
to the 3.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
alsa-snd-usb-fix-calls-to-next_packet_size.patch
and it can be found in the queue-3.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 245baf983cc39524cce39c24d01b276e6e653c9e Mon Sep 17 00:00:00 2001
From: Daniel Mack <[email protected]>
Date: Thu, 30 Aug 2012 18:52:30 +0200
Subject: ALSA: snd-usb: fix calls to next_packet_size
From: Daniel Mack <[email protected]>
commit 245baf983cc39524cce39c24d01b276e6e653c9e upstream.
In order to support devices with implicit feedback streaming models,
packet sizes are now stored with each individual urb, and the PCM
handling code which fills the buffers purely relies on the size fields
now.
However, calling snd_usb_audio_next_packet_size() for all possible
packets in an URB at once, prior to letting the PCM code do its job
does in fact not lead to the same behaviour than what the old code did:
The PCM code will break its loop once a period boundary is reached,
consequently using up less packets that it really could.
As snd_usb_audio_next_packet_size() implements a feedback mechanism to
the endpoints phase accumulator, the number of calls to that function
matters, and when called too often, the data rate runs out of bounds.
Fix this by making the next_packet function public, and call it from the
PCM code as before if the packet data sizes are not defined.
Signed-off-by: Daniel Mack <[email protected]>
Signed-off-by: Takashi Iwai <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
sound/usb/endpoint.c | 13 +------------
sound/usb/endpoint.h | 1 +
sound/usb/pcm.c | 7 ++++++-
3 files changed, 8 insertions(+), 13 deletions(-)
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -141,7 +141,7 @@ int snd_usb_endpoint_implict_feedback_si
*
* For implicit feedback, next_packet_size() is unused.
*/
-static int next_packet_size(struct snd_usb_endpoint *ep)
+int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep)
{
unsigned long flags;
int ret;
@@ -177,15 +177,6 @@ static void retire_inbound_urb(struct sn
ep->retire_data_urb(ep->data_subs, urb);
}
-static void prepare_outbound_urb_sizes(struct snd_usb_endpoint *ep,
- struct snd_urb_ctx *ctx)
-{
- int i;
-
- for (i = 0; i < ctx->packets; ++i)
- ctx->packet_size[i] = next_packet_size(ep);
-}
-
/*
* Prepare a PLAYBACK urb for submission to the bus.
*/
@@ -370,7 +361,6 @@ static void snd_complete_urb(struct urb
goto exit_clear;
}
- prepare_outbound_urb_sizes(ep, ctx);
prepare_outbound_urb(ep, ctx);
} else {
retire_inbound_urb(ep, ctx);
@@ -857,7 +847,6 @@ int snd_usb_endpoint_start(struct snd_us
goto __error;
if (usb_pipeout(ep->pipe)) {
- prepare_outbound_urb_sizes(ep, urb->context);
prepare_outbound_urb(ep, urb->context);
} else {
prepare_inbound_urb(ep, urb->context);
--- a/sound/usb/endpoint.h
+++ b/sound/usb/endpoint.h
@@ -21,6 +21,7 @@ int snd_usb_endpoint_deactivate(struct
void snd_usb_endpoint_free(struct list_head *head);
int snd_usb_endpoint_implict_feedback_sink(struct snd_usb_endpoint *ep);
+int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep);
void snd_usb_handle_sync_urb(struct snd_usb_endpoint *ep,
struct snd_usb_endpoint *sender,
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -1029,6 +1029,7 @@ static void prepare_playback_urb(struct
struct urb *urb)
{
struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;
+ struct snd_usb_endpoint *ep = subs->data_endpoint;
struct snd_urb_ctx *ctx = urb->context;
unsigned int counts, frames, bytes;
int i, stride, period_elapsed = 0;
@@ -1040,7 +1041,11 @@ static void prepare_playback_urb(struct
urb->number_of_packets = 0;
spin_lock_irqsave(&subs->lock, flags);
for (i = 0; i < ctx->packets; i++) {
- counts = ctx->packet_size[i];
+ if (ctx->packet_size[i])
+ counts = ctx->packet_size[i];
+ else
+ counts = snd_usb_endpoint_next_packet_size(ep);
+
/* set up descriptor */
urb->iso_frame_desc[i].offset = frames * stride;
urb->iso_frame_desc[i].length = counts * stride;
Patches currently in stable-queue which might be from [email protected] are
queue-3.5/alsa-snd-usb-fix-urb-cancellation-at-stream-start.patch
queue-3.5/alsa-snd-usb-fix-calls-to-next_packet_size.patch
queue-3.5/alsa-snd-usb-fix-cross-interface-streaming-devices.patch
queue-3.5/alsa-snd-usb-restore-delay-information.patch
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