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[ALSA] usb-audio: optimize handling of capture URBs 

USB generic driver
When preparing capture URBs, we don't need to stop when we cross a
period boundary because we now never handle more than one millisecond of
data per URB anyway.

When handling captured data, use an extra flag to call
snd_pcm_period_elapsed() no more than once.  This allows us to move the
period boundary checking code before the copying of the data which
avoids a second locking of the substream's lock.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
This commit is contained in:
Clemens Ladisch 2005-08-15 08:22:39 +02:00 committed by Jaroslav Kysela
parent 99250872fc
commit b263a9bdf9
1 changed files with 8 additions and 18 deletions
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26
sound/usb/usbaudio.c
View File

@ -311,27 +311,18 @@ static int prepare_capture_urb(snd_usb_substream_t *subs,
struct urb *urb)
{
int i, offs;
unsigned long flags;
snd_urb_ctx_t *ctx = (snd_urb_ctx_t *)urb->context;
offs = 0;
urb->dev = ctx->subs->dev; /* we need to set this at each time */
urb->number_of_packets = 0;
spin_lock_irqsave(&subs->lock, flags);
for (i = 0; i < ctx->packets; i++) {
urb->iso_frame_desc[i].offset = offs;
urb->iso_frame_desc[i].length = subs->curpacksize;
offs += subs->curpacksize;
urb->number_of_packets++;
subs->transfer_sched += subs->curframesize;
if (subs->transfer_sched >= runtime->period_size) {
subs->transfer_sched -= runtime->period_size;
break;
}
}
spin_unlock_irqrestore(&subs->lock, flags);
urb->transfer_buffer = ctx->buf;
urb->transfer_buffer_length = offs;
urb->number_of_packets = ctx->packets;
#if 0 // for check
if (! urb->bandwidth) {
int bustime;
@ -359,6 +350,7 @@ static int retire_capture_urb(snd_usb_substream_t *subs,
unsigned char *cp;
int i;
unsigned int stride, len, oldptr;
int period_elapsed = 0;
stride = runtime->frame_bits >> 3;
@ -378,6 +370,10 @@ static int retire_capture_urb(snd_usb_substream_t *subs,
if (subs->hwptr_done >= runtime->buffer_size)
subs->hwptr_done -= runtime->buffer_size;
subs->transfer_done += len;
if (subs->transfer_done >= runtime->period_size) {
subs->transfer_done -= runtime->period_size;
period_elapsed = 1;
}
spin_unlock_irqrestore(&subs->lock, flags);
/* copy a data chunk */
if (oldptr + len > runtime->buffer_size) {
@ -388,15 +384,9 @@ static int retire_capture_urb(snd_usb_substream_t *subs,
} else {
memcpy(runtime->dma_area + oldptr * stride, cp, len * stride);
}
/* update the pointer, call callback if necessary */
spin_lock_irqsave(&subs->lock, flags);
if (subs->transfer_done >= runtime->period_size) {
subs->transfer_done -= runtime->period_size;
spin_unlock_irqrestore(&subs->lock, flags);
snd_pcm_period_elapsed(subs->pcm_substream);
} else
spin_unlock_irqrestore(&subs->lock, flags);
}
if (period_elapsed)
snd_pcm_period_elapsed(subs->pcm_substream);
return 0;
}