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[ALSA] usb-audio: factor out packet size calculation code

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Modules: USB generic driver

Move the common packet size calculation code from
prepare_startup_playback_urb() and prepare_playback_urb() to a new
function.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
This commit is contained in:
Clemens Ladisch
2006-01-12 08:19:21 +01:00
committed by Jaroslav Kysela
parent 7c79b7682e
commit 9568f461e5
1 changed files with 14 additions and 20 deletions
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34
sound/usb/usbaudio.c
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@@ -475,6 +475,18 @@ static int retire_playback_sync_urb_hs(struct snd_usb_substream *subs,
return 0; return 0;
} }
/* determine the number of frames in the next packet */
static int snd_usb_audio_next_packet_size(struct snd_usb_substream *subs)
{
if (subs->fill_max)
return subs->maxframesize;
else {
subs->phase = (subs->phase & 0xffff)
+ (subs->freqm << subs->datainterval);
return min(subs->phase >> 16, subs->maxframesize);
}
}
/* /*
* Prepare urb for streaming before playback starts. * Prepare urb for streaming before playback starts.
* *
@@ -492,16 +504,7 @@ static int prepare_startup_playback_urb(struct snd_usb_substream *subs,
urb->dev = ctx->subs->dev; urb->dev = ctx->subs->dev;
urb->number_of_packets = subs->packs_per_ms; urb->number_of_packets = subs->packs_per_ms;
for (i = 0; i < subs->packs_per_ms; ++i) { for (i = 0; i < subs->packs_per_ms; ++i) {
/* calculate the size of a packet */ counts = snd_usb_audio_next_packet_size(subs);
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].offset = offs * stride;
urb->iso_frame_desc[i].length = counts * stride; urb->iso_frame_desc[i].length = counts * stride;
offs += counts; offs += counts;
@@ -538,16 +541,7 @@ static int prepare_playback_urb(struct snd_usb_substream *subs,
urb->number_of_packets = 0; urb->number_of_packets = 0;
spin_lock_irqsave(&subs->lock, flags); spin_lock_irqsave(&subs->lock, flags);
for (i = 0; i < ctx->packets; i++) { for (i = 0; i < ctx->packets; i++) {
/* calculate the size of a packet */ counts = snd_usb_audio_next_packet_size(subs);
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;
}
/* set up descriptor */ /* set up descriptor */
urb->iso_frame_desc[i].offset = offs * stride; urb->iso_frame_desc[i].offset = offs * stride;
urb->iso_frame_desc[i].length = counts * stride; urb->iso_frame_desc[i].length = counts * stride;