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

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>

diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
index d5013383fad71dec63557b5207cc38f08ba0578c..f5aadb001986f2f9d8287686e10345f15e4e3cec 100644 (file)
--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -475,6 +475,18 @@ static int retire_playback_sync_urb_hs(struct snd_usb_substream *subs,
        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.
  *
@@ -492,16 +504,7 @@ static int prepare_startup_playback_urb(struct snd_usb_substream *subs,
        urb->dev = ctx->subs->dev;
        urb->number_of_packets = subs->packs_per_ms;
        for (i = 0; i < subs->packs_per_ms; ++i) {
-               /* 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;
-               }
+               counts = snd_usb_audio_next_packet_size(subs);
                urb->iso_frame_desc[i].offset = offs * stride;
                urb->iso_frame_desc[i].length = counts * stride;
                offs += counts;
@@ -538,16 +541,7 @@ static int prepare_playback_urb(struct snd_usb_substream *subs,
        urb->number_of_packets = 0;
        spin_lock_irqsave(&subs->lock, flags);
        for (i = 0; i < ctx->packets; i++) {
-               /* 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;
-               }
+               counts = snd_usb_audio_next_packet_size(subs);
                /* set up descriptor */
                urb->iso_frame_desc[i].offset = offs * stride;
                urb->iso_frame_desc[i].length = counts * stride;