Commit 9568f461 authored by Clemens Ladisch's avatar Clemens Ladisch Committed by Jaroslav Kysela
Browse files

[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: default avatarClemens Ladisch <clemens@ladisch.de>
parent 7c79b768

sound/usb/usbaudio.c

+14 −20
Original line number Diff line number Diff line
@@ -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;