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authorClemens Ladisch <clemens@ladisch.de>2009-01-26 08:10:19 +0100
committerTakashi Iwai <tiwai@suse.de>2009-01-26 17:05:10 +0100
commit160389c8d21c8139a93191c2e5ca2273f311ed4e (patch)
tree7be9b7c475d23343ec41b7ef0f2d97e7fffbc7b0 /sound
parent4d788e040b72d2a46ea3ba726b7fa0b65de06c88 (diff)
sound: usb-audio: make URB sizes more equal
Distribute the packets evenly among the URBs, instead of making all URBs except the last one to have the maximum size. This makes the timing of pointer updates more regular and removes some special cases from the code. Signed-off-by: Clemens Ladisch <clemens@ladisch.de> Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound')
-rw-r--r--sound/usb/usbaudio.c29
1 files changed, 5 insertions, 24 deletions
diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
index f3d4de23fed..44485b29f67 100644
--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -1035,9 +1035,9 @@ static void release_substream_urbs(struct snd_usb_substream *subs, int force)
static int init_substream_urbs(struct snd_usb_substream *subs, unsigned int period_bytes,
unsigned int rate, unsigned int frame_bits)
{
- unsigned int maxsize, n, i;
+ unsigned int maxsize, i;
int is_playback = subs->direction == SNDRV_PCM_STREAM_PLAYBACK;
- unsigned int npacks[MAX_URBS], urb_packs, total_packs, packs_per_ms;
+ unsigned int urb_packs, total_packs, packs_per_ms;
/* calculate the frequency in 16.16 format */
if (snd_usb_get_speed(subs->dev) == USB_SPEED_FULL)
@@ -1109,31 +1109,11 @@ static int init_substream_urbs(struct snd_usb_substream *subs, unsigned int peri
/* too much... */
subs->nurbs = MAX_URBS;
total_packs = MAX_URBS * urb_packs;
- }
- n = total_packs;
- for (i = 0; i < subs->nurbs; i++) {
- npacks[i] = n > urb_packs ? urb_packs : n;
- n -= urb_packs;
- }
- if (subs->nurbs <= 1) {
+ } else if (subs->nurbs < 2) {
/* too little - we need at least two packets
* to ensure contiguous playback/capture
*/
subs->nurbs = 2;
- npacks[0] = (total_packs + 1) / 2;
- npacks[1] = total_packs - npacks[0];
- } else if (npacks[subs->nurbs-1] < MIN_PACKS_URB * packs_per_ms) {
- /* the last packet is too small.. */
- if (subs->nurbs > 2) {
- /* merge to the first one */
- npacks[0] += npacks[subs->nurbs - 1];
- subs->nurbs--;
- } else {
- /* divide to two */
- subs->nurbs = 2;
- npacks[0] = (total_packs + 1) / 2;
- npacks[1] = total_packs - npacks[0];
- }
}
/* allocate and initialize data urbs */
@@ -1141,7 +1121,8 @@ static int init_substream_urbs(struct snd_usb_substream *subs, unsigned int peri
struct snd_urb_ctx *u = &subs->dataurb[i];
u->index = i;
u->subs = subs;
- u->packets = npacks[i];
+ u->packets = (i + 1) * total_packs / subs->nurbs
+ - i * total_packs / subs->nurbs;
u->buffer_size = maxsize * u->packets;
if (subs->fmt_type == USB_FORMAT_TYPE_II)
u->packets++; /* for transfer delimiter */