I have these lines of code:
static snd_pcm_hardware_t snd_line6_tp_ux1_playback_hw = {
.info = SNDRV_PCM_INFO_INTERLEAVED |
SNDRV_PCM_INFO_BLOCK_TRANSFER,
.formats = SNDRV_PCM_FMTBIT_S16_LE,
.rates = SNDRV_PCM_RATE_48000,
.rate_min = 48000,
.rate_max = 48000,
.channels_min = 2,
.channels_max = 2,
/* double buffering */
.buffer_bytes_max = LINE6_TP_UX1_48000_16_PACKET_SIZE_OUT * 2 * 2,
.period_bytes_min = LINE6_TP_UX1_48000_16_PACKET_SIZE_OUT * 2,
.period_bytes_max = LINE6_TP_UX1_48000_16_PACKET_SIZE_OUT * 2,
.periods_min = 1,
.periods_max = 2
};
and then also:
static snd_pcm_uframes_t snd_line6_tp_ux1_pcm_pointer (
snd_pcm_substream_t* substream)
{
struct snd_line6_tp_ux1 *chip = snd_pcm_substream_chip (substream);
printk ("pos: %d\n", chip->playback_pos);
return chip->playback_pos;
}
static int snd_line6_tp_ux1_playback_copy (snd_pcm_substream_t *substream,
int channel, snd_pcm_uframes_t pos,
void *src, snd_pcm_uframes_t count)
{
struct snd_line6_tp_ux1 *chip = snd_pcm_substream_chip (substream);
snd_pcm_runtime_t *runtime = substream->runtime;
static struct urb* urb;
int i = 0;
static int j = 0;
urb = usb_alloc_urb (2, GFP_ATOMIC);
urb->dev = chip->dev;
urb->pipe = usb_sndisocpipe (urb->dev, 1);
urb->complete = snd_line6_tp_ux1_complete_playback_transfer;
urb->context = substream;
urb->transfer_buffer = kmalloc (LINE6_TP_UX1_48000_16_PACKET_SIZE_OUT * 2, GFP_ATOMIC);
urb->transfer_buffer_length = LINE6_TP_UX1_48000_16_PACKET_SIZE_OUT * 2;
urb->transfer_flags = URB_ISO_ASAP;
memcpy (urb->transfer_buffer, src, count * 2 * 2);
for (; i < LINE6_TP_UX1_48000_16_PACKET_SIZE_OUT; i++) {
printk ("%d\n", ((s16*)urb->transfer_buffer)[i]);
}
printk ("---------\n");
urb->interval = 1;
urb->number_of_packets = 2;
urb->iso_frame_desc[0].offset = 0;
urb->iso_frame_desc[0].length = urb->iso_frame_desc[1].offset =
urb->iso_frame_desc[1].length = LINE6_TP_UX1_48000_16_PACKET_SIZE_OUT;
if (chip->playback_pos)
chip->playback_pos = 0;
else
chip->playback_pos = count;
j++;
printk (":: %d %d %d\n", j, chip->playback_pos, runtime->buffer_size);
snd_pcm_period_elapsed (substream);
usb_submit_urb (urb, GFP_KERNEL);
return count;
}
Don't care about printk()s and codying style, count in the copy callback is always 96, which is the # of frames of a period, so everytime the copy callback is called, a period is elapsed. Since the buffer is long 2 periods, the playback position pointer should be either 0 or 96, I think (beginning or half of the buffer).
Now, instead of working as expected, the copy callback just works twice, for the first two periods (one buffer length). Then the pointer becomes 0 and I can't understand why the playback stops.
Please help! I have some people who keep on asking me about the driver, and it's a pity that I can't overcome such simple problems and let them use their sound card!
Thanks,
Stefano
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