Hi all,
Could I please get a sanity check on my hw_params?
I have a DMA which is providing between 1-16 channels of 4 bytes/ch worth
of data as a frame. I get an interrupt to my driver every frame's worth of
data (64 Bytes). The data is S32_LE, 16000Hz.
My DMA has 2 buffers, PING and PONG. Each receives an IRQ on a frame
length, and these local buffers are the size of a frame length (64Bytes).
#define MAX_BUFFER (64 * 2)
static struct snd_pcm_hardware my_pcm_hw =
{
.info = (SNDRV_PCM_INFO_MMAP |
SNDRV_PCM_INFO_INTERLEAVED |
SNDRV_PCM_INFO_BLOCK_TRANSFER |
SNDRV_PCM_INFO_MMAP_VALID),
.formats = SNDRV_PCM_FMTBIT_S32,
.rates = SNDRV_PCM_RATE_16000,
.rate_min = 16000,
.rate_max = 16000,
.channels_min = 1,
.channels_max = NUM_CHANNELS,
.buffer_bytes_max = MAX_BUFFER,
.period_bytes_min = 4,
.period_bytes_max = 64,
.periods_min = 2,
.periods_max = 2,
};
My understanding is that the MAX_BUFFER needs to be at least twice the size
of a period so I don't underrun. .periods_max means the maximum number of
periods in a the alsa dma_area buffer, right?
So when my DMA fires its ISR, I copy from its local PING buffer to the
dma_area at offset 0, increment the buf_pos by the frame_length (64Bytes),
and call snd_pcm_period_elapsed.
My DMA fires its ISR for its local PONG buffer, copies to the
dma_area+buf_pos, increments buf_pos (now back to 0, since buffer only
holds 2 frames/periods), and I call snd_pcm_period_elapsed again, correct?
Thanks,
Rob
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