On Tue, 16 Jun 2020 15:17:43 +0200,
Mark Hills wrote:
>
> +/* Update software pointer to match the hardware
> + *
> + * Return: 1 if we crossed a period threshold, otherwise 0
> + */
> +static int snd_echo_poll_substream(struct snd_pcm_substream *substream)
This is a bit confusing name. One would imagine from the function
name as if it were about the handling of poll() syscall.
> +{
> + struct snd_pcm_runtime *runtime = substream->runtime;
> + struct audiopipe *pipe = runtime->private_data;
> + unsigned counter, step, period, last_period;
> + size_t buffer_bytes;
> +
> + if (pipe->state != PIPE_STATE_STARTED)
> + return 0;
> +
> + counter = le32_to_cpu(*pipe->dma_counter);
> +
> + period = bytes_to_frames(runtime, counter)
> + / runtime->period_size;
> + last_period = bytes_to_frames(runtime, pipe->last_counter)
> + / runtime->period_size;
> +
> + if (period == last_period)
> + return 0; /* don't do any work yet */
> +
> + step = counter - pipe->last_counter;
> + pipe->last_counter = counter;
Dose this calculation consider the overlap of 32bit integer of the
counter? (I'm not sure whether the old code did it right, though.)
thanks,
Takashi
