Re: [PATCH 3/3] echoaudio: Address bugs in the interrupt handling

[Takashi Iwai <tiwai@suse.de>]

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