Re: [PATCH 5/6 v2] sound: Add n64 driver

[Lauri Kasanen <cand@gmx.com>]

On Mon, 11 Jan 2021 09:05:04 +0100
Takashi Iwai <tiwai@suse.de> wrote:

> On Sun, 10 Jan 2021 18:41:46 +0100,
> Lauri Kasanen wrote:
> > It was returning nextpos, but the pointer printk was in bytes. 8192
> > bytes = 2048 frames.
>
> OK, then it must be right.
>
> Then I suppose that the update of pos should be changed in a different
> way; it should always point to the previous nextpos.  That is,
> something like:
>
> static void n64audio_push(struct n64audio_t *priv, uint8_t irq)
> {
> 	....
> 	if (irq)
> 		priv->chan.pos = priv->chan.nextpos;
> 	priv->chan.nextpos += count;
> 	priv->chan.nextpos %= priv->chan.bufsize;
>
> If we use nextpos as the position, it'll lead to the double steps at
> the first IRQ handling without snd_pcm_period_elapsed() call (the
> first step missed it), and this may confuse PCM core.

This almost works, speed is correct, but the last part is played twice.

I wonder if the first, non-irq push should just push a silent buffer,
and not update pos or nextpos at all.

- Lauri