Re: [Qemu-devel] Re: [RFC][PATCH 4/4] Add support for Marvell 88w8618 / MusicPal

[malc <av1474@comtv.ru>]

On Tue, 15 Apr 2008, Jan Kiszka wrote:

> malc wrote:
>> So just leave the callback until free get's big enough, you will get
>> dropouts either way, it's just that. I guess you might also use the
>> AUD_init_time_stamp_out/AUD_get_elapsed_usec_out mechanism (implemenation
>> is right at the end of audio/audio_template.h), but i still think that
>> just going with free is saner approach.
>
> Well, took some iterations to switch my mind completely to the new
> model, but now this timestamp-free version runs as smooth as the
> previous one:

Glad to hear that.

> static void audio_callback(void *opaque, int free)
> {
> 	mv88w8618_audio_state *s = opaque;
> 	unsigned int block_size, written;
>
> 	block_size = s->threshold/2 - s->block_written;
> 	if (free - s->last_free < block_size)
> 		return;
>
> 	audio_fill_mixer_buffer(s, block_size);
> 	written = AUD_write(s->voice, s->mixer_buffer, block_size);
>
> 	s->last_free = free - written;
>
> 	if (written < block_size) {
> 		s->block_written += written;
> 		return;
> 	}
> 	s->block_written = 0;
>
> 	if (s->play_pos == 0) {
> 		s->status |= MP_AUDIO_TX_HALF;
> 		s->play_pos = s->threshold/2;
> 	} else {
> 		s->status |= MP_AUDIO_TX_FULL;
> 		s->play_pos = 0;
> 	}
>
> 	if (s->status & s->irq_enable)
> 		qemu_irq_raise(s->irq);
> }
>
> [ This would be even simpler if I could assume written == block_size ||
>  written == 0. But who knows... ]

The API has no way to enforce this, therefore the only sane option is to
assume it will happen. I confess i don't quite get the logic behind the
last_free, but as you said, it works smoothly, so be it.

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