Re: [PATCH v2 8/9] ALSA: virtio: introduce PCM channel map support

[Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>]

On Sun, 24 Jan 2021, Anton Yakovlev wrote:

> Enumerate all available PCM channel maps and create ALSA controls.
>
> Signed-off-by: Anton Yakovlev <anton.yakovlev@opensynergy.com>
> ---
> sound/virtio/Makefile       |   1 +
> sound/virtio/virtio_card.c  |  15 +++
> sound/virtio/virtio_card.h  |   8 ++
> sound/virtio/virtio_chmap.c | 237 ++++++++++++++++++++++++++++++++++++
> sound/virtio/virtio_pcm.h   |   4 +
> 5 files changed, 265 insertions(+)
> create mode 100644 sound/virtio/virtio_chmap.c

[snip]

> diff --git a/sound/virtio/virtio_chmap.c b/sound/virtio/virtio_chmap.c
> new file mode 100644
> index 000000000000..8a2ddc4dcffb
> --- /dev/null
> +++ b/sound/virtio/virtio_chmap.c
> @@ -0,0 +1,237 @@

[snip]

> +/**
> + * virtsnd_chmap_parse_cfg() - Parse the channel map configuration.
> + * @snd: VirtIO sound device.
> + *
> + * This function is called during initial device initialization.
> + *
> + * Context: Any context that permits to sleep.
> + * Return: 0 on success, -errno on failure.
> + */
> +int virtsnd_chmap_parse_cfg(struct virtio_snd *snd)
> +{
> +	struct virtio_device *vdev = snd->vdev;
> +	unsigned int i;
> +	int rc;
> +
> +	virtio_cread(vdev, struct virtio_snd_config, chmaps, &snd->nchmaps);
> +	if (!snd->nchmaps)
> +		return 0;
> +
> +	snd->chmaps = devm_kcalloc(&vdev->dev, snd->nchmaps,
> +				   sizeof(*snd->chmaps), GFP_KERNEL);
> +	if (!snd->chmaps)
> +		return -ENOMEM;
> +
> +	rc = virtsnd_ctl_query_info(snd, VIRTIO_SND_R_CHMAP_INFO, 0,
> +				    snd->nchmaps, sizeof(*snd->chmaps),
> +				    snd->chmaps);
> +	if (rc)
> +		return rc;
> +
> +	/* Count the number of channel maps per each PCM device/stream. */
> +	for (i = 0; i < snd->nchmaps; ++i) {
> +		struct virtio_snd_chmap_info *info = &snd->chmaps[i];
> +		unsigned int nid = le32_to_cpu(info->hdr.hda_fn_nid);
> +		struct virtio_pcm *pcm;
> +		struct virtio_pcm_stream *stream;
> +
> +		pcm = virtsnd_pcm_find_or_create(snd, nid);
> +		if (IS_ERR(pcm))
> +			return PTR_ERR(pcm);
> +
> +		switch (info->direction) {
> +		case VIRTIO_SND_D_OUTPUT: {
> +			stream = &pcm->streams[SNDRV_PCM_STREAM_PLAYBACK];
> +			break;
> +		}
> +		case VIRTIO_SND_D_INPUT: {
> +			stream = &pcm->streams[SNDRV_PCM_STREAM_CAPTURE];
> +			break;
> +		}
> +		default: {
> +			dev_err(&vdev->dev,
> +				"chmap #%u: unknown direction (%u)\n", i,
> +				info->direction);
> +			return -EINVAL;
> +		}
> +		}
> +
> +		stream->nchmaps++;
> +	}
> +
> +	return 0;
> +}
> +
> +/**
> + * virtsnd_chmap_add_ctls() - Create an ALSA control for channel maps.
> + * @pcm: ALSA PCM device.
> + * @direction: PCM stream direction (SNDRV_PCM_STREAM_XXX).
> + * @stream: VirtIO PCM stream.
> + *
> + * Context: Any context.
> + * Return: 0 on success, -errno on failure.
> + */
> +static int virtsnd_chmap_add_ctls(struct snd_pcm *pcm, int direction,
> +				  struct virtio_pcm_stream *stream)
> +{
> +	unsigned int i;
> +	int max_channels = 0;
> +
> +	for (i = 0; i < stream->nchmaps; i++)
> +		if (max_channels < stream->chmaps[i].channels)
> +			max_channels = stream->chmaps[i].channels;
> +
> +	return snd_pcm_add_chmap_ctls(pcm, direction, stream->chmaps,
> +				      max_channels, 0, NULL);
> +}
> +
> +/**
> + * virtsnd_chmap_build_devs() - Build ALSA controls for channel maps.
> + * @snd: VirtIO sound device.
> + *
> + * Context: Any context.
> + * Return: 0 on success, -errno on failure.
> + */
> +int virtsnd_chmap_build_devs(struct virtio_snd *snd)
> +{
> +	struct virtio_device *vdev = snd->vdev;
> +	struct virtio_pcm *pcm;
> +	struct virtio_pcm_stream *stream;
> +	unsigned int i;
> +	int rc;
> +
> +	/* Allocate channel map elements per each PCM device/stream. */
> +	list_for_each_entry(pcm, &snd->pcm_list, list) {
> +		for (i = 0; i < ARRAY_SIZE(pcm->streams); ++i) {
> +			stream = &pcm->streams[i];
> +
> +			if (!stream->nchmaps)
> +				continue;
> +
> +			stream->chmaps = devm_kcalloc(&vdev->dev,
> +						      stream->nchmaps + 1,
> +						      sizeof(*stream->chmaps),
> +						      GFP_KERNEL);
> +			if (!stream->chmaps)
> +				return -ENOMEM;
> +
> +			stream->nchmaps = 0;
> +		}
> +	}
> +
> +	/* Initialize channel maps per each PCM device/stream. */
> +	for (i = 0; i < snd->nchmaps; ++i) {
> +		struct virtio_snd_chmap_info *info = &snd->chmaps[i];
> +		unsigned int nid = le32_to_cpu(info->hdr.hda_fn_nid);
> +		unsigned int channels = info->channels;
> +		unsigned int ch;
> +		struct snd_pcm_chmap_elem *chmap;
> +
> +		pcm = virtsnd_pcm_find(snd, nid);
> +		if (IS_ERR(pcm))
> +			return PTR_ERR(pcm);
> +
> +		if (info->direction == VIRTIO_SND_D_OUTPUT)
> +			stream = &pcm->streams[SNDRV_PCM_STREAM_PLAYBACK];
> +		else
> +			stream = &pcm->streams[SNDRV_PCM_STREAM_CAPTURE];
> +
> +		chmap = &stream->chmaps[stream->nchmaps++];
> +
> +		if (channels > ARRAY_SIZE(chmap->map))
> +			channels = ARRAY_SIZE(chmap->map);
> +
> +		chmap->channels = channels;
> +
> +		for (ch = 0; ch < channels; ++ch) {
> +			u8 position = info->positions[ch];
> +
> +			if (position >= ARRAY_SIZE(g_v2a_position_map))
> +				return -EINVAL;
> +
> +			chmap->map[ch] = g_v2a_position_map[position];
> +		}
> +	}

You enter this function after virtsnd_chmap_parse_cfg() has run. And 
virtsnd_chmap_parse_cfg() has already found or created all the PCMs and 
counted channel maps - the same way as you do in the above loop. Wouldn't 
it be enough to reuse the result of that counting and avoid re-counting 
here?

> +
> +	/* Create an ALSA control per each PCM device/stream. */
> +	list_for_each_entry(pcm, &snd->pcm_list, list) {
> +		if (!pcm->pcm)
> +			continue;
> +
> +		for (i = 0; i < ARRAY_SIZE(pcm->streams); ++i) {
> +			stream = &pcm->streams[i];
> +
> +			if (!stream->nchmaps)
> +				continue;
> +
> +			rc = virtsnd_chmap_add_ctls(pcm->pcm, i, stream);
> +			if (rc)
> +				return rc;
> +		}
> +	}
> +
> +	return 0;
> +}