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

[Anton Yakovlev]

On 26.01.2021 10:22, Guennadi Liakhovetski wrote:
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> 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@xxxxxxxxxxxxxxx>
>> ---
>> 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?

If I understood your question right, then... it's not re-counting here. :)
It's just a referencing to each channel map for each stream in one by
one manner.


>> +
>> +     /* 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;
>> +}
>
--
Anton Yakovlev
Senior Software Engineer

OpenSynergy GmbH
Rotherstr. 20, 10245 Berlin

www.opensynergy.com