[alsa-devel] [PATCH 1/4] ALSA: usb-audio: UAC3. Add support for mixer unit.

[Takashi Iwai]

On Fri, 20 Apr 2018 19:03:24 +0200,
Jorge Sanjuan wrote:
> 
> This adds support for the MIXER UNIT in UAC3. All the information
> is obtained from the (HIGH CAPABILITY) Cluster's header. We don't
> read the rest of the logical cluster to obtain the channel config
> as that wont make any difference in the current mixer behaviour.
> 
> The name of the mixer unit is not yet requested as there is not
> support for the UAC3 Class Specific String requests.
> 
> Tested in an UAC3 device working as a HEADSET with a basic mixer
> unit (same as the one in the BADD spec) with no controls.
> 
> Signed-off-by: Jorge Sanjuan <jorge.sanjuan at codethink.co.uk>
> ---
>  include/uapi/linux/usb/audio.h | 13 +++++++--
>  sound/usb/mixer.c              | 64 ++++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 71 insertions(+), 6 deletions(-)
> 
> diff --git a/include/uapi/linux/usb/audio.h b/include/uapi/linux/usb/audio.h
> index 3a78e7145689..f9be472cd025 100644
> --- a/include/uapi/linux/usb/audio.h
> +++ b/include/uapi/linux/usb/audio.h
> @@ -285,9 +285,16 @@ static inline __u8 uac_mixer_unit_iChannelNames(struct uac_mixer_unit_descriptor
>  static inline __u8 *uac_mixer_unit_bmControls(struct uac_mixer_unit_descriptor *desc,
>  					      int protocol)
>  {
> -	return (protocol == UAC_VERSION_1) ?
> -		&desc->baSourceID[desc->bNrInPins + 4] :
> -		&desc->baSourceID[desc->bNrInPins + 6];
> +	switch (protocol) {
> +	case UAC_VERSION_1:
> +		return &desc->baSourceID[desc->bNrInPins + 4];
> +	case UAC_VERSION_2:
> +		return &desc->baSourceID[desc->bNrInPins + 6];
> +	case UAC_VERSION_3:
> +		return &desc->baSourceID[desc->bNrInPins + 2];
> +	default:
> +		return NULL;
> +	}
>  }
>  
>  static inline __u8 uac_mixer_unit_iMixer(struct uac_mixer_unit_descriptor *desc)
> diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
> index 301ad61ed426..738ca37e6d6e 100644
> --- a/sound/usb/mixer.c
> +++ b/sound/usb/mixer.c
> @@ -719,6 +719,35 @@ static int get_term_name(struct mixer_build *state, struct usb_audio_term *iterm
>  }
>  
>  /*
> + * Get logical cluster information for UAC3 devices.
> + */
> +static int get_cluster_channels_v3(struct mixer_build *state, unsigned int cluster_id)
> +{
> +	struct uac3_cluster_header_descriptor c_header;
> +	int err;
> +
> +	err = snd_usb_ctl_msg(state->chip->dev,
> +			usb_rcvctrlpipe(state->chip->dev, 0),
> +			UAC3_CS_REQ_HIGH_CAPABILITY_DESCRIPTOR,
> +			USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN,
> +			cluster_id,
> +			snd_usb_ctrl_intf(state->chip),
> +			&c_header, sizeof(c_header));
> +	if (err < 0)
> +		goto error;
> +	else if (err != sizeof(c_header)) {
> +		err = -EIO;
> +		goto error;
> +	}

Try to balance to put braces in both if and else.
In this case, though, you can just do like below, too:

	if (err < 0)
		goto error;
	if (err != sizeof(c_header)) {
		err = -EIO;
		goto error;
	}


> +
> +	return c_header.bNrChannels;
> +
> +error:
> +	usb_audio_err(state->chip, "cannot request logical cluster ID: %d (err: %d)\n", cluster_id, err);
> +	return err;
> +}
> +
> +/*
>   * parse the source unit recursively until it reaches to a terminal
>   * or a branched unit.
>   */
> @@ -865,6 +894,19 @@ static int check_input_term(struct mixer_build *state, int id,
>  				term->name = le16_to_cpu(d->wClockSourceStr);
>  				return 0;
>  			}
> +			case UAC3_MIXER_UNIT: {
> +				struct uac_mixer_unit_descriptor *d = p1;
> +				unsigned int cluster_id = le16_to_cpu(d->baSourceID[d->bNrInPins]);
> +
> +				err = get_cluster_channels_v3(state, cluster_id);
> +				if (err < 0)
> +					return err;
> +
> +				term->channels = err;
> +				term->type = d->bDescriptorSubtype << 16; /* virtual type */
> +
> +				return 0;
> +			}
>  			default:
>  				return -ENODEV;
>  			}
> @@ -1801,7 +1843,7 @@ static void build_mixer_unit_ctl(struct mixer_build *state,
>  				 struct usb_audio_term *iterm)
>  {
>  	struct usb_mixer_elem_info *cval;
> -	unsigned int num_outs = uac_mixer_unit_bNrChannels(desc);
> +	unsigned int num_outs;
>  	unsigned int i, len;
>  	struct snd_kcontrol *kctl;
>  	const struct usbmix_name_map *map;
> @@ -1814,6 +1856,14 @@ static void build_mixer_unit_ctl(struct mixer_build *state,
>  	if (!cval)
>  		return;
>  
> +	if (state->mixer->protocol == UAC_VERSION_3) {
> +		num_outs = get_cluster_channels_v3(state,
> +				le16_to_cpu(desc->baSourceID[desc->bNrInPins]));
> +		if (num_outs < 0)
> +			return;
> +	} else /* UAC_VERSION_1/2 */
> +		num_outs = uac_mixer_unit_bNrChannels(desc);
> +
>  	snd_usb_mixer_elem_init_std(&cval->head, state->mixer, unitid);
>  	cval->control = in_ch + 1; /* based on 1 */
>  	cval->val_type = USB_MIXER_S16;
> @@ -1878,8 +1928,16 @@ static int parse_audio_mixer_unit(struct mixer_build *state, int unitid,
>  	int input_pins, num_ins, num_outs;
>  	int pin, ich, err;
>  
> -	if (desc->bLength < 11 || !(input_pins = desc->bNrInPins) ||
> -	    !(num_outs = uac_mixer_unit_bNrChannels(desc))) {
> +	if (state->mixer->protocol == UAC_VERSION_3) {
> +		err = get_cluster_channels_v3(state,
> +				le16_to_cpu(desc->baSourceID[desc->bNrInPins]));
> +		if (err < 0)
> +			return err;
> +		num_outs = err;
> +	} else /* UAC_VERSION_1/2 */
> +		num_outs = uac_mixer_unit_bNrChannels(desc);

These three calls are all similar.  Maybe it'd be cleaner if you
introduce another helper to get the channels for MU?

static int uac_mixer_unit_get_channels(struct mixer_build *state,
				struct uac_mixer_unit_descriptor *desc)
{
	int input_pins;
	int num_outs;

	if (desc->bLength < 11)
		return -EINVAL;
	input_pins = desc->bNrInPins;
	if (!input_pins)
		return -EINVAL;

	switch (state->mixer->protocol) {
	case UAC_VERSION_1:
	case UAC_VERSION_2:
	default:
		channels = uac_mixer_unit_bNrChannels(desc);
		break;
	case UAC_VERSION_3:
		channels = get_cluster_channels_v3(state, 
			le16_to_cpu(desc->baSourceID[]);
		break;
	}
	if (!channels)
		return -EINVAL;
	return channels;
}

And, as you can see in the above, you have to do the length check
before actually accessing the descriptor's field.


thanks,

Takashi