[alsa-devel] [PATCH] ALSA: usb-audio: fix PCM device order

[Tanu Kaskinen]

Ping? This patch never got any feedback, and yesterday another user
complained on PulseAudio bug tracker that Audinst HUD-mx2 doesn't work
out of the box, because by default hw:x,0 is used when hw:x,1 is the
pcm that works.

-- Tanu


On Fri, 2017-08-11 at 02:36 +0300, Alexander Tsoy wrote:
> Some cards have alternate setting with non-PCM format as the first
> altsetting in the interface descriptors. This confuses userspace, since
> alsa-lib uses device 0 by default. So lets parse interfaces in two steps:
>  1. Parse altsettings with PCM formats.
>  2. Parse altsettings with non-PCM formats.
> 
> This fixes at least following cards:
>  - Audinst HUD-mx2
>  - Audinst HUD-mini
> 
> Signed-off-by: Alexander Tsoy <alexander at tsoy.me>
> ---
>  sound/usb/stream.c | 27 ++++++++++++++++++++++++++-
>  1 file changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/sound/usb/stream.c b/sound/usb/stream.c
> index 8e9548bc1f1a..b2ebeae91396 100644
> --- a/sound/usb/stream.c
> +++ b/sound/usb/stream.c
> @@ -477,7 +477,8 @@ static struct uac2_output_terminal_descriptor *
>  	return NULL;
>  }
>  
> -int snd_usb_parse_audio_interface(struct snd_usb_audio *chip, int iface_no)
> +static int __snd_usb_parse_audio_interface(struct snd_usb_audio *chip, int iface_no,
> +				           bool *has_non_pcm, bool non_pcm)
>  {
>  	struct usb_device *dev;
>  	struct usb_interface *iface;
> @@ -634,6 +635,10 @@ int snd_usb_parse_audio_interface(struct snd_usb_audio *chip, int iface_no)
>  				iface_no, altno);
>  			continue;
>  		}
> +		if (fmt->bFormatType != UAC_FORMAT_TYPE_I)
> +			*has_non_pcm = true;
> +		if ((fmt->bFormatType == UAC_FORMAT_TYPE_I) == non_pcm)
> +			continue;
>  		if (((protocol == UAC_VERSION_1) && (fmt->bLength < 8)) ||
>  		    ((protocol == UAC_VERSION_2) && (fmt->bLength < 6))) {
>  			dev_err(&dev->dev,
> @@ -740,3 +745,23 @@ int snd_usb_parse_audio_interface(struct snd_usb_audio *chip, int iface_no)
>  	return 0;
>  }
>  
> +int snd_usb_parse_audio_interface(struct snd_usb_audio *chip, int iface_no)
> +{
> +	int err;
> +	bool has_non_pcm = false;
> +
> +	/* parse PCM formats */
> +	err = __snd_usb_parse_audio_interface(chip, iface_no, &has_non_pcm, false);
> +	if (err < 0)
> +		return err;
> +
> +	if (has_non_pcm) {
> +		/* parse non-PCM formats */
> +		err = __snd_usb_parse_audio_interface(chip, iface_no, &has_non_pcm, true);
> +		if (err < 0)
> +			return err;
> +	}
> +
> +	return 0;
> +}
> +