[alsa-devel] [PATCH] ALSA: snd-usb: sample rate detection workaround for Axe-Fx II

[Daniel Mack]

On 08.09.2013 18:35, Daniel Mack wrote:
> Fractal Audio Systems Axe-Fx II and maybe other devices fail to return
> their sample rate range descriptor when only asked for the first two
> bytes.
> 
> Add a workaround and assume exactly one sample rate in this case, and
> continue with the full descriptor fetch.

Please ignore this patch for now. In an off-list discussion, it turned
out that this device needs a manual firmware download each time it is
connected, and the vendor is willing to fix that bug on the firmware
side. Hence, that issue can be fixed for all users at once, and so we
won't need that nasty workaround eventually.


Thanks,
Daniel


> 
> Signed-off-by: Daniel Mack <zonque at gmail.com>
> Reported-and-tested-by: Joachim Gahl <joachim.gahl at web.de>
> ---
>  sound/usb/format.c | 21 +++++++++++++--------
>  1 file changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/sound/usb/format.c b/sound/usb/format.c
> index 3525231..d9de43d 100644
> --- a/sound/usb/format.c
> +++ b/sound/usb/format.c
> @@ -297,13 +297,17 @@ static int parse_audio_format_rates_v2(struct snd_usb_audio *chip,
>  			      snd_usb_ctrl_intf(chip) | (clock << 8),
>  			      tmp, sizeof(tmp));
>  
> -	if (ret < 0) {
> -		snd_printk(KERN_ERR "%s(): unable to retrieve number of sample rates (clock %d)\n",
> -				__func__, clock);
> -		goto err;
> -	}
> +	/*
> +	 * Some devices, including Fractal Audio Systems Axe-Fx II, fail to
> +	 * return only a fraction of this descriptor. If that happens, assume
> +	 * we have only one sample rate and continue. In case of any other
> +	 * error, we will bail on the full descriptor fetch below.
> +	 */
> +	if (ret < 0)
> +		nr_triplets = 1;
> +	else
> +		nr_triplets = combine_word(tmp);
>  
> -	nr_triplets = (tmp[1] << 8) | tmp[0];
>  	data_size = 2 + 12 * nr_triplets;
>  	data = kzalloc(data_size, GFP_KERNEL);
>  	if (!data) {
> @@ -319,8 +323,9 @@ static int parse_audio_format_rates_v2(struct snd_usb_audio *chip,
>  			      data, data_size);
>  
>  	if (ret < 0) {
> -		snd_printk(KERN_ERR "%s(): unable to retrieve sample rate range (clock %d)\n",
> -				__func__, clock);
> +		snd_printk(KERN_ERR "%s(): unable to retrieve sample rate range "
> +				    "(clock %d, nr_triplets %d)\n",
> +				    __func__, clock, nr_triplets);
>  		ret = -EINVAL;
>  		goto err_free;
>  	}
>