[alsa-devel] [PATCH 1/5] ALSA: snd-usb: don't fail hard if mixer creation fails

[Takashi Iwai]

At Wed, 13 Jul 2011 02:13:25 +0200,
Daniel Mack wrote:
> 
> There are cards that the mixer code fails to create controls for, and
> currently, the whole sound device creation fails in such cases. This
> patch changes the code so that it just spits out warnings and continues
> looking at other functions of the descriptor set which might work just
> fine.

It depends.  If a serious error like -ENOMEM, we should abort
immediately.  It means something is really bad.

> The worst thing that can happen now is that people see soundcards that
> don't have all funcions supported, but rejecting the whole device is
> not any better.

Then it'd be better to check some "easy" errors to be ignored (or
check serious errors to abort).  I don't like ignoring all errors
blindly.


thanks,

Takashi

> 
> Signed-off-by: Daniel Mack <zonque at gmail.com>
> ---
>  sound/usb/card.c  |    5 ++---
>  sound/usb/mixer.c |    9 ++++++---
>  2 files changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/sound/usb/card.c b/sound/usb/card.c
> index 220c616..8990b49 100644
> --- a/sound/usb/card.c
> +++ b/sound/usb/card.c
> @@ -512,9 +512,8 @@ static void *snd_usb_audio_probe(struct usb_device *dev,
>  	if (err > 0) {
>  		/* create normal USB audio interfaces */
>  		if (snd_usb_create_streams(chip, ifnum) < 0 ||
> -		    snd_usb_create_mixer(chip, ifnum, ignore_ctl_error) < 0) {
> -			goto __error;
> -		}
> +		    snd_usb_create_mixer(chip, ifnum, ignore_ctl_error) < 0)
> +			snd_printk(KERN_WARNING "snd_usb_create_mixer() failed\n");
>  	}
>  
>  	/* we are allowed to call snd_card_register() many times */
> diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
> index c22fa76..c43dbea 100644
> --- a/sound/usb/mixer.c
> +++ b/sound/usb/mixer.c
> @@ -1967,7 +1967,8 @@ static int snd_usb_mixer_controls(struct usb_mixer_interface *mixer)
>  			state.oterm.name = desc->iTerminal;
>  			err = parse_audio_unit(&state, desc->bSourceID);
>  			if (err < 0)
> -				return err;
> +				snd_printk(KERN_WARNING "Unable to parse terminal with bSourceID %d\n",
> +					   desc->bSourceID);
>  		} else { /* UAC_VERSION_2 */
>  			struct uac2_output_terminal_descriptor *desc = p;
>  
> @@ -1979,12 +1980,14 @@ static int snd_usb_mixer_controls(struct usb_mixer_interface *mixer)
>  			state.oterm.name = desc->iTerminal;
>  			err = parse_audio_unit(&state, desc->bSourceID);
>  			if (err < 0)
> -				return err;
> +				snd_printk(KERN_WARNING "Unable to parse terminal with bSourceID %d\n",
> +					   desc->bSourceID);
>  
>  			/* for UAC2, use the same approach to also add the clock selectors */
>  			err = parse_audio_unit(&state, desc->bCSourceID);
>  			if (err < 0)
> -				return err;
> +				snd_printk(KERN_WARNING "Unable to parse clock terminal with bCSourceID %d\n",
> +					   desc->bCSourceID);
>  		}
>  	}
>  
> -- 
> 1.7.5.4
> 
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