[PATCH] uapi: fix linux/usb/audio.h userspace compilation error

[PATCH] uapi: fix linux/usb/audio.h userspace compilation error

[Dmitry V. Levin]

Replace NULL with 0 in uac_mixer_unit_bmControls() to fix the following
linux/usb/audio.h userspace compilation error:

/usr/include/linux/usb/audio.h: In function 'uac_mixer_unit_bmControls':
/usr/include/linux/usb/audio.h:304:10: error: 'NULL' undeclared (first use in this function)
   return NULL;

Fixes: 6cfd839ae78e ("ALSA: usb-audio: UAC3. Add support for mixer unit.")
Cc: <stable@vger.kernel.org> # v4.18
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
---
 include/uapi/linux/usb/audio.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/usb/audio.h b/include/uapi/linux/usb/audio.h
index 74e520fb944f..2b61fe34b2ca 100644
--- a/include/uapi/linux/usb/audio.h
+++ b/include/uapi/linux/usb/audio.h
@@ -301,7 +301,7 @@ static inline __u8 *uac_mixer_unit_bmControls(struct uac_mixer_unit_descriptor *
 	case UAC_VERSION_3:
 		return &desc->baSourceID[desc->bNrInPins + 2];
 	default:
-		return NULL;
+		return 0;
 	}
 }
 
-- 
ldv

Re: [PATCH] uapi: fix linux/usb/audio.h userspace compilation error

[Takashi Iwai]

On Mon, 13 Aug 2018 17:46:51 +0200,
Dmitry V. Levin wrote:
> 
> Replace NULL with 0 in uac_mixer_unit_bmControls() to fix the following
> linux/usb/audio.h userspace compilation error:
> 
> /usr/include/linux/usb/audio.h: In function 'uac_mixer_unit_bmControls':
> /usr/include/linux/usb/audio.h:304:10: error: 'NULL' undeclared (first use in this function)
>    return NULL;
> 
> Fixes: 6cfd839ae78e ("ALSA: usb-audio: UAC3. Add support for mixer unit.")
> Cc: <stable@vger.kernel.org> # v4.18
> Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>

Hrm, can we include the standard header for definition of NULL
instead?  It's way too ugly to use 0 just for that.


thanks,

Takashi

> ---
>  include/uapi/linux/usb/audio.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/uapi/linux/usb/audio.h b/include/uapi/linux/usb/audio.h
> index 74e520fb944f..2b61fe34b2ca 100644
> --- a/include/uapi/linux/usb/audio.h
> +++ b/include/uapi/linux/usb/audio.h
> @@ -301,7 +301,7 @@ static inline __u8 *uac_mixer_unit_bmControls(struct uac_mixer_unit_descriptor *
>  	case UAC_VERSION_3:
>  		return &desc->baSourceID[desc->bNrInPins + 2];
>  	default:
> -		return NULL;
> +		return 0;
>  	}
>  }
>  
> -- 
> ldv
> 

Re: [PATCH] uapi: fix linux/usb/audio.h userspace compilation error

[Dmitry V. Levin]

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On Mon, Aug 13, 2018 at 05:55:25PM +0200, Takashi Iwai wrote:
> On Mon, 13 Aug 2018 17:46:51 +0200, Dmitry V. Levin wrote:
> > 
> > Replace NULL with 0 in uac_mixer_unit_bmControls() to fix the following
> > linux/usb/audio.h userspace compilation error:
> > 
> > /usr/include/linux/usb/audio.h: In function 'uac_mixer_unit_bmControls':
> > /usr/include/linux/usb/audio.h:304:10: error: 'NULL' undeclared (first use in this function)
> >    return NULL;
> > 
> > Fixes: 6cfd839ae78e ("ALSA: usb-audio: UAC3. Add support for mixer unit.")
> > Cc: <stable@vger.kernel.org> # v4.18
> > Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
> 
> Hrm, can we include the standard header for definition of NULL
> instead?  It's way too ugly to use 0 just for that.

It's fine to return 0 as a null pointer.  If you prefer NULL,
please include a header that won't break userspace,
or just move the function out of UAPI.

Thanks,


-- 
ldv

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Re: [PATCH] uapi: fix linux/usb/audio.h userspace compilation error

[Takashi Iwai]

On Mon, 13 Aug 2018 18:01:06 +0200,
Dmitry V. Levin wrote:
> 
> On Mon, Aug 13, 2018 at 05:55:25PM +0200, Takashi Iwai wrote:
> > On Mon, 13 Aug 2018 17:46:51 +0200, Dmitry V. Levin wrote:
> > > 
> > > Replace NULL with 0 in uac_mixer_unit_bmControls() to fix the following
> > > linux/usb/audio.h userspace compilation error:
> > > 
> > > /usr/include/linux/usb/audio.h: In function 'uac_mixer_unit_bmControls':
> > > /usr/include/linux/usb/audio.h:304:10: error: 'NULL' undeclared (first use in this function)
> > >    return NULL;
> > > 
> > > Fixes: 6cfd839ae78e ("ALSA: usb-audio: UAC3. Add support for mixer unit.")
> > > Cc: <stable@vger.kernel.org> # v4.18
> > > Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
> > 
> > Hrm, can we include the standard header for definition of NULL
> > instead?  It's way too ugly to use 0 just for that.
> 
> It's fine to return 0 as a null pointer.

Fine from syntax POV, but not from semantic.

> If you prefer NULL,
> please include a header that won't break userspace,
> or just move the function out of UAPI.

Maybe better to remove the function from uapi, then.


Takashi