Subject: Re: linux-next: build failure after merge of the akpm tree

From: Takashi Iwai <[email-masked]>
Date: Tue, 26 Jan 2016 22:22:14 +0100

On Tue, 26 Jan 2016 21:51:30 +0100,
Stephen Rothwell wrote:
> 
> Hi Takashi,
> 
> On Mon, 25 Jan 2016 14:45:55 +0100 Takashi Iwai <[email-masked]> wrote:
> >
> > From: Takashi Iwai <[email-masked]>
> > Subject: [PATCH v2] ALSA: compress: Disable GET_CODEC_CAPS ioctl for some
> >  architectures
> > 
> > Some architectures like PowerPC can handle the maximum struct size in
> > an ioctl only up to 13 bits, and struct snd_compr_codec_caps used by
> > SNDRV_COMPRESS_GET_CODEC_CAPS ioctl overflows this limit.  This
> > problem was revealed recently by a powerpc change, as it's now treated
> > as a fatal build error.
> > 
> > This patch is a workaround for that: for architectures with less than
> > 14 bit ioctl struct size, get rid of the handling of the relevant
> > ioctl.  We should provide an alternative equivalent ioctl code later,
> > but for now just paper over it.  Luckily, the compress API hasn't been
> > used on such architectures, so the impact must be effectively zero.
> > 
> > Signed-off-by: Takashi Iwai <[email-masked]>
> > ---
> >  sound/core/compress_offload.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> > 
> > diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
> > index 18b8dc45bb8f..0609e618107a 100644
> > --- a/sound/core/compress_offload.c
> > +++ b/sound/core/compress_offload.c
> > @@ -46,6 +46,13 @@
> >  #include <sound/compress_offload.h>
> >  #include <sound/compress_driver.h>
> >  
> > +/* FIXME: struct snd_compr_codec_caps overflows the ioctl bit size for some
> > + *        architectures, so we need to disable the relevant ioctls.
> > + */
> > +#if _IOC_SIZEBITS < 14
> > +#define COMPR_CODEC_CAPS_OVERFLOW
> > +#endif
> > +
> >  /* TODO:
> >   * - add substream support for multiple devices in case of
> >   *	SND_DYNAMIC_MINORS is not used
> > @@ -440,6 +447,7 @@ out:
> >  	return retval;
> >  }
> >  
> > +#ifndef COMPR_CODEC_CAPS_OVERFLOW
> >  static int
> >  snd_compr_get_codec_caps(struct snd_compr_stream *stream, unsigned long arg)
> >  {
> > @@ -463,6 +471,7 @@ out:
> >  	kfree(caps);
> >  	return retval;
> >  }
> > +#endif /* !COMPR_CODEC_CAPS_OVERFLOW */
> >  
> >  /* revisit this with snd_pcm_preallocate_xxx */
> >  static int snd_compr_allocate_buffer(struct snd_compr_stream *stream,
> > @@ -801,9 +810,11 @@ static long snd_compr_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
> >  	case _IOC_NR(SNDRV_COMPRESS_GET_CAPS):
> >  		retval = snd_compr_get_caps(stream, arg);
> >  		break;
> > +#ifndef COMPR_CODEC_CAPS_OVERFLOW
> >  	case _IOC_NR(SNDRV_COMPRESS_GET_CODEC_CAPS):
> >  		retval = snd_compr_get_codec_caps(stream, arg);
> >  		break;
> > +#endif
> >  	case _IOC_NR(SNDRV_COMPRESS_SET_PARAMS):
> >  		retval = snd_compr_set_params(stream, arg);
> >  		break;
> > -- 
> > 2.7.0
> 
> I have replaced my other patch in my fixes tree until someone gets this
> patch to Linus.

I've merged this to for-linus branch, so it'll be included in the next
pull request.

thanks,

Takashi