Re: [PATCH 0/5] PCM mmap (temporary) fixes for non-coherent architectures

[Takashi Iwai <tiwai@suse.de>]

At Fri, 15 Jan 2010 14:28:02 +1100,
Benjamin Herrenschmidt wrote:
> 
> 
> > A quick patch below (totally untested!) might do that.
> > It's passing the device struct blindly, so not sure whether this would
> > actually work for all dma_alloc_coherent().
> 
> On archs that have dma_ops such as powerpc (but I think x86 too
> nowadays) you cannot use the USB device for dma_* operations. You need
> to get up to the host controller device...

Yep, I don't think this being a proper fix, too.

> It -might- be worth looking at adding code to the USB stack to propagate
> the parent device dma_ops down to USB devices... hard to tell.

Or we may simply need to drop the mmap support on such architectures...


thanks,

Takashi

> 
> Cheers,
> Ben.
> 
> > 
> > Takashi
> > 
> > ---
> > diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
> > index 9edef46..6c82026 100644
> > --- a/sound/usb/usbaudio.c
> > +++ b/sound/usb/usbaudio.c
> > @@ -734,7 +734,7 @@ static void snd_complete_sync_urb(struct urb *urb)
> >  	}
> >  }
> >  
> > -
> > +#ifdef USBAUDIO_VMALLOC_BUFFER
> >  /* get the physical page pointer at the given offset */
> >  static struct page *snd_pcm_get_vmalloc_page(struct snd_pcm_substream *subs,
> >  					     unsigned long offset)
> > @@ -769,6 +769,24 @@ static int snd_pcm_free_vmalloc_buffer(struct snd_pcm_substream *subs)
> >  	return 0;
> >  }
> >  
> > +#define preallocate_buffer(chip, pcm, stream) /* NOP */
> > +
> > +#else
> > +#define snd_pcm_get_vmalloc_page	NULL
> > +#define snd_pcm_alloc_vmalloc_buffer	snd_pcm_lib_malloc_pages
> > +#define snd_pcm_free_vmalloc_buffer	snd_pcm_lib_free_pages
> > +
> > +static int preallocate_buffer(struct snd_usb_audio *chip, struct snd_pcm *pcm,
> > +			      int stream)
> > +{
> > +	struct snd_pcm_substream *subs = pcm->streams[stream].substream;
> > +	if (!subs)
> > +		return 0;
> > +	return snd_pcm_lib_preallocate_pages(subs, SNDRV_DMA_TYPE_DEV,
> > +					     chip->card->dev,
> > +					     1024 * 64, 1024 * 1024);
> > +}
> > +#endif
> >  
> >  /*
> >   * unlink active urbs.
> > @@ -2328,6 +2346,7 @@ static int add_audio_endpoint(struct snd_usb_audio *chip, int stream, struct aud
> >  		err = snd_pcm_new_stream(as->pcm, stream, 1);
> >  		if (err < 0)
> >  			return err;
> > +		preallocate_buffer(chip, as->pcm, stream);
> >  		init_substream(as, stream, fp);
> >  		return 0;
> >  	}
> > @@ -2356,6 +2375,7 @@ static int add_audio_endpoint(struct snd_usb_audio *chip, int stream, struct aud
> >  	else
> >  		strcpy(pcm->name, "USB Audio");
> >  
> > +	preallocate_buffer(chip, pcm, stream);
> >  	init_substream(as, stream, fp);
> >  
> >  	list_add(&as->list, &chip->pcm_list);
> 
>