Re: [PATCH 3/5] add sg segment limitation info to device structure

[FUJITA Tomonori <tomof@acm.org>]

On Wed, 26 Sep 2007 09:05:58 -0700
Greg KH <gregkh@suse.de> wrote:

> On Wed, Sep 26, 2007 at 05:58:01PM +0900, FUJITA Tomonori wrote:
> > iommu code merges sg segments without considering lld's sg segment
> > restrictions. iommu code can't access to the limitations because they
> > are in request_queue. This patch adds max_segment_size to device
> > structure. seg_boundary_mask will be added too later.
> > 
> > Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> > ---
> >  include/linux/device.h |    7 +++++++
> >  1 files changed, 7 insertions(+), 0 deletions(-)
> > 
> > diff --git a/include/linux/device.h b/include/linux/device.h
> > index 3a38d1f..8046b60 100644
> > --- a/include/linux/device.h
> > +++ b/include/linux/device.h
> > @@ -443,6 +443,13 @@ struct device {
> >  
> >  	struct dma_coherent_mem	*dma_mem; /* internal for coherent mem
> >  					     override */
> > +
> > +	/*
> > +	 * a low level driver may set these to teach IOMMU code about
> > +	 * sg limitations.
> > +	 */
> > +	unsigned int max_segment_size;
> 
> Does this really need to be here?  Can't it go into the bus specific
> device that needs this?

dma_map_sg() is bus specific? I think that this really need to
be. It needs to work like dma_mask in device structure.