Re: [PATCH 3.2] iwlagn: fix (remove) use of PAGE_SIZE

["Guy, Wey-Yi" <wey-yi.w.guy@intel.com>]

Hi John,

On Wed, 2011-12-21 at 08:19 -0800, John W. Linville wrote:
> On Mon, Dec 19, 2011 at 02:00:59PM -0800, Wey-Yi Guy wrote:
> > From: Johannes Berg <johannes.berg@intel.com>
> > 
> > The ICT code erroneously uses PAGE_SIZE. The bug
> > is that PAGE_SIZE isn't necessarily 4096, so on
> > such platforms this code will not work correctly
> > as we'll try to attempt to read an index in the
> > table that the device never wrote, it always has
> > 4096-byte pages.
> > 
> > Additionally, the manual alignment code here is
> > unnecessary -- Documentation/DMA-API-HOWTO.txt
> > states:
> >   The cpu return address and the DMA bus master address are both
> >   guaranteed to be aligned to the smallest PAGE_SIZE order which
> >   is greater than or equal to the requested size.  This invariant
> >   exists (for example) to guarantee that if you allocate a chunk
> >   which is smaller than or equal to 64 kilobytes, the extent of the
> >   buffer you receive will not cross a 64K boundary.
> > 
> > Just use appropriate new constants and get rid of
> > the alignment code.
> > 
> > Cc: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Johannes Berg <johannes.berg@intel.com>
> > Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
> 
> This seems like a big patch.  It is a bit late in the release cycle
> to rewrite all the DMA allocation code. :-)
> 
> What platforms does this affect?  Are there actual users involved?

I understand the patch is bigger than the regular patch should be
generated for stable kernel. Johannes can explain better, but he is on
vacation. as what I understood, he work with community user who
encounter issue and root cause it is PAGE SIZE cause the problem.

Thanks
Wey