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

[wwguy <wey-yi.w.guy@intel.com>]

Hi John,


On Wed, 2011-12-21 at 11:58 -0800, John W. Linville wrote:
> On Wed, Dec 21, 2011 at 07:45:00AM -0800, Guy, Wey-Yi wrote:
> > 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
> 
> Unless someone screams, I'd be a lot more comfortable saving this
> for 3.3.
unless Johannes has objection, I am ok for 3.3, it is not something
people will encounter everyday on common platform..

Thanks
Wey