mmap support for m25p80 device

[Brian Norris]

On Fri, Nov 20, 2015 at 09:41:52AM +0100, Philippe De Muyter wrote:
> On Thu, Nov 19, 2015 at 01:31:19PM -0800, Brian Norris wrote:
> > On Tue, Nov 17, 2015 at 06:15:03PM -0800, Brian Norris wrote:
> > > It's not quite so simple. Read the comments in mtdchar, and you'll see
> > > that there's some layering bugs that caused us to disable MMU mmap
> > > entirely. Apparently no one cared so far. Read the comments here:
> > > 
> > > commit f5cf8f07423b2677cebebcebc863af77223a4972
> > > Author: David Woodhouse <David.Woodhouse at intel.com>
> > > Date:   Tue Oct 9 15:08:10 2012 +0100
> > > 
> > >     mtd: Disable mtdchar mmap on MMU systems
> > > 
> > > But feel free to fix it.
> > 
> > I see there's an old patch that never got reviewed/tested, for doing
> > this:
> > 
> > http://patchwork.ozlabs.org/patch/327981/
> 
> I use that patch to access a battery-back-up'ed SRAM connected to the
> WEIM bus of a Freescale i.MX6q ARM processor, and it works perfectly for
> that.  On that processor, the WEIM bus maps the connected peripherals in
> the physical memory addresses range, so it is really easy to make that
> user-accessible through mmap.  Only the above patch was needed.

OK, would you mind resending it, so it can get fresh eyes?

Brian