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List:       linux-arm-kernel
Subject:    Re: ioremap non-contiguous phys to contiguous virt?
From:       Nicolas Pitre <nico () cam ! org>
Date:       2004-10-18 21:39:23
Message-ID: Pine.LNX.4.61.0410181734230.4038 () xanadu ! home
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On Mon, 18 Oct 2004, Marc Singer wrote:

> On Mon, Oct 18, 2004 at 05:06:45PM -0400, Nicolas Pitre wrote:
> > On Mon, 18 Oct 2004, Marc Singer wrote:
> > 
> > > For the sake of the making it easy on the mtd drivers, I'd like to map
> > > discontiguous physical memory to a contiguous virtual address space.
> > > This hardware layout is an artifact of the design that allows a larger
> > > flash device to be used in later implementations.
> > 
> > You mean that the same flash gets split apart in the physical space?
> 
> Well, to tell the truth, yes.  This flash part is really two 64MiB
> devices in one package.  There is a bank select line (the BS line ;-)
> ) that enables the bank.  It could be thought of as the highest order
> address line, but that isn't how it is wired.

Ha....  Thanks for clarifying.

But why didn't they just make a single device with twice the capacity???
Oh well...

> The designer left room
> for a larger device to be soldered in without laying out another
> board.

Sensible.  Then hte current official way is actually to use mtdconcat.

> It looks like an __ioremapv could be written without too much grief.  
> Is there a reason why this would be a bad idea?

The fact that you might be the only one to use it.


Nicolas

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