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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 21:43:40
Message-ID: Pine.LNX.4.61.0410181740300.4038 () xanadu ! home
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On Mon, 18 Oct 2004, Marc Singer wrote:

> On Mon, Oct 18, 2004 at 10:11:26PM +0100, Russell King - ARM Linux wrote:
> > On Mon, Oct 18, 2004 at 12:34:45PM -0700, 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.
> > > 
> > > I think that my options are
> > > 
> > >   1) ignore the problem and create a custom maps driver with NO_XIP set.
> > >   2) create a custom maps driver, but use the io_table_init mechanism
> > >      to map the memory contiguously (eeww)
> > >   3) find a clever method to do something like this
> > > 
> > >      struct memvec mv = { { PHYS0, LEN0 }, {PHYS1, LEN1 } };
> > >      void* virt = ioremapv (memvec, 2);
> > 
> > 4) use the mtdconcat driver, just like the SA1100 map driver does.
> 
> Looking at mtdconcat: that's a HUGE amount of code when the same can
> be solved with a linear memory mapping.

mtdconcat is meant to be generic.

Anyway, even if your combined flash chips are mapped contiguous, the MTD 
code will still detect 2 different MTD devices anyway, right?  So you 
can't access both just as if they were one larger physical chip simply 
by mapping them contiguously.


Nicolas

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