Re: [PATCH 00/03][RFC] Reusable UIO Platform Driver

From: Uwe Kleine-König
Date: Wed May 21 2008 - 04:06:12 EST

Paul Mundt wrote:
> On Wed, May 21, 2008 at 08:49:38AM +0200, Uwe Kleine-K?nig wrote:
> > Magnus Damm wrote:
> > > Extending uio_pdrv driver with a chunk of physically
> > > contiguous memory isn't a big deal though.
> > I wonder how you use that memory. Isn't it just some kind of shared
> > memory? If so, why not use normal shared memory? Do you really need
> > that?
> >
> Physically contiguous memory is a real requirement, especially for DMA.
> I'm not sure what's confusing about that?
I got that, yes. The problem is I don't see how you can use it for DMA.
The physical address is stored in info->mem[$last].internal_addr and if
there is a way to access that variable from user space, I don't see it
and would appretiate a hint. Sorry for not expressing my concern more
clear at the first go. I hope it's understandable now.

@Magnus: Maybe you can provide the userspace part of the driver?
How is that mapping used there?

Best regards

Uwe Kleine-König, Software Engineer
Digi International GmbH Branch Breisach, Küferstrasse 8, 79206 Breisach, Germany
Tax: 315/5781/0242 / VAT: DE153662976 / Reg. Amtsgericht Dortmund HRB 13962
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