Re: UIO support for >32-bit physical addresses on 32-bit platforms

["Hans J. Koch" <hjk@linutronix.de>]

On Tue, Feb 23, 2010 at 09:24:42PM -0600, Kumar Gala wrote:
> > Well, UIO is (up to now) completely independent of the architecture. If you've
> > got a good idea how to implement such mappings, feel free to come up with your
> > suggestions/patches. Just changing struct uio_mem.addr to u64 is certainly not
> > enough.
> > 
> > I'll give it some thoughts myself, and will discuss the problem with friends,
> > maybe there's a nice solution. Help from your side is much appreciated.
> 
> For my needs I believe changing uio_mem.addr to a u64 is sufficient for getting UIO_MEM_PHYS to work for the physical address being above 4G.  I need the type to be large to represent a wider PFN range.  Obviously there are limitations (ie, we can't make an IO region >4G in size, etc.)
> 

Hmm, after some research it seems you're right. But the type for the addr
member of struct uio_mem should be phys_addr_t, not u64. phys_addr_t is
an u64 on systems that support it, and an u32 otherwise.

It'll probably work with UIO_MEM_LOGICAL and UIO_MEM_VIRTUAL as well.

Could you hack up a patch to that effect, and test it? If it works for you,
I think we should apply it.

Thanks for pointing this out.

Hans

> - k