On Thu, Apr 06, 2017 at 06:59:02PM +0200, Greg KH wrote:
> On Thu, Apr 06, 2017 at 08:11:34PM +1000, Tobin C. Harding wrote:
> > On Thu, Apr 06, 2017 at 08:08:20AM +0200, Greg KH wrote:
> > > On Thu, Apr 06, 2017 at 10:31:01AM +1000, Tobin C. Harding wrote:
> > > > Why is there code in-tree that declares generic memory addresses as
> > > > unsigned int?
> > > >
> > > > Linux Device Drivers 3rd Edition page 289
> > > > Therefore, generic memory addresses in the kernel are usually unsigned
> > > > long, exploiting the fact that pointers and long integers are always
> > > > the same size, at least on all the platforms currently supported by
> > > > Linux.
> > > >
> > > > It would therefore seem like a bug to declare a generic memory address
> > > > as an unsigned int in code that can run on 64 bit machines.
> > >
> > > I agree, that does seem like a bug.
> >
> > The example that started me looking at this is in
> > drivers/mmc/core/sdio_io.c
> >
> > int sdio_memcpy_fromio(struct sdio_func *func, void *dst,
> > unsigned int addr, int count)
> > {
> > return sdio_io_rw_ext_helper(func, 0, addr, 1, dst, count);
> > }
> >
> > Is there perhaps some reason that it can be guaranteed that this
> > address is for 32 bit architecture. Is it acceptable to think that mmc
> > cards are never more than 32 bit and this code will never have its use
> > extended to where 64 bit addresses are used?
>
> How do you know this is a "real" address, and not just an sdio
> "address"? The two are very different. See the SDIO spec for details
> about how that protocol works if you are curious.
Ok. I need to learn some more. Thanks for the tip to read the SDIO spec.
thanks,
Tobin.
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