Re: [PATCH RFC 2/3] x86-64: Calgary IOMMU - Calgary specific bits

[Olof Johansson]

On Tue, Mar 14, 2006 at 07:27:33PM -0600, Jon Mason wrote:

> > We're killing structures like that one by one on PPC, I just haven't
> > gotten around to dealing with tce_entry yet.
> > 
> > The way to do it is to use masking and shifting by hand.
> 
> Really?  I thought this was much more elegant than masking and
> bitshifting (and less prone to errors).  Is there a particular reason to
> do it that way?

Me too, but what I've been told is that there's no guarantee for the
union/struct layouts being exactly like you (and the hardware) expects
them to be across toolchains, etc.

The endianness issues are also painful, in architecture-specific code it's
obviously not as big an issue as in generic drivers. Single-architecture
system drivers are a grey area in that aspect, but it's better to set
good examples then bad ones for the generic driver writers looking for
example code.


-Olof
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/