Re: [Xen-devel] [PATCH v1 2/8] xen/arm: io: Extend write/read handler to pass the register in parameter

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Mon, 2015-09-28 at 17:35 +0100, Julien Grall wrote:
> Hi Ian,
> 
> On 25/09/15 17:36, Ian Campbell wrote:
> > On Fri, 2015-09-25 at 15:51 +0100, Julien Grall wrote:
> > > From: Julien Grall <julien.grall@xxxxxxxxxx>
> > > 
> > > Rather than letting each handler to retrieve the register used by the
> > > I/O access, add a new parameter to pass the register in parameter.
> > > 
> > > This will help to implement generic register manipulation on I/O
> > > access
> > > such as sign-extension and endianess.
> > > 
> > > Read handlers need to modify the value of the register, so a pointer
> > > to
> > > it is given in argument. Write handlers shouldn't modify the
> > > register,
> > > therfore only a plain value is given.
> > 
> > "therefore"
> > > 
> > > Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> > 
> > Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxxx
> > 
> > Is it the case that read handlers today only update *r on success? 
> 
> Yes, each read handler only update the register mentioned in dabt.reg.

I meant that they do not touch it on failure.

> > Is that
> > a useful thing to mandate and/or enforce?
> 
> What do you mean?
> 
> Regards,
> 

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