On Thu, Aug 30, 2012 at 09:29:27PM -0700, Ben Pfaff wrote:
> On Thu, Aug 30, 2012 at 10:40:24AM +0900, Simon Horman wrote:
> > From: Isaku Yamahata <[email protected]>
> > 
> > set_field action needs more than 64 bits value unlike nx_reg_load action.
> > This is preparation for set_field action. mf_value will be used later.
> > 
> > Signed-off-by: Isaku Yamahata <[email protected]>
> > Signed-off-by: Simon Horman <[email protected]>
> 
> Presumably the goal is to make ofpact_reg_load able to set any subset of
> a field, not just a 64-bit subset.  For this, it would seem more natural
> to use union mf_subvalue instead of union mf_value.  Then
> nxm_execute_reg_load() would become a single call to
> mf_write_subfield(), rather than (as seen in patch 3/5) a conditional.

I spoke with Yamahata-san and clarified the motivation for using mf_value.

It was:
* To allow the storage of IPv6 addresses which require more than 64bits and;
* To allow use of portions of meta-flow.c

Having looked over the code I'm not convinced that it aims to set
field subsets. Do you believe that should be an aim?

> My hope here is that ofpact_reg_load can be completely uniform across
> NXAST_REG_LOAD and OFPAT12_SET_FIELD, except in the translation to and
> from OpenFlow actions.

That does sound like a good goal to me.
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