Re: [dpdk-dev] [PATCH 1/1] doc: announce change in power API

[Bruce Richardson <bruce.richardson@intel.com>]

On Fri, May 10, 2019 at 01:28:09AM +0200, Thomas Monjalon wrote:
> > > From: Marcin Hajkowski <marcinx.hajkowski@intel.com>
> > >
> > > Function rte_power_set_env will no longer return
> > > success on attempt to set env in initialized state.
> > >
> > > Signed-off-by: Marcin Hajkowski <marcinx.hajkowski@intel.com>
> > 
> > Acked-by: David Hunt <david.hunt@intel.com>
> 
> Any other comment about this deprecation notice?
> 
Seems ok to me, though the actual text is maybe a little unclear. It
implies that the function will always return -1 unless the variable is
unset when the function terminates (which seems to imply a failure case).
What I presume is meant is that we have three possibilities:

* The variable is set by the function -> return 0
* The varaible is already set, so no action needed -> return -1 (and set
  rte_errno to EEXIST or EALREADY??)
* Setting the variable failed -> return -1 (and set rte_errno to ??)

Is my understanding correct? Can the deprecation notice be improved to make
it clear that only the middle case is the one being changed, e.g. by adding
"in this case" to the second sentence. It might also be worthwhile calling
out what the errno value will be to identify this failure vs regular
failures.

/Bruce

PS: For this case, is there a reason to make it an error? Would a +1 value
not also do, so anything non-zero implies no work done, and anything >=0
means that the value is set? Call set on something already set doesn't
really seem like an error case to me.