Re: [Xen-devel] POSIX error names and codes in PV protocols

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Jan 26, 2017 at 07:28:44PM +0200, Oleksandr Andrushchenko wrote:
> On 01/26/2017 05:44 PM, Jan Beulich wrote:
> > > > > On 26.01.17 at 15:40, <andr2000@xxxxxxxxx> wrote:
> > > There is some work happening on new PV protocols: sndif [1],
> > > 
> > > displif [2], PV calls [3] and the common part of those is that
> > > 
> > > error/status codes must be returned as a part of a response packet.
> > > 
> > > For that Konrad suggested [1] (and Stefano already used in [3]) POSIX
> > > 
> > > to be employed here instead of defining protocol specific error codes.
> > > 
> > > The problem I see here is that POSIX only defines names of the errors,
> > > 
> > > but not values [4]. So, in order to use POSIX one still needs to define
> > > 
> > > the values (names must be the same, but values may differ for different
> > > OSes).
> > > 
> > > So, the question is what would be the best option to
> > > 
> > > a) have those numbers defined in OS agnostic way
> > > 
> > > b) have those defined for all PV protocols
> > > 
> > > Stefano has already defined the error code values in his work [3],
> > > 
> > > but for other protocols this should be reimplemented again.
> > Aren't these simply what public/errno.h provides? Why would any
> > Xen specific protocol want to define their own, now that we have
> > this base set?
> > 
> > Jan
> Indeed, thank you
> The problem is that it is not exposed to Linux, but I can see it
> in FreeBSD [1] and the helper to convert error codes [2] there as well.
> Is there any reason these are not available in Linux?

Xen error codes are Linux error codes, so I guess there's basically no need to
use them on Linux (although it would be good, just so that people is aware that
Xen and Linux are in different theoretical spaces, which happen to match in
Linux's case).

Roger.

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