Re: [PATCH 25/25] rte_eal_init: add info about rte_errno codes

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

On Fri, Jan 27, 2017 at 08:33:46AM -0800, Stephen Hemminger wrote:
> On Fri, 27 Jan 2017 09:57:03 -0500
> Aaron Conole <aconole@redhat.com> wrote:
> 
> > diff --git a/lib/librte_eal/common/include/rte_eal.h b/lib/librte_eal/common/include/rte_eal.h
> > index 03fee50..46e427f 100644
> > --- a/lib/librte_eal/common/include/rte_eal.h
> > +++ b/lib/librte_eal/common/include/rte_eal.h
> > @@ -159,7 +159,29 @@ int rte_eal_iopl_init(void);
> >   *     function call and should not be further interpreted by the
> >   *     application.  The EAL does not take any ownership of the memory used
> >   *     for either the argv array, or its members.
> > - *   - On failure, a negative error value.
> > + *   - On failure, -1 and rte_errno is set to a value indicating the cause
> > + *     for failure.
> > + *
> > + *   The error codes returned via rte_errno:
> > + *     EACCES indicates a permissions issue.
> > + *
> > + *     EAGAIN indicates either a bus or system resource was not available,
> > + *            try again.
> > + *
> > + *     EALREADY indicates that the rte_eal_init function has already been
> > + *              called, and cannot be called again.
> > + *
> > + *     EINVAL indicates invalid parameters were passed as argv/argc.
> > + *
> > + *     EIO indicates failure to setup the logging handlers.  This is usually
> > + *         caused by an out-of-memory condition.
> > + *
> > + *     ENODEV indicates memory setup issues.
> > + *
> > + *     ENOTSUP indicates that the EAL cannot initialize on this system.
> > + *
> > + *     EUNATCH indicates that the PCI bus is either not present, or is not
> > + *             readable by the eal.
> >   */
> >  int rte_eal_init(int argc, char **argv);
> 
> Why use rte_errno?
> Most DPDK calls just return negative value on error which corresponds to error number.
> Are you trying to keep ABI compatibility? Doesn't make sense because before all these
> errors were panic's no working application is going to care.

Either will work, but I actually prefer this way. I view using rte_errno
to be better as it can work in just about all cases, including with
functions which return pointers. This allows you to have a standard
method across all functions for returning error codes, and it only
requires a single sentinal value to indicate error, rather than using a
whole range of values.

/Bruce