[dpdk-dev] [PATCH v4 1/6] eventdev: introduce event driven programming model

[Richardson, Bruce]

> -----Original Message-----
> From: Eads, Gage
> Sent: Wednesday, January 25, 2017 4:32 PM
> To: Jerin Jacob <jerin.jacob at caviumnetworks.com>; dev at dpdk.org
> Cc: thomas.monjalon at 6wind.com; Richardson, Bruce
> <bruce.richardson at intel.com>; hemant.agrawal at nxp.com; Van Haaren, Harry
> <harry.van.haaren at intel.com>; McDaniel, Timothy
> <timothy.mcdaniel at intel.com>
> Subject: RE: [dpdk-dev] [PATCH v4 1/6] eventdev: introduce event driven
> programming model
> 
> Hi Jerin,
> 
> See the bottom of this email for a proposed tweak to the
> rte_event_enqueue_burst() return value.
> 
> >  -----Original Message-----
> >  From: Jerin Jacob [mailto:jerin.jacob at caviumnetworks.com]
> >  Sent: Wednesday, December 21, 2016 3:25 AM
> >  To: dev at dpdk.org
> >  Cc: thomas.monjalon at 6wind.com; Richardson, Bruce
> > <bruce.richardson at intel.com>; hemant.agrawal at nxp.com; Eads, Gage
> > <gage.eads at intel.com>; Van Haaren, Harry <harry.van.haaren at intel.com>;
> > Jerin Jacob <jerin.jacob at caviumnetworks.com>
> >  Subject: [dpdk-dev] [PATCH v4 1/6] eventdev: introduce event driven
> > programming model
> >
<message truncated for brevity>
> >  +/**
> >  + * Enqueue a burst of events objects or an event object supplied in
> >  *rte_event*
> >  + * structure on an  event device designated by its *dev_id* through
> > the event  + * port specified by *port_id*. Each event object
> > specifies the event queue on  + * which it will be enqueued.
> >  + *
> >  + * The *nb_events* parameter is the number of event objects to
> > enqueue  which are  + * supplied in the *ev* array of *rte_event*
> > structure.
> >  + *
> >  + * The rte_event_enqueue_burst() function returns the number of  + *
> > events objects it actually enqueued. A return value equal to
> > *nb_events*  + * means that all event objects have been enqueued.
> >  + *
> >  + * @param dev_id
> >  + *   The identifier of the device.
> >  + * @param port_id
> >  + *   The identifier of the event port.
> >  + * @param ev
> >  + *   Points to an array of *nb_events* objects of type *rte_event*
> structure
> >  + *   which contain the event object enqueue operations to be
> processed.
> >  + * @param nb_events
> >  + *   The number of event objects to enqueue, typically number of
> >  + *   rte_event_port_enqueue_depth() available for this port.
> >  + *
> >  + * @return
> >  + *   The number of event objects actually enqueued on the event
> device. The
> >  + *   return value can be less than the value of the *nb_events*
> parameter
> >  when
> >  + *   the event devices queue is full or if invalid parameters are
> specified in a
> >  + *   *rte_event*. If return value is less than *nb_events*, the
> remaining events
> >  + *   at the end of ev[] are not consumed,and the caller has to take
> care of
> >  them
> >  + *
> >  + * @see rte_event_port_enqueue_depth()  + */  +uint16_t
> > +rte_event_enqueue_burst(uint8_t dev_id, uint8_t port_id,
> >  +			const struct rte_event ev[], uint16_t nb_events);
> 
> There are a number of reasons this operation could fail to enqueue all the
> events, including:
> - Backpressure
> - Invalid port ID
> - Invalid queue ID
> - Invalid sched type when a queue is configured for ATOMIC_ONLY,
> ORDERED_ONLY, or PARALLEL_ONLY
> - ...
> 
> The current API doesn't provide a straightforward way to determine the
> cause of a failure. This is a particular issue on event PMDs that can
> backpressure, where the app may want to treat that case differently than
> the other failure cases.
> 
> Could we change the return type to int16_t, and define a set of error
> cases (e.g. -ENOSPC for backpressure, -EINVAL for an invalid argument)?
> (With corresponding changes needed in the PMD API) Similarly we could
> change rte_event_dequeue_burst() to return an int16_t, with -EINVAL as a
> possible error case.

Use rte_errno instead, I suggest. That's what it's there for.

/Bruce