[dpdk-dev] Bulk dequeue of packets and the returned values, question

[Neil Horman]

On Sun, Sep 28, 2014 at 03:23:44PM -0700, Venkatesan, Venky wrote:
> Keith,
> 
> On 9/28/2014 11:04 AM, Wiles, Roger Keith wrote:
> >I am also looking at the bulk dequeue routines, which the ring can be fixed or variable. On fixed  < 0 on error is returned and 0 if successful. On a variable ring < 0 on error or n on success, but I think n can be zero in the variable case, correct?
> >
> >If these are true then why not have the routines return  < 0 on error and >= 0 on success. Which means a dequeue from a fixed ring would return only ’requested size n’ or < 0 if you error off the 0 case. The 0 case could be OK, if you allow zero to be return on a empty ring for the fixed ring case.
> >
> >Does this make sense to anyone?
> It won't make sense unless you're aware of the history behind these
> functions. The original functions that were implemented for the ring were
> only the bulk functions (i.e. FIXED). They would return exactly the number
> of items requested for dequeue (0 if success, negative if error), and not
> return any if the required number were not available.
> 
> The burst (i.e. VARIABLE) functions came in much later (think it was r1.3
> where we introduced them), and by that time, there were already quite a
> number of deployments of DPDK in the field using the legacy ring functions.
> Therefore we made the decision to keep the legacy behavior intact & not
> impacting deployed code - and merging the burst functions into the code.
> Given that there was no "versioning" of the API/ABI in those releases :).
> 
Hehe :)

Yes, API versioning would be a great benefit to this sort of problem.  If only
there were a patchset available to create that ability ;)

Neil