Re: [dpdk-dev] [PATCH] ethdev: additional parameter in RX callback

["Mcnamara, John" <john.mcnamara@intel.com>]

> -----Original Message-----
> From: Neil Horman [mailto:nhorman@tuxdriver.com]
> Sent: Friday, March 13, 2015 5:32 PM
> To: Mcnamara, John
> Cc: Richardson, Bruce; dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] ethdev: additional parameter in RX
> callback
> 
> > Is encoding the information in the array really a better solution here?
> The cb->param already exists for passing in user defined information to
> the callback. The proposed patch merely transmits the parent function
> arguments to the enclosed callback.
> >
> The cb->param can't be used here, because its opaque to the internals of
> the DPDK.  rte_eth_rx_burst doesn't (and can't) know where in the cb-
> >params pointer to store that information.  Thats why you added an
> additional parameter in the first place, isn't it?

Yes. That is correct.

> My point is that using
> an array terminator keeps us out of this habbit of just adding parameters
> to communicate more information (as thats an ABI breaking method, and not
> particularly scalable if there is more information to be transmitted in
> the future).  Using a context sensitive API set goes beyond even that, and
> allows to retrieve arbitrary information form callbacks as needed in an
> ABI safe manner

Again I can agree with this in the general case, but it isn't necessary, in this case, to encode the information in the array since it is already local to and available in the function. It seems artificial, at this point, to implement an array terminator solution to protect an API that, effectively, hasn't been published yet.

John