Re: [dpdk-dev] [PATCH v2 07/11 1/2] vdev: new registration API

[Thomas Monjalon <thomas.monjalon@6wind.com>]

Hi Bruce,

11/04/2014 20:08, Richardson, Bruce :
> From: Neil Horman
> > On Fri, Apr 11, 2014 at 06:18:08PM +0200, Thomas Monjalon wrote:
> > > It seems that your patch is not removing
> > > rte_eth_ring_pair_create/rte_eth_ring_pair_attach so I'm not sure you
> > > can dynamically change the PMD in this case.
> > 
> > Ew, I had missed those calls.  Yes, those should be encapsulated as some
> > driver ops or some such.  I'll look at that when I rebase.  Regardless
> > however, I didn't mean to state that pmds could be switched while
> > running, only that the pmd to use could be specified at run time. 
> > Though, you're correct, pmd_ring doesn't seem to hold in line with the
> > other pmds in their isolation.
> 
> The ring PMD is probably best treated separately from the other PMDs as it's
> not really a device poll-mode driver. Instead, it's a general library that
> presents an API to make a ring, or set of rings, appear as a poll-mode
> driver ethdev. The EAL command to have one created at startup time was just
> an addon after-the-fact in case someone might find it useful :-). However,
> it's primary purpose was to allow applications to be written which could
> use physical NICs or rings interchangeably. For example, an app with
> multiple stages in a pipeline, where each stage just reads from an ethdev
> without caring if it's actually reading from a port or from packets sent
> from another lcore/function etc. Another example might be where an
> application wishes to sometimes loop packets back to itself, in this case
> it uses the C API to create an additional ring ethdev which it uses as
> output port for any packets it wants looped back - no special handling
> needed, everything is an ethdev to it on which it calls rx_burst or
> tx_burst. It's also likely that in future we will develop other libraries
> which wish to present their functionality via rx_burst/tx_burst functions
> i.e. as an ethdev.

I think you are describing a vdev and you want to be able to instantiate this 
vdev in your application code. Right?
So why not make a generic API to be able to instantiate a vdev?

-- 
Thomas