Re: [PATCH] net/vhost: Add function to retreive the 'vid' for a given port id

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Tue, Sep 13, 2016 at 05:10:09PM +0200, Thomas Monjalon wrote:
> 2016-09-13 14:47, Ciara Loftus:
> > In some cases when using the vHost PMD, certain vHost library functions
> > may still need to be accessed. One such example is the
> > rte_vhost_get_queue_num function which returns the number of virtqueues
> > reported by the guest - information which is not exposed by the PMD.
> > 
> > This commit introduces a new rte_eth_vhost function that returns the
> > 'vid' associated with a given port id. This allows the PMD user to call
> > vHost library functions which require the 'vid' value.
> 
> I think we should not add any API to the PMDs.

In general, I agree with you.

> Maybe you are looking for a generic API in ethdev.

But maybe it's a bit hard to define a "right" generic API here. For this
case, the generic API I can think of could be:

- an API to get queue num, like rte_eth_get_queue_enabled_num
  I barely know NIC pmd drivers, but I doubt it's useful/meaningful for them.

- an API to get a PMD driver private (or specific) data.
  For vhost-pmd, it's vid. Again, I don't know what it could be for other nic
  drivers.

  This one may be a better option here, because it expose a key field to
  the application, vid, with which the application can invoke more vhost
  APIs. And apparently, it's not feasible to try to define a generic API
  for some (if not each) vhost APIs.
  

Or, better ideas?

	--yliu