Re: [dpdk-dev] [PATCH v3] ethdev: fix DCB config issue on ixgbe

["Lu, Wenzhuo" <wenzhuo.lu@intel.com>]

Hi Thomas,


> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
> Sent: Thursday, June 23, 2016 8:22 PM
> To: Lu, Wenzhuo
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH v3] ethdev: fix DCB config issue on ixgbe
> 
> 2016-06-23 01:04, Lu, Wenzhuo:
> > From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
> > > 2016-05-06 05:33, Wenzhuo Lu:
> > > > +int
> > > > +rte_eth_dev_mq_mode_set(uint8_t port_id,
> > > > +			enum rte_eth_rx_mq_mode rx_mq_mode,
> > > > +			enum rte_eth_tx_mq_mode tx_mq_mode);
> > >
> > > I've really tried to think about it and I think it is more or less a hack.
> > > First, it is not explained in the doc when we should use
> > > rte_eth_dev_mq_mode_set() instead of a simple call to
> rte_eth_dev_configure().
> > > Second, I don't understand why having a function which configures
> > > the "multiqueue modes" without configuring properly RSS/VMDq/DCB.
> > > Last, it is said that rte_eth_dev_configure() "must be invoked first
> > > before any other function in the Ethernet API".
> > Sorry, didn't notice this announcement.
> >
> > > My opinion is that the primary goal of rte_eth_dev_configure() was
> > > "Embedding all configuration information in a single data structure"
> > > but it is currently configuring only speed and some flow steering
> > > (only RSS, VMDq, DCB and flow director).
> > > This bug and the state of the ethdev API clearly shows that we must
> > > have one function per feature (or group of features) and drop
> rte_eth_dev_configure().
> > >
> > > You can argue it is a just a personal feeling and this comment comes
> > > late, but I promise it is not easy to give a negative opinion because of design
> perspective.
> > > I strongly feel we must stop workarounding the ethdev API issues and
> > > start really fixing it.
> > >
> > > Hope you understand and agree to work on a new API.
> > I have the same feeling with you. There's some problem with
> rte_eth_dev_configure. So this patch is a workaround more than a real fix.
> > But the problem is this API has already been used. What I think is could we take
> this workaround as a first step. It need not ask the APP to change too much.
> > Then we can discuss how could we rework on a new API or APIs. We all
> > know the change in rte layer is not easy and need to be very careful
> > :)
> 
> We probably need more opinions.
> I think it is not a good idea to introduce a new API only to workaround another
> one and keep confusion in place.
> A similar approach which looks better is to introduce a new API which will partly
> replace the old one and will remain a good one when the old API will be
> completely removed.
> In other words, we should introduce a good API for flow steering as soon as
> possible and deprecate rte_eth_dev_configure().
I think you're right. The workaround can make things confusing. Better to introduce a new API to replace rte_eth_dev_configure.