[dpdk-dev] [PATCH v5 3/8] ethdev: reserve capability flags for PMD-specific API

[Tiwei Bie]

On Thu, Jan 05, 2017 at 01:44:18AM +0800, Ananyev, Konstantin wrote:
[...]
> > >
> > > I understand that.
> > > My question was: suppose user would like to create a bonded device over 2 NICs.
> > > One of them is ixgbe, while other would be some other type.
> > > In future get_dev_info() for each of them might return DEV_RX_OFFLOAD_RESERVED_0  bit as set.
> > > But it would mean completely different thing.
> > > How bonded device would know that to deal properly?
> > >
> > > Another example - user has 2 NICs of different type and would like to send the same packet on both of them simultaneously.
> > > As PKT_TX_RESERVED might mean different things for these devices, and user would like to use let say
> > > PKT_TX_IXGBE_MACSEC on one of them, he would need to do a copy of them, instead just increment a refcnt.
> > >
> > > Similar issues might arise at RX handling: user got a packet with PKT_RX_RESERVED_0 set.
> > > What does it really mean if there are different NIC types in the system?
> > > The only way to answer that question, as I can see,  is to keep track from what NIC that packet was received.
> > > Which I suppose, is not always convenient.
> > >
> > 
> > The main purpose is to put the PMD-specific APIs in a separate
> > namespace instead of mixing the PMD-specific APIs and global APIs
> > up, and also save the bits in mbuf.ol_flags.
> > 
> > There are other ways to achieve this goal, such as introducing
> > the PMD specific ol_flags in mbuf second cache line as you said.
> > I just thought defining some reserved bits seems to be the most
> > simple way which won't introduce many changes.
> > 
> > What's your suggestions? Should I just revert the changes and
> > define the generic flags directly?
> 
> Yes, that would be my preference.
> As I said above - spending extra bit in ol_flags  doesn't look like a big problem to me.
> In return there would be no need to consider how to handle all that confusing scenarios in future.

Okay. I'll update my patches. Thanks a lot for your comments.

Thanks & regards,
Tiwei Bie