Re: [PATCH v2 1/2] Added ETH_SPEED_CAP bitmap in rte_eth_dev_info

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

2015-06-18 17:06, Marc Sune:
> On 18/06/15 16:43, Morten Brørup wrote:
> > Regarding the PHY speed ABI:
> >
> > 1. The Ethernet PHY ABI for speed, duplex, etc. should be common throughout the entire DPDK. It might be confusing if some structures/functions use a bitmask to indicate PHY speed/duplex/personality/etc. and other structures/functions use a combination of an unsigned integer, duplex flag, personality enumeration etc. (By personality enumeration, I am referring to PHYs with multiple electrical interfaces. E.g. a dual personality PHY might have both an RJ45 copper interface and an SFP module interface, whereof only one can be active at any time.)
> 
> Thomas was sending a similar comment and I agreed to do a unified speed 
> bitmap for both capabilities and link negotiation/link info (v3, waiting 
> for 2.2 merge window):
> 
> http://dpdk.org/ml/archives/dev/2015-June/019207.html

It would be better to try merging it in 2.1 while keeping an ABI backward
compatibility.

> > 2. The auto-negotiation standard allows the PHY to announce (to its link
> > partner) any subset of its capabilities to its link partner. E.g. a
> > standard 10/100/100 Ethernet PHY (which can handle both 10 and 100 Mbit/s
> > in both half and full duplex and 1 Gbit/s full duplex) can be configured
> > to announce 10 Mbit/s half duplex and 100 Mbit/s full duplex capabilities
> > to its link partner. (Of course, more useful combinations are normally
> > announced, but the purpose of the example is to show that any combination
> > is possible.)
> >
> > The ABI for auto-negotiation should include options to select the list of
> > capabilities to announce to the link partner. The Linux PHY ABI only
> > allows forcing a selected speed and duplex (thereby disabling
> > auto-negotiation) or enabling auto-negotiation (thereby announcing all
> > possible speeds and duplex combinations the PHY is capable of). Don't make
> > the same mistake in DPDK.
> 
> I see what you mean, and you are probably right. In any case this is for 
> a separate patch, if we think it is a necessary feature to implement.
> 
> Nevertheless, this makes me rethink about the proposal from Thomas about 
> unifying _100_HD/_100_FD to 100M, because you will need this 
> granularity, eventually. @Thomas: opinions?

I think Morten's advice is good.
Are we going to have half duplex links for PHY faster than 100M?
If not, we can manage them with a hackish define 100M_HD and a 100M
which implicitly means full duplex.