[dpdk-dev] [PATCH v2 1/2] Added ETH_SPEED_CAP bitmap in rte_eth_dev_info

["Morten Brørup" <mb@smartsharesystems.com>]

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.)

 

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.

 

PS: While working for Vitesse Semiconductors (an Ethernet chip company) a long time ago, I actually wrote the API for their line of Ethernet PHYs. So I have hands on experience in this area.

 

 

Med venlig hilsen / kind regards

 

Morten Brørup

CTO

 

 

 

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