[PATCH 0/4] ethtool: implement Energy Detect Powerdown support via phy-tunable

[Alexandru Ardelean]

This patch series is actually 2 series in 1.

First 2 patches implement the kernel support for controlling Energy Detect
Powerdown support via phy-tunable, and the next 2 patches implement the
ethtool user-space control.
Hopefully, this combination of 2 series is an acceptable approach; if not,
I am fine to re-update it based on feedback.

The `phy_tunable_id` has been named `ETHTOOL_PHY_EDPD` since it looks like
this feature is common across other PHYs (like EEE), and defining
`ETHTOOL_PHY_ENERGY_DETECT_POWER_DOWN` seems too long.
    
The way EDPD works, is that the RX block is put to a lower power mode,
except for link-pulse detection circuits. The TX block is also put to low
power mode, but the PHY wakes-up periodically to send link pulses, to avoid
lock-ups in case the other side is also in EDPD mode.
    
Currently, there are 2 PHY drivers that look like they could use this new
PHY tunable feature: the `adin` && `micrel` PHYs.

This series updates only the `adin` PHY driver to support this new feature,
as this chip has been tested. A change for `micrel` can be proposed after a
discussion of the PHY-tunable API is resolved.

-- 
2.20.1