Re: [PATCH net-next v5 13/13] ax88796b: Add support for AX88772D, AX88179A and AX88279

> I also would like to add another feature to phylink separately. All the USB
> Ethernet controllers have a feature where the controller sends a USB Interrupt
> URB to the host when the link state changes. It would be great if instead
> of polling, this could be used to trigger a read_status() of the PHY instead
> of polling it constantly over USB. This would work like the equivalent of the
> PHY link state change interrupts. Basically, the host driver would, upon
> receiving a link change interrupt URB trigger a similar code path in phylink
> as a link change interrupt by a PHY triggers. Ideally, this could be something
> that usbnet would help drivers to set up. Would that make sense?

There are already a few different implementations of this.

phylib has phy_mac_interrupt(). You might just want to put a phylink
wrapper around this. You would still have the polling, but calling
this would trigger an immediate poll, speeding things up a bit. You
might be able to disable the polling with PHY_MAC_INTERRUPT.

These is also phylink_mac_change(). But as the name suggests, that is
about the MAC seeing a change in state, not that it knows the PHY
changed state. I don't think it triggers phylib.

Another option is to implement a Linux interrupt
controller. mv88e6xxx_g1_irq_setup_common() is one example which i
wrote. The Marvell Ethernet Switch chips have embedded interrupt
controllers, including PHY interrupts.  The switch chip has one output
pin often connected to a GPIO which can trigger an interrupt. When
that GPIO interrupt fires, it calls mv88e6xxx_g1_irq_thread_fn() to
dispatch the interrupt. That then uses handle_nested_irq() to pass on
the interrupt to anything which has called request_irq() with the
appropriate values. Now phylib has that, phy_request_interrupt(). For
that to work, you need phydev->irq set. That comes from
mii_bus->irq[]. So when creating your MDIO bus, you first create the
interrupt controller, and then set bus->irq[],
mv88e6xxx_g2_irq_mdio_setup(). phylib should then glue it all
together.

	Andrew