Re: [RESEND,net-next] mdio: Make use of bus callbacks

[Jakub Kicinski <kuba@kernel.org>]

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---
mdio: Make use of bus callbacks

This patch moves MDIO device probe/remove/shutdown callbacks from the
device_driver level to the bus_type level, with the goal of eventually
removing device_driver callbacks.

> diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
> index afdf1ad6c0e6..dea67470a7bf 100644
> --- a/drivers/net/phy/mdio_bus.c
> +++ b/drivers/net/phy/mdio_bus.c

[ ... ]

> @@ -1004,11 +1004,67 @@ static const struct attribute_group *mdio_bus_dev_groups[] = {
>  	NULL,
>  };
>
> +/**
> + * mdio_bus_probe - probe an MDIO device
> + * @dev: device to probe
> + *
> + * Description: Take care of setting up the mdio_device structure
> + * and calling the driver to probe the device.
> + *
> + * Return: Zero if successful, negative error code on failure
> + */
> +static int mdio_bus_probe(struct device *dev)
> +{
> +	struct mdio_device *mdiodev = to_mdio_device(dev);
> +	struct device_driver *drv = dev->driver;
> +	struct mdio_driver *mdiodrv = to_mdio_driver(drv);

[ ... ]

>  const struct bus_type mdio_bus_type = {
>  	.name		= "mdio_bus",
>  	.dev_groups	= mdio_bus_dev_groups,
>  	.match		= mdio_bus_match,
>  	.uevent		= mdio_uevent,
> +	.probe		= mdio_bus_probe,
> +	.remove		= mdio_bus_remove,
> +	.shutdown	= mdio_bus_shutdown,
>  };

Does adding these bus-level callbacks break PHY device probing?

PHY drivers register via phy_driver_register() which sets:

    new_driver->mdiodrv.driver.probe = phy_probe;
    new_driver->mdiodrv.driver.remove = phy_remove;

The driver core in call_driver_probe() prioritizes bus callbacks over driver
callbacks:

    if (dev->bus->probe)
        ret = dev->bus->probe(dev);
    else if (drv->probe)
        ret = drv->probe(dev);

With mdio_bus_type.probe now set, phy_probe() will never be called for PHY
devices. The same applies to phy_remove() being bypassed by mdio_bus_remove().

phy_probe() performs essential initialization including setting phydev->drv,
reading PHY abilities, configuring EEE, and setting up the state machine.
Without this, PHY devices would fail to initialize properly.

Was there a plan to update phy_driver_register() as part of this change, or
is a separate patch needed to handle PHY drivers?
-- 
pw-bot: cr