Re: [PATCH v3 2/2] net: phy: add marvell usb to mdio controller

["Tobias Waldekranz" <tobias@waldekranz.com>]

On Sun Mar 22, 2020 at 8:40 AM, Greg KH wrote:
> From a USB point of view, it looks sane, only one question:

Great, thanks for the review.

> > +static int mvusb_mdio_probe(struct usb_interface *interface,
> > +			    const struct usb_device_id *id)
> > +{
> > +	struct device *dev = &interface->dev;
> > +	struct mvusb_mdio *mvusb;
> > +	struct mii_bus *mdio;
> > +
> > +	mdio = devm_mdiobus_alloc_size(dev, sizeof(*mvusb));
>
> 
> You allocate a bigger buffer here than the original pointer thinks it is
> pointing to?

Yes. I've seen this pattern in a couple of places in the kernel,
e.g. alloc_netdev also does this. The object is extended with the
requested size, and the offset is stored somewhere for later use by
the driver.

> > +	if (!mdio)
> > +		return -ENOMEM;
> > +
> > +	mvusb = mdio->priv;
>
> 
> And then you set this pointer here?

...in this case in the priv member.

https://code.woboq.org/linux/linux/drivers/net/phy/mdio_bus.c.html#143

Thanks