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

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.

quoted

+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.

quoted

+	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