Re: [PATCH v3 4/4] can: kvaser_usb: Add support for the Usbcan-II family

On Mon, Jan 12, 2015 at 12:51:49PM +0100, Marc Kleine-Budde wrote:

On 01/08/2015 04:19 PM, Ahmed S. Darwish wrote:

[...]

quoted

quoted

quoted

 MODULE_DEVICE_TABLE(usb, kvaser_usb_table);

@@ -463,7 +631,18 @@ static int kvaser_usb_get_software_info(struct kvaser_usb *dev)
 	if (err)
 		return err;
 
-	dev->fw_version = le32_to_cpu(msg.u.softinfo.fw_version);
+	switch (dev->family) {
+	case KVASER_LEAF:
+		dev->fw_version = le32_to_cpu(msg.u.leaf.softinfo.fw_version);
+		break;
+	case KVASER_USBCAN:
+		dev->fw_version = le32_to_cpu(msg.u.usbcan.softinfo.fw_version);
+		break;
+	default:
+		dev_err(dev->udev->dev.parent,
+			"Invalid device family (%d)\n", dev->family);
+		return -EINVAL;

The default case should not happen. I think you can remove it.

quoted

It's true, it _should_ never happen. But I only add such checks if
the follow-up code critically depends on a certain `dev->family`
behavior. So it's kind of a defensive check against any possible
bug in driver or memory.

What do you think?

The kernel is full of callback functions, if you have a bit flip there
you're in trouble anyways. A bug in the driver (or other parts of the
kernel) might overwrite the memory of dev->family, but if this happens,
more things will break.

I see. Thanks for the explanation.

Most of them are now removed in latest submission, except two to
avoid GCC warnings of variables that "may be used uninitialized".

Regards,
Darwish