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

On Sun, Dec 28, 2014 at 10:51:34PM +0100, Olivier Sobrie wrote:
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+	if (LEAF_PRODUCT_ID(id->idProduct)) {
+		dev->family = KVASER_LEAF;
+		dev->max_channels = LEAF_MAX_NET_DEVICES;
+	} else if (USBCAN_PRODUCT_ID(id->idProduct)) {
+		dev->family = KVASER_USBCAN;
+		dev->max_channels = USBCAN_MAX_NET_DEVICES;
+	} else {
+		dev_err(&intf->dev, "Product ID (%d) does not belong to any "
+				    "known Kvaser USB family", id->idProduct);
+		return -ENODEV;
+	}
+

Is it really required to keep max_channels in the kvaser_usb structure?
If I looked correctly, you use this variable as a replacement for
MAX_NET_DEVICES in the code and MAX_NET_DEVICES is only used in probe
and disconnect functions. I think it can even be replaced by nchannels
in the disconnect path. So I also think that it don't need to be in the
kvaser_usb structure.

hmmm.. given the current state of error arbitration explained
above, where I cannot accept a dev->nchannels > 2, I guess we
have two options:

a) Remove max_channels, and hardcode the channels count
correctness logic as follows:

        dev->nchannels = msg.u.cardinfo.nchannels;
        if ((dev->family == USBCAN && dev->nchannels > USBCAN_MAX_NET_DEVICES)
            || (dev->family == LEAF && dev->nchannels > LEAF_MAX_NET_DEVICES))
                return -EINVAL

b) Leave max_channels in 'struct kvaser_usb' as is.

I personally prefer the solution at 'b)' but I can do it as
in 'a)' if you prefer :-)

Keeping max_channels in the kvaser_usb structure is useless because it
is only used in one function that is called in the probe function.

I would prefer to have:
	if (dev->nchannels > MAX_NET_DEVICES)
		return -EINVAL

	if ((dev->family == USBCAN) &&
	    (dev->nchannels > MAX_USBCAN_NET_DEVICES))
		return -EINVAL

You can remove LEAF_MAX_NET_DEVICES which is not used, keep
MAX_NET_DEVICES equals to 3 and remove the MAX() macro.
The test specific to the USBCAN family can eventually be moved in the
kvaser_usb_probe() function.

Quite nice, will do it that way in v3.

Regards,
Darwish