Subject: Re: [RFC PATCH] net: Add support for virtual machine device queues (VMDQ)

From: John Fastabend <[email-masked]>
Date: Fri, 20 Jul 2012 09:30:47 -0700

On 7/18/2012 11:42 PM, Jiri Pirko wrote:
> Thu, Jul 19, 2012 at 12:05:44AM CEST, [email-masked] wrote:
>> This adds support to allow virtual net devices to be created. These
>> devices can be managed independtly of the physical function but
>> use the same physical link.

[...]

>> +
>> +size_t vmdq_getpriv_size(struct net *src_net, struct nlattr *tb[])
>> +{
>> +	struct net_device *lowerdev;
>> +
>> +	if (!tb[IFLA_LINK])
>> +		return -EINVAL;
>> +
>> +	lowerdev = __dev_get_by_index(src_net, nla_get_u32(tb[IFLA_LINK]));
>> +	if (!lowerdev)
>> +		return -ENODEV;
>> +
>> +	return sizeof(netdev_priv(lowerdev));
>> +}
>
> Why exactly do you need to have the priv of same size as lowerdev? I do
> not see you use that anywhere...
>

When we add a child device the hardware/sw may have some private data
it needs to manage this device.

I made an assumption here that the priv space for child devices is the
same as the lowerdev but this might be a bad assumption.

.John