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

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Date:	Fri, 20 Jul 2012 13:58:20 -0700
From:	John Fastabend <john.r.fastabend@...el.com>
To:	Ben Hutchings <bhutchings@...arflare.com>
CC:	Jiri Pirko <jiri@...nulli.us>, or.gerlitz@...il.com,
	davem@...emloft.net, roland@...nel.org, netdev@...r.kernel.org,
	ali@...lanox.com, sean.hefty@...el.com, shlomop@...lanox.com,
	"Ronciak, John" <john.ronciak@...el.com>
Subject: Re: [RFC PATCH] net: Add support for virtual machine device queues
 (VMDQ)

On 7/20/2012 11:01 AM, Ben Hutchings wrote:
> On Fri, 2012-07-20 at 09:30 -0700, John Fastabend wrote:
>> On 7/18/2012 11:42 PM, Jiri Pirko wrote:
>>> Thu, Jul 19, 2012 at 12:05:44AM CEST, john.r.fastabend@...el.com 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.
>
> The code assumes that it is the size of a single pointer...
>
> Ben.
>

Right I'll fix it. Worked for me because my local unfinished
driver implementation only stored a single pointer. Thanks Ben.

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