From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ben Hutchings <bhutchings@solarflare.com>
Subject: Re: [RFC PATCH] net: Add support for virtual machine device queues
 (VMDQ)
Date: Fri, 20 Jul 2012 19:01:20 +0100
Message-ID: <1342807280.2678.33.camel@bwh-desktop.uk.solarflarecom.com>
References: <20120718220544.22619.97136.stgit@i40e.jf1>
	 <20120719064258.GA1665@minipsycho.orion> <500987B7.2030705@intel.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
Cc: Jiri Pirko <jiri@resnulli.us>, <or.gerlitz@gmail.com>,
	<davem@davemloft.net>, <roland@kernel.org>,
	<netdev@vger.kernel.org>, <ali@mellanox.com>,
	<sean.hefty@intel.com>, <shlomop@mellanox.com>,
	"Ronciak, John" <john.ronciak@intel.com>
To: John Fastabend <john.r.fastabend@intel.com>
Return-path: <netdev-owner@vger.kernel.org>
Received: from webmail.solarflare.com ([12.187.104.25]:55186 "EHLO
	ocex02.SolarFlarecom.com" rhost-flags-OK-OK-OK-FAIL)
	by vger.kernel.org with ESMTP id S1751874Ab2GTSBZ (ORCPT
	<rfc822;netdev@vger.kernel.org>); Fri, 20 Jul 2012 14:01:25 -0400
In-Reply-To: <500987B7.2030705@intel.com>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

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@intel.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.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.