netdev - RE: [patch net-next RFC 07/12] dsa: implement ndo_swdev_get

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Date:	Fri, 22 Aug 2014 09:05:54 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Florian Fainelli' <f.fainelli@...il.com>,
	Jiri Pirko <jiri@...nulli.us>
CC:	netdev <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	"Neil Horman" <nhorman@...driver.com>,
	Andy Gospodarek <andy@...yhouse.net>, tgraf <tgraf@...g.ch>,
	dborkman <dborkman@...hat.com>, ogerlitz <ogerlitz@...lanox.com>,
	jesse <jesse@...ira.com>, pshelar <pshelar@...ira.com>,
	azhou <azhou@...ira.com>, Ben Hutchings <ben@...adent.org.uk>,
	Stephen Hemminger <stephen@...workplumber.org>,
	"Jeff Kirsher" <jeffrey.t.kirsher@...el.com>,
	vyasevic <vyasevic@...hat.com>,
	"Cong Wang" <xiyou.wangcong@...il.com>,
	John Fastabend <john.r.fastabend@...el.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	Scott Feldman <sfeldma@...ulusnetworks.com>,
	Roopa Prabhu <roopa@...ulusnetworks.com>,
	John Linville <linville@...driver.com>,
	dev <dev@...nvswitch.org>,
	"jasowang@...hat.com" <jasowang@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Nicolas Dichtel <nicolas.dichtel@...nd.com>,
	Sergey Ryazanov <ryazanov.s.a@...il.com>,
	Lennert Buytenhek <buytenh@...tstofly.org>,
	Aviad Raveh <aviadr@...lanox.com>,
	Felix Fietkau <nbd@...nwrt.org>,
	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Neil Jerram <Neil.Jerram@...aswitch.com>,
	"ronye@...lanox.com" <ronye@...lanox.com>
Subject: RE: [patch net-next RFC 07/12] dsa: implement ndo_swdev_get_id

From: Florian Fainelli
> 2014-08-21 10:06 GMT-07:00 Jiri Pirko <jiri@...nulli.us>:
> > Thu, Aug 21, 2014 at 06:56:13PM CEST, f.fainelli@...il.com wrote:
> >>2014-08-21 9:19 GMT-07:00 Jiri Pirko <jiri@...nulli.us>:
> >>> Signed-off-by: Jiri Pirko <jiri@...nulli.us>
> >>> ---
> >>>  net/dsa/Kconfig |  2 +-
> >>>  net/dsa/slave.c | 16 ++++++++++++++++
> >>>  2 files changed, 17 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig
> >>> index f5eede1..66c445a 100644
> >>> --- a/net/dsa/Kconfig
> >>> +++ b/net/dsa/Kconfig
> >>> @@ -1,6 +1,6 @@
> >>>  config HAVE_NET_DSA
> >>>         def_bool y
> >>> -       depends on NETDEVICES && !S390
> >>> +       depends on NETDEVICES && NET_SWITCHDEV && !S390
> >>>
> >>>  # Drivers must select NET_DSA and the appropriate tagging format
> >>>
> >>> diff --git a/net/dsa/slave.c b/net/dsa/slave.c
> >>> index 45a1e34..e069ba3 100644
> >>> --- a/net/dsa/slave.c
> >>> +++ b/net/dsa/slave.c
> >>> @@ -171,6 +171,19 @@ static int dsa_slave_ioctl(struct net_device *dev, struct ifreq *ifr, int
> cmd)
> >>>         return -EOPNOTSUPP;
> >>>  }
> >>>
> >>> +static int dsa_slave_swdev_get_id(struct net_device *dev,
> >>> +                                 struct netdev_phys_item_id *psid)
> >>> +{
> >>> +       struct dsa_slave_priv *p = netdev_priv(dev);
> >>> +       struct dsa_switch *ds = p->parent;
> >>> +       u64 tmp = (u64) ds;
> >>> +
> >>> +       /* TODO: add more sophisticated id generation */
> >>> +       memcpy(&psid->id, &tmp, sizeof(tmp));
> >>> +       psid->id_len = sizeof(tmp);
> >>
> >>There is already an unique id generated, which is the index in the
> >>switch tree, and which is stored in struct dsa_switch, so this could
> >>probably be simplified to:
> >>
> >>psid->id = ds->index
> >
> > That index is 0..n if I understand that correctly. That is not enough.
> > The point is to have unique id for every chip in the system. If we would
> > have 0,1,2... the collision is very likely.
> 
> Good point, so an unique index for DSA switches could look like the
> DSA platform device id plus the switch index in the tree..., but then
> we would need something like (pdev->id << N) | switch index, so that
> would not give a consistent naming scheme across different devices.

Do you also need to worry about the 'lifetime' of these ids?
In which case some of the high bits need to be used as 'generation number'.

	David

> Maybe we are just better with using the Linux IDR API in include/linux/idr.h?
> --
> Florian