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From: Kurt Van Dijck <kurt.van.dijck@eia.be>
To: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Fabio Baltieri <fabio.baltieri@gmail.com>,
	linux-can@vger.kernel.org, linux-kernel@vger.kernel.org,
	Oliver Hartkopp <socketcan@hartkopp.net>,
	Wolfgang Grandegger <wg@grandegger.com>
Subject: Re: [PATCH can-next v6] can: add tx/rx LED trigger support
Date: Mon, 3 Sep 2012 20:13:35 +0200	[thread overview]
Message-ID: <20120903181335.GA415@vandijck-laurijssen.be> (raw)
In-Reply-To: <5044A547.2010603@pengutronix.de>

On Mon, Sep 03, 2012 at 02:40:39PM +0200, Marc Kleine-Budde wrote:
> On 08/25/2012 12:01 AM, Fabio Baltieri wrote:
> > Hello Kurt,
> > 
> > On Fri, Aug 24, 2012 at 02:42:48PM +0200, Kurt Van Dijck wrote:
> >> On Fri, Aug 24, 2012 at 01:28:16PM +0200, Marc Kleine-Budde wrote:
> >>> On 08/24/2012 07:10 AM, Kurt Van Dijck wrote:
> >>>> Hello,
> >>>>
> >>>> I find the CAN led triggers an interesting thing.
> >>>>
> >>>> And then, this scenario fell crossed my mind:
> >>>> Imagine I do:
> >>>> [insert CAN device: can0]
> >>>> $ ip link set can0 name helga
> >>>> [insert another CAN device: again 'can0']
> >>>>
> >>>> Registering 'can0-tx' led trigger will fail for the second CAN device,
> >>>> since that led trigger name is already reserved for CAN device 'helga'.
> >>> Good point.
> > 
> > Yep, thanks for pointing that out!
> > 
> > Interface renaming was something I considered when I first wrote the
> > code and I had the mac80211-led driver in mind, as that driver uses the
> > phy name and not the netdev one for its triggers.
> > 
> > The reason why I did not care that much in the end is that on SoC based
> > systems trigger-led association is made at probe time, based on data
> > either from platform_data or devicetree, so I imagined that once the
> > kernel is ported to the board and default triggers are set correctly at
> > boot time, the userspace is free to rename CAN interfaces and nobody
> > should notice... :^)
> > 
> > The thing I did not consider are hot-plug interfaces mixed with
> > renaming, such as in the case you pointed out - it's probably not really
> > common but still possible.
> > 
> >>>> I'm not sure how to fix such.
> >>>> If 'rx' & 'tx' may be combined, reusing the netdev name may be possible?
> >>>> Just wild thinking ...
> >>>
> >>> I think the device's name (not netdev) is unique in the system and
> >>> cannot be changed.
> >>
> >> but may contain several netdev's ...
> > 
> > Ouch.
> 
> The net->ifindex is unique. But it's only an integer. Usually can0 has a
> ifindex != 0, so a simple can%d is contra productive here.
> 
> Some pointers to related code:
> http://lxr.free-electrons.com/source/drivers/base/core.c#L1847
> http://lxr.free-electrons.com/source/drivers/base/core.c#L73
> http://lxr.free-electrons.com/source/include/linux/device.h#L695
> 
> comments?

a very recent idea: something with netdevice notifiers and NETDEV_CHANGENAME ...
http://lxr.free-electrons.com/source/net/core/dev.c#L1030

you could: rename the trigger, or if we think it's usefull,
block the netdev rename when its triggers are in use.

Kurt

  reply	other threads:[~2012-09-03 18:13 UTC|newest]

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-07-30 19:20 [PATCH can-next v3 1/2] can: add tx/rx LED trigger support Fabio Baltieri
2012-07-30 19:20 ` [PATCH can-next v3 2/2] can: flexcan: add " Fabio Baltieri
2012-07-30 21:17 ` [PATCH can-next v3 1/2] can: add tx/rx " Marc Kleine-Budde
2012-07-31  6:57   ` Fabio Baltieri
2012-07-31  7:10     ` Marc Kleine-Budde
2012-07-31 11:57       ` Fabio Baltieri
2012-07-31 12:00         ` Marc Kleine-Budde
2012-07-31 22:05           ` [PATCH can-next v4] " Fabio Baltieri
2012-08-01  9:36             ` Marc Kleine-Budde
2012-08-01 10:07               ` Marc Kleine-Budde
2012-08-01 10:30               ` Fabio Baltieri
2012-08-01 11:37                 ` Marc Kleine-Budde
2012-08-01 11:49               ` [PATCH can-next v5 1/2] " Fabio Baltieri
2012-08-01 11:49                 ` [PATCH can-next v5 2/2] can: flexcan: add " Fabio Baltieri
2012-08-01 11:53                   ` Marc Kleine-Budde
2012-08-01 12:24                     ` Fabio Baltieri
2012-08-01 12:30                       ` Marc Kleine-Budde
2012-08-01 21:02                   ` Marc Kleine-Budde
2012-08-01 11:59                 ` [PATCH can-next v5 1/2] can: add tx/rx " Marc Kleine-Budde
2012-08-01 12:06                 ` Oliver Hartkopp
2012-08-01 12:18                   ` Marc Kleine-Budde
2012-08-01 18:21                     ` [PATCH can-next v6] " Fabio Baltieri
2012-08-01 21:00                       ` Marc Kleine-Budde
2012-08-01 22:38                         ` Fabio Baltieri
2012-08-01 21:05                       ` Oliver Hartkopp
2012-08-24  5:10                       ` Kurt Van Dijck
2012-08-24 11:28                         ` Marc Kleine-Budde
2012-08-24 12:42                           ` Kurt Van Dijck
2012-08-24 22:01                             ` Fabio Baltieri
2012-08-25 20:25                               ` Kurt Van Dijck
2012-09-03 12:40                               ` Marc Kleine-Budde
2012-09-03 18:13                                 ` Kurt Van Dijck [this message]
2012-09-03 18:29                                   ` Fabio Baltieri
2012-09-03 20:54                                     ` Oliver Hartkopp
2012-09-04  7:11                                       ` Kurt Van Dijck
2012-09-04  9:29                                         ` [PATCH] can: rename LED trigger name on netdev renames Kurt Van Dijck
2012-09-06 18:59                                           ` Fabio Baltieri
2012-09-06 19:31                                             ` Oliver Hartkopp
2012-09-06 20:46                                               ` Fabio Baltieri
2012-09-07  7:19                                                 ` Kurt Van Dijck
2012-09-09 16:17                                                   ` [PATCH v2] " Fabio Baltieri
2012-09-10 14:25                                                     ` [PATCH] can: export a safe netdev_priv wrapper for candev Kurt Van Dijck
2012-09-10 18:22                                                       ` Oliver Hartkopp
2012-09-10 18:29                                                       ` Fabio Baltieri
2012-09-10 19:55                                                         ` [PATCH v2] " Kurt Van Dijck
2012-09-10 14:28                                                     ` [PATCH v3] can: rename LED trigger name on netdev renames Kurt Van Dijck
2012-09-10 18:25                                                       ` Oliver Hartkopp
2012-09-10 18:40                                                         ` Fabio Baltieri
2012-09-10 19:01                                                           ` Oliver Hartkopp
2012-09-10 20:08                                                             ` Kurt Van Dijck
2012-09-11  5:42                                                               ` Oliver Hartkopp
2012-09-11  7:13                                                                 ` Fabio Baltieri
2012-09-12  7:22                                                                   ` Kurt Van Dijck
2012-09-11  8:05                                                               ` Kurt Van Dijck
2012-09-10 20:06                                                           ` [PATCH v4] " Kurt Van Dijck
2012-09-11 21:04                                                             ` Fabio Baltieri
2012-09-04 20:15                                         ` [PATCH can-next v6] can: add tx/rx LED trigger support Fabio Baltieri
2012-09-06 10:33                                           ` Kurt Van Dijck
2012-09-06 11:17                                             ` Fabio Baltieri
2012-09-06 15:11                                               ` Kurt Van Dijck
2012-09-06 20:57                                                 ` Fabio Baltieri
2012-09-07  7:04                                                   ` Kurt Van Dijck
2012-09-07 18:59                                                     ` Fabio Baltieri
2012-07-31  8:46 ` [PATCH can-next v3 1/2] " Wolfgang Grandegger
2012-07-31 10:12   ` Marc Kleine-Budde
2012-07-31 11:55     ` Fabio Baltieri
2012-07-31 12:14   ` Fabio Baltieri

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