From: Fabio Baltieri <fabio.baltieri@gmail.com>
To: Kurt Van Dijck <kurt.van.dijck@eia.be>
Cc: Marc Kleine-Budde <mkl@pengutronix.de>,
Oliver Hartkopp <socketcan@hartkopp.net>,
Wolfgang Grandegger <wg@grandegger.com>,
linux-kernel@vger.kernel.org, linux-can@vger.kernel.org
Subject: Re: [PATCH] can: rename LED trigger name on netdev renames
Date: Thu, 6 Sep 2012 20:59:38 +0200 [thread overview]
Message-ID: <20120906185938.GA4043@gmail.com> (raw)
In-Reply-To: <1346750951-10451-1-git-send-email-kurt.van.dijck@eia.be>
Hi Kurt,
thanks for the patch!
On Tue, Sep 04, 2012 at 11:29:11AM +0200, Kurt Van Dijck wrote:
> The LED trigger name for CAN devices is based on the initial
> CAN device name, but does never change. The LED trigger name
> is not guaranteed to be unique in case of hotplugging CAN devices.
>
> This patch tries to address this problem by modifying the
> LED trigger name according to the CAN device name when
> the latter changes.
That's an ideal solution, and I like the notifier implementation, but I
see a couple of problems with it.
> This patch is meant as illustration only.
> In case of VCAN device rename, a segmentation fault will occur.
>
> Signed-off-by: Kurt Van Dijck <kurt.van.dijck@eia.be>
> ---
> drivers/net/can/led.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 57 insertions(+)
>
> diff --git a/drivers/net/can/led.c b/drivers/net/can/led.c
> index eaa14ac..f62f908 100644
> --- a/drivers/net/can/led.c
> +++ b/drivers/net/can/led.c
> @@ -12,6 +12,7 @@
> #include <linux/slab.h>
> #include <linux/netdevice.h>
> #include <linux/can/dev.h>
> +#include <linux/if_arp.h>
>
> #include <linux/can/led.h>
>
> @@ -87,3 +88,59 @@ void devm_can_led_init(struct net_device *netdev)
> devres_add(&netdev->dev, res);
> }
> EXPORT_SYMBOL_GPL(devm_can_led_init);
> +
> +/*
> + * NETDEV rename notifier to rename the associated led triggers too
> + */
> +static int can_led_notifier(struct notifier_block *nb, unsigned long msg,
> + void *data)
> +{
> + struct net_device *netdev = (struct net_device *)data;
> + struct can_priv *priv = netdev_priv(netdev);
> + int busy = 0;
> +
> + if (!net_eq(dev_net(netdev), &init_net))
> + return NOTIFY_DONE;
> +
> + if (netdev->type != ARPHRD_CAN)
> + return NOTIFY_DONE;
> +
> + if (msg != NETDEV_CHANGENAME)
> + return NOTIFY_DONE;
That's the main problem, which I also got stuck into when I did my first
can-led implementation. As LED structures are in netdev's private data,
you can only use it if your driver is based on the can-dev API, and
there are no way to be sure of that if you get outside driver's code
itself.
This would give problems with vcan, slcan, and probabily other
non-mainlined drivers.
Is there any way to register a notifier which fires only for devices
registered with devm_can_led_init?
> + read_lock(&priv->tx_led_trig->leddev_list_lock);
> + if (!list_empty(&priv->tx_led_trig->led_cdevs))
> + ++busy;
> + read_unlock(&priv->tx_led_trig->leddev_list_lock);
> + read_lock(&priv->rx_led_trig->leddev_list_lock);
> + if (!list_empty(&priv->rx_led_trig->led_cdevs))
> + ++busy;
> + read_unlock(&priv->rx_led_trig->leddev_list_lock);
> +
> + if (busy)
> + return notifier_from_errno(-EBUSY);
As we were discussing in the other thread, I don't think that this is
necessary.
> + snprintf(priv->tx_led_trig_name, sizeof(priv->tx_led_trig_name),
> + "%s-tx", netdev->name);
> + snprintf(priv->rx_led_trig_name, sizeof(priv->rx_led_trig_name),
> + "%s-rx", netdev->name);
I'm afraid that this is going to race against other code using trigger
name, so that's probabily needs a down_write(&led_cdev->trigger_lock),
which is a bit of a problem beacause that's static in led-triggers.c.
> + return NOTIFY_DONE;
> +}
> +
> +/* notifier block for netdevice event */
> +static struct notifier_block can_netdev_notifier __read_mostly = {
> + .notifier_call = can_led_notifier,
> +};
> +
> +static __init int can_led_init(void)
> +{
> + return register_netdevice_notifier(&can_netdev_notifier);
> +}
> +
> +static __exit void can_led_exit(void)
> +{
> + unregister_netdevice_notifier(&can_netdev_notifier);
> +}
> +
> +module_init(can_led_init);
> +module_exit(can_led_exit);
This breaks the driver when built as a module, as led.c is actually
linked together with can-dev. The solution is to get it on a module by
its own or just to call init/exit functions from can_dev.
Besides those points I like the idea of renaming the trigger if we can
find a clean way to do that, so I'll try to look at those point further
in the weekend.
Fabio
next prev parent reply other threads:[~2012-09-06 18:58 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
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 [this message]
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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