On 06.09.2012 20:59, Fabio Baltieri wrote:
> 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.di...@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.
Do you think, this is really a problem?
If a driver decides not to use the can-dev framework it has to implement own
solutions or just adopt can-dev.
Regards,
Oliver
>
> Is there any way to register a notifier which fires only for devices
> registered with devm_can_led_init?
>
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