Re: What are you doing if the TX buffer overflows?

[Wolfgang Grandegger <wg@grandegger.com>]

On 09/17/2012 09:19 PM, Oliver Hartkopp wrote:
> Hello Heinz,
> 
> On 17.09.2012 15:58, Heinz-Jürgen Oertel wrote:
> 
>>
>> is there a way to empty the tx buffer ?
> 
> 
> Usually the buffer does not get empty due to a problem of the CAN controller
> and/or the CAN network.
> 
> So even if you could flush the queue the CAN controller is probably still
> stuck with his processed frame.
> 
> Setting the interface to DOWN and UP again re-initializes the CAN controller
> and flushes all the queues.
> 
> This would work - but all open sockets would get a notification of the
> interface went down.
> 
> Btw. IIRC there's a IFLA_CAN_RESTART functionality to kick the CAN controller
> if it got stuck. It can by triggered by a netlink message. This is the same
> configuration interface that's used to set the bittiming:
> 
> http://lxr.linux.no/#linux+v3.5.4/include/linux/can/netlink.h#L103
> 
> But i have currently no source code example as i always use the 'ip' tool from
> the iproute2 package to configure my CAN interfaces:
> 
> http://lxr.linux.no/#linux+v3.5.4/Documentation/networking/can.txt#L646
> 
> Following that documentation
> 
> 	ip link set can0 type can restart
> 
> should do it for 'can0'.

No, this does only works if a bus-off is pending. See:

http://lxr.linux.no/#linux+v3.5.4/drivers/net/can/dev.c#L413

Well, the name IFLA_CAN_RESTART is not really well chosen.

Wolfgang.