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

[Oliver Hartkopp <socketcan@hartkopp.net>]

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'.

> Or read out the occupied size of it
> to get the mumber of CAN frames waiting for transmission?


I'll take a look, if there's a programming interface to get this value.
Or is this request obsolete now after my answer above?

Regards,
Oliver