From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wolfgang Grandegger <wg@grandegger.com>
Subject: Re: [RFC PATCH] can: dev: update rx state in the can_get_echo_skb()
Date: Thu, 28 Jun 2012 12:59:35 +0200
Message-ID: <4FEC3917.5020905@grandegger.com>
References: <1340876540-27840-1-git-send-email-jason77.wang@gmail.com>
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To: Hui Wang <jason77.wang@gmail.com>
Cc: mkl@pengutronix.de, shawn.guo@linaro.org, linux-can@vger.kernel.org

On 06/28/2012 11:42 AM, Hui Wang wrote:
> After a loopback packet is routed to rx interface, we forget to update
> rx state both in the can_get_echo_skb() and in the controller specific
> drivers, as a result, after we sent a loopback packet and executed
> ifconfig, following state is outputed:
> can0      Link encap:UNSPEC  HWaddr 00-00-00-00-<snip>
>           UP RUNNING NOARP  MTU:16  Metric:1
>           RX packets:0 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:1 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:10
>           RX bytes:0 (0.0 B)  TX bytes:4 (4.0 B)
> 
> We add rx state update in the can_get_echo_skb() to solve this
> problem.

Well...

> Cc: linux-can@vger.kernel.org
> Cc: Marc Kleine-Budde <mkl@pengutronix.de>
> Cc: Wolfgang Grandegger <wg@grandegger.com>
> Cc: Shawn Guo <shawn.guo@linaro.org>
> Signed-off-by: Hui Wang <jason77.wang@gmail.com>
> ---
> I don't know if it is designed like that on purpose, please instruct
> me if i am wrong.
> 
> I use following commands to let flexcan to work in the loopback mode:
> %>ip link set can0 type can bitrate 125000
> %>ip link set can0 type can loopback on
> %>ip link set can0 up
> And send a packet:
> %>cantest can0 123#AABBCCDD
> When i check net device state, i found tx doesn't equal rx:
> %>ifconfig
> can0      Link encap:UNSPEC  HWaddr 00-00-00-00-<snip>
>           UP RUNNING NOARP  MTU:16  Metric:1
>           RX packets:0 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:1 errors:0 dropped:0 overruns:0 carrier:0

This means that one message has successfully been sent to the *real* CAN
bus.

>           collisions:0 txqueuelen:10
>           RX bytes:0 (0.0 B)  TX bytes:4 (4.0 B)
> 
>>>From my understanding, i suppose it should be:
> can0      Link encap:UNSPEC  HWaddr 00-00-00-00-<snip>
>           UP RUNNING NOARP  MTU:16  Metric:1
>           RX packets:1 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:1 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:10 
>           RX bytes:4 (4.0 B)  TX bytes:4 (4.0 B)

Why, you have not received any message from the CAN bus. If you want to
count looped back messages, it should be:

          RX packets:1 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2 errors:0 dropped:0 overruns:0 carrier:0

Wolfgang.