linux-kernel - RE: [EXT] Re: [PATCH] can: dev: clean up CAN ctrlmode when close CAN device

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Date:   Wed, 10 Apr 2019 07:55:40 +0000
From:   Joakim Zhang <qiangqing.zhang@....com>
To:     Marc Kleine-Budde <mkl@...gutronix.de>,
        "wg@...ndegger.com" <wg@...ndegger.com>,
        "davem@...emloft.net" <davem@...emloft.net>
CC:     dl-linux-imx <linux-imx@....com>,
        "linux-can@...r.kernel.org" <linux-can@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [EXT] Re: [PATCH] can: dev: clean up CAN ctrlmode when close CAN
 device


> -----Original Message-----
> From: Marc Kleine-Budde <mkl@...gutronix.de>
> Sent: 2019年4月10日 15:19
> To: Joakim Zhang <qiangqing.zhang@....com>; wg@...ndegger.com;
> davem@...emloft.net
> Cc: dl-linux-imx <linux-imx@....com>; linux-can@...r.kernel.org;
> netdev@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: [EXT] Re: [PATCH] can: dev: clean up CAN ctrlmode when close CAN
> device
> 
> On 4/10/19 8:27 AM, Joakim Zhang wrote:
> > CAN driver always writes registers according to "ctrlmode", and now
> > CAN framework will keep CAN ctrlmode after device closed.
> >
> > e.g. with following sequences:
> > 1)ip link set can0 type can bitrate 1000000 loopback on 2)ip link set
> > can0 up 3)ip link set can0 down 4)ip link set can0 type can bitrate
> > 1000000 5)ip link set can0 up
> >
> > After this sequence, we may want to test loopback for the first time
> > and not to test loopback second time. However, CAN device still keep
> > "ctrlmode" as loopback on.
> 
> Then you should configure loopback off in userspace.

 Got it. Thank you.

> > This patch intends to clean up CAN ctrlmode when close CAN device. We
> > can set which ctrlmode we need when open CAN device again.
> 
> Consider a CANFD device, where CANFD has been enabled. It will feel very
> weird if the interface looses the CANFD property by just a ifdown; ifup.

Yes, you are right. But fd mode should compatible with normal can. When I want to switch to normal can from fd mode.
You mean that we should configure fd off in userspace as we may write some specific registers only by fd mode?


Best Regards,
Joakim Zhang
> >
> > Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
> > ---
> >  drivers/net/can/dev.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c index
> > c05e4d50d43d..4f69a8f16ba3 100644
> > --- a/drivers/net/can/dev.c
> > +++ b/drivers/net/can/dev.c
> > @@ -870,6 +870,7 @@ void close_candev(struct net_device *dev)
> >  	struct can_priv *priv = netdev_priv(dev);
> >
> >  	cancel_delayed_work_sync(&priv->restart_work);
> > +	priv->ctrlmode = 0;
> >  	can_flush_echo_skb(dev);
> >  }
> >  EXPORT_SYMBOL_GPL(close_candev);
> >
> 
> Marc
> 
> --
> Pengutronix e.K.                  | Marc Kleine-Budde           |
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