On 4/10/19 9:55 AM, Joakim Zhang wrote: > >> -----Original Message----- >> From: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> >> Sent: 2019年4月10日 15:19 >> To: Joakim Zhang <qiangqing.zhang@xxxxxxx>; wg@xxxxxxxxxxxxxx; >> davem@xxxxxxxxxxxxx >> Cc: dl-linux-imx <linux-imx@xxxxxxx>; linux-can@xxxxxxxxxxxxxxx; >> netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx >> 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. CANFD was just an example. Take CAN_CTRLMODE_ONE_SHOT as another example. You don't want your network device settings to vanish if you switch the interface off and on again. > 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? Whatever mode you enable via user space use user space to disable them again. Marc -- Pengutronix e.K. | Marc Kleine-Budde | Industrial Linux Solutions | Phone: +49-231-2826-924 | Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de |
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