Am Freitag, den 09.07.2021, 14:00 +0200 schrieb Vincent MAILHOL: > On Wed. 7 Jul 2021 at 19:45, Joshua Quesenberry <engnfrc@xxxxxxxxx> wrote: > > Good Afternoon, > > > > Do any of you know a way to check what options are valid when setting up a > > CAN device with the ip link commands, either from bash or through C++? I'm > > working on a piece of code that will get used on systems with varying CAN > > drivers and for instance one of them doesn't support CAN-FD, so how would I > > be able to know that setting the fd flag or dbitrate value would fail before > > calling the setup command and seeing it fail? > > I would suggest to use: > > ip --details link show can0 > > You can then parse the results to check if the data bitrate > information is present. If so, it means that FD is supported. > Also, the output might be easier to parse if formatted in json: > > ip --details --json --pretty link show can0 > > Alternatively, instead of using the command line, you might > prefer to directly use the kernel netlink interface to directly > retrieve the different modes supported by the controller. > You can refer to iproute2 source code for the how-to: > https://git.kernel.org/pub/scm/network/iproute2/iproute2.git/tree/ip/iplink_can.c#n282 > Unfortunately the netlink kernel interface gives access only to the IFLA_CAN_CTRLMODE data which boils down to an access of the netdev_priv(dev)- >priv->ctrlmode flags set in the driver (see also in a Linux tree under drivers/net/can/dev/netlink.c). But the "ctrlmode" flags represent only the current setup. So you can see if CAN-FD mode is currently enabled. But I think the thread opener wants to know in advance if the kernel gives us the information what modes a certain driver supports. That is encoded in netdev_priv(dev)->priv->ctrlmode_supported and netdev_priv(dev)->priv- >ctrlmode_static. But for these flags there is no netlink interface to interrogate that settings at the moment. So you can't see in advance if a CAN driver would support for instance triple- sampling or the CAN_CTRLMODE_CC_LEN8_DLC mode. To know it you must try to set such option atm. I think. Best regards, Stefan
