On 27.07.2022 17:55:10, Dario Binacchi wrote: > Hello Marc, > > On Wed, Jul 27, 2022 at 1:31 PM Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> wrote: > > > > On 26.07.2022 23:02:16, Dario Binacchi wrote: > > > It allows to set the bit time register with tunable values. > > > The setting can only be changed if the interface is down: > > > > > > ip link set dev can0 down > > > ethtool --set-tunable can0 can-btr 0x31c > > > ip link set dev can0 up > > > > As far as I understand, setting the btr is an alternative way to set the > > bitrate, right? > > I thought of a non-standard bitrate or, in addition to the bitrate, the > possibility of enabling some specific CAN controller options. Maybe Oliver > could help us come up with the right answer. > > This is the the slcan source code: > https://github.com/linux-can/can-utils/blob/cad1cecf1ca19277b5f5db39f8ef6f8ae426191d/slcand.c#L331 > btr case cames after speed but they don't seem to be considered alternative. > > > I don't like the idea of poking arbitrary values into a > > hardware from user space. > > However this is already possible through the slcand and slcan_attach > applications. > Furthermore, the driver implements the LAWICEL ASCII protocol for CAN > frame transport over serial lines, > and this is one of the supported commands. > > > > > Do you have a use case for this? > > I use the applications slcand and slcan_attach as a reference, I try to make the > driver independent from them for what concerns the CAN setup. And the bit time > register setting is the last dependency. Ok - We avoided writing bit timing registers from user space into the hardware for all existing drivers. If there isn't a specific use case, let's skip this patch. If someone comes up with a use case we can think of a proper solution. Marc -- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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