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SubjectRe: [RFC PATCH 04/13] can: slcan: use CAN network device driver API
Hi Marc,

On Tue, Jun 7, 2022 at 1:13 PM Marc Kleine-Budde <mkl@pengutronix.de> wrote:
>
> On 07.06.2022 11:47:43, Dario Binacchi wrote:
> > As suggested by commit [1], now the driver uses the functions and the
> > data structures provided by the CAN network device driver interface.
> >
> > There is no way to set bitrate for SLCAN based devices via ip tool, so
> ^^^^^^^^^^^^^^^
> Currently the driver doesn't implement a way

Ok, I'll do it.

>
> > you'll have to do this by slcand/slcan_attach invocation through the
> > -sX parameter:
> >
> > - slcan_attach -f -s6 -o /dev/ttyACM0
> > - slcand -f -s8 -o /dev/ttyUSB0
> >
> > where -s6 in will set adapter's bitrate to 500 Kbit/s and -s8 to
> > 1Mbit/s.
> > See the table below for further CAN bitrates:
> > - s0 -> 10 Kbit/s
> > - s1 -> 20 Kbit/s
> > - s2 -> 50 Kbit/s
> > - s3 -> 100 Kbit/s
> > - s4 -> 125 Kbit/s
> > - s5 -> 250 Kbit/s
> > - s6 -> 500 Kbit/s
> > - s7 -> 800 Kbit/s
> > - s8 -> 1000 Kbit/s
> >
> > In doing so, the struct can_priv::bittiming.bitrate of the driver is not
> > set and since the open_candev() checks that the bitrate has been set, it
> > must be a non-zero value, the bitrate is set to a fake value (-1) before
> > it is called.
>
> What does
>
> | ip --details -s -s link show
>
> show as the bit rate?

# ip --details -s -s link show dev can0
can0: <NOARP,UP,LOWER_UP> mtu 16 qdisc pfifo_fast state UP mode
DEFAULT group default qlen 10
link/can promiscuity 0 minmtu 0 maxmtu 0
can state ERROR-ACTIVE restart-ms 0
bitrate 500000 sample-point 0.875
tq 41 prop-seg 20 phase-seg1 21 phase-seg2 6 sjw 1
slcan: tseg1 2..256 tseg2 1..128 sjw 1..128 brp 1..256 brp-inc 1
clock 24000000
re-started bus-errors arbit-lost error-warn error-pass bus-off
0 0 0 0 0 0
numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
RX: bytes packets errors dropped overrun mcast
292 75 0 0 0 0
RX errors: length crc frame fifo missed
0 0 0 0 0
TX: bytes packets errors dropped carrier collsns
0 0 0 0 0 0
TX errors: aborted fifo window heartbeat transns
0 0 0 0 1

And after applying your suggestions about using the CAN framework
support for setting the fixed bit rates (you'll
find it in V2), this is the output instead:

# ip --details -s -s link show dev can0
5: can0: <NOARP,UP,LOWER_UP> mtu 16 qdisc pfifo_fast state UP mode
DEFAULT group default qlen 10
link/can promiscuity 0 minmtu 0 maxmtu 0
can state ERROR-ACTIVE restart-ms 0
bitrate 500000
[ 10000, 20000, 50000, 100000, 125000, 250000,
500000, 800000, 1000000 ]
clock 0
re-started bus-errors arbit-lost error-warn error-pass bus-off
0 0 0 0 0 0
numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
RX: bytes packets errors dropped overrun mcast
37307 4789 0 0 0 0
RX errors: length crc frame fifo missed
0 0 0 0 0
TX: bytes packets errors dropped carrier collsns
7276 988 0 0 0 0
TX errors: aborted fifo window heartbeat transns
0 0 0 0 1

Thanks and regards,
Dario

>
> 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 |



--

Dario Binacchi

Embedded Linux Developer

dario.binacchi@amarulasolutions.com

__________________________________


Amarula Solutions SRL

Via Le Canevare 30, 31100 Treviso, Veneto, IT

T. +39 042 243 5310
info@amarulasolutions.com

www.amarulasolutions.com

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