Re: serial can or socket can ?

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 06/12/2012 03:44 PM, Oliver Hartkopp wrote:
> On 12.06.2012 14:55, bruce bushby wrote:
> 
>> Hi
>>
>> I wanted to confirm my understanding of "socketcan" in terms "slcan0" and "can0"
>>
> 
> 
> Ok, let's go ...
> 
>> I've been playing with a Beaglebone board the a usb-can adaptor from
>> mictronics.de:
>> http://www.mictronics.de/projects/usb-can-bus/
>> Purchased from:
>> http://shop.greenstage.co.nz/product/usb-can-bus-interface
>>
>> 1. Is my understanding correct that "slcan" will ALWAYS be used when
>> connecting a USB based CANBUS adapter?
> 
> 
> No.
> 
> The slcan driver provides a CAN network device for CAN interfaces that are
> controlled by the ASCII protocol first brought up by LAWICEL (www.can232.com,
> www.canusb.com). The slcan driver converts the ASCII frames to struct
> can_frame which is used in the Linux CAN subsystem (aka SocketCAN).
> 
> You may have a CAN device supporting the SLCAN protocol on RS232, USB-serial
> adapters, whatever.
> 
> See
> 
> http://lxr.linux.no/#linux+v3.4.2/drivers/net/can/Kconfig#L13
> 
> and
> 
> http://lxr.linux.no/#linux+v3.4.2/drivers/net/can/slcan.c#L99
> 
> There are CAN USB drivers in the tree, that do not use the SLCAN protocol:
> 
> http://lxr.linux.no/#linux+v3.4.2/drivers/net/can/usb/Kconfig
> 
> 
>>
>> I am able to bringup slcan0 using the following commands:
> 
> 
> Use this
> 
>> # slcan_attach -o -s6 /dev/ttyUSB0
>> attached tty /dev/ttyUSB0 to netdevice slcan0
> 
> 
> OR this
> 
>> # slcand ttyUSB0
> 
> 
> !
> 
> Running slcand and slcan_attach together doesn't make sense.
> 
> 
>> # ifconfig slcan0 up
>> # ifconfig slcan0
>> slcan0    Link encap:UNSPEC  HWaddr
>> 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
>>           UP RUNNING NOARP  MTU:16  Metric:1
>>           RX packets:0 errors:0 dropped:0 overruns:0 frame:0
>>           TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
>>           collisions:0 txqueuelen:10
>>           RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
>>
>> #
>>
>>
>> 2. AM335x has an internal D_CAN, but the Beaglebone is missing any CAN
>> transceiver...would the lack of the transceiver prevent the kernel
>> from creating the "can0" device?

As Oliver said, you need a platform device definition in your board file
and a kernel that supports the d_can hardware. You can use David
Miller's net-next/master tree.

regards, Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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