Re: "Blessed" Version

[Yegor Yefremov <yegor_sub1@visionsystems.de>]

On 13.10.2012 12:17, Oliver Hartkopp wrote:
> Hello Stuart,
> 
> On 11.10.2012 21:09, Stuart Statman wrote:
> 
>> Strangely enough, just yesterday we made a decision to migrate CAN hardware
>> that reduced the urgency of my question.
>>
>> However, it does bring up another question.
>>
>> I've been using slcand and "ip link set xxx up" for a piece of hardware that
>> uses the slcan protocol. I'm pretty happy with how it's working, but I'd be
>> happier if it was compatible with the can_if script that's in the utilities. I
>> could write my own version of can_if that just does the right things for
>> slcan, but it does open up a few questions :
>>
>> 1. What is slcan anyway, and why is it not handled like the other drivers?
> 
> 
> The SLCAN driver adds the support for (usually low cost) simple CAN interfaces
> that transfer the CAN frames via some ASCII based protocol.
> 
> As these interfaces are attached via the serial line (RS232 or USB/serial) the
> slcan driver implements a 'serial line discipline' as you might know from
> early internet times where you used a modem to connect the internet.
> 
> In that modem case IP network packets have been transmitted through the serial
> line, after the modem has been set up and connected (-> ppp daemon).
> Once switching the 'line discipline' IP packets are tranferred via serial.
> 
> Same here with SLCAN:
> 
> First the SLCAN adapter needs to be configured (speed 'S') and opened 'O' and
> then the line discipline is switched to transfer CAN frames with the ASCII
> protocol (slcan_attach, slcand).
> 
> As this is a completely different CAN adapter configuration interface the
> CAN-DEV framework therefore can not be used and the 'ip link set' stuff does
> not work for SLCAN devices.
> 
>> 2. Is there a can_if style script that already handles slcan?
> 
> 
> We have extended the can_if script for slcan at Volkswagen and also extended
> the slcand to do some of the setup from slcan_attach (e.g. for the CAN
> bitrate). I don't know the exact state of these extensions and if it works
> stable in all environments (udev, ...). But if you like, i can sent it to you
> and you may check if it fit's your needs and if it's worth to merge it with
> the can-utils.

Please share the changes for can_if and related stuff. I was already looking for this.

Best regards,
Yegor