Re: [RFC PATCH 00/14] can: netlink: add CAN XL

[Vincent Mailhol <mailhol.vincent@wanadoo.fr>]

On 11/11/2024 at 23:08, Oliver Hartkopp wrote:
> Hello Vincent!
>
> Very impressive! Thanks for the effort.
> Together with the example in the dummyxl driver it should become quite 
> easy to integrate the netlink API into my XCANB driver hack for testing.
>
> Picking up the dummyxl driver I wonder if it would make sense to 
> mainline this driver probably as can_nltest driver?!?
> Of course this driver should be disabled or combined with some kernel 
> testing Kconfig stuff. But is it a great testing tool.

Thanks. I do not recall similar things in the netdev subtree. I wonder 
what would be the idiomatic way to introduce such netlink test driver.

@Marc, any thoughts on this?

> From what I can see with the bitrate and tdc configurations the 
> extension for CAN XL is ok.
>
> If you take a look at this manual
>
> https://github.com/linux-can/can-doc/blob/master/x_can/xcan_user_manual_v350.pdf 
>
>
> on page 268/304 you will find the PWM configuration which consists of 
> three values with 6 bits each. I assume this to be similar in all CAN 
> XL controllers.
>
> The PWM feature switches the physical layer for a CAN XL transceiver 
> in the CAN XL data phase. This is a weird feature to do some PWM on 
> the controllers' TX data pin to be able to switch the physical layer 
> while maintaining the CAN transceiver package with 8 pin layout.
>
> Additionally to this PWM configuration register, the PWM CAN XL 
> transceiver switch feature has to be enabled similar to the way we 
> enable 'fd on' or 'xl on' today.
>
> You can see this bit called XLTR in the Operating Mode section on page 
> 269/304 and 270/304 .
>
> E.g. that might be named 'xltrx [on|off]' (default off)
Thanks for the information and the link to the documentation. I will 
also try to see what ISO 11898-1:2024 has to say on the topic. Just be 
patient on this and do not worry if I give no signal for a couple weeks.

Vincent Mailhol