Re: [PATCH v2] can: propagate CAN device capabilities via ml_priv

[Vincent Mailhol <mailhol@kernel.org>]

Hi Oliver,

Happy new year to you and to all the members of the CAN mailing
list!(and also to Arnd who is listed in CC ;))

On 31/12/2025 at 17:51, Oliver Hartkopp wrote:
> Commit 1a620a723853 ("can: raw: instantly reject unsupported CAN frames")
> caused a sequence of dependency and linker fixes starting with commit
> cb2dc6d2869a ("can: Kconfig: select CAN driver infrastructure by default").
> 
> The entire problem was caused by the requirement that a new network layer
> feature needed to know about the protocol capabilities of the CAN devices.
> Instead of accessing CAN device internal data structures which caused the
> dependency problems this patch introduces capabilty information into the
> CAN specific ml_priv data which is accessible from both sides.
> 
> With this change the CAN network layer can check the required features and
> the decoupling of the driver layer and network layer is restored.
> Therefore the Kconfig and Makefile changes/fixes are reverted too.
> 
> Fixes: 1a620a723853 ("can: raw: instantly reject unsupported CAN frames")
> Fixes: cb2dc6d2869a ("can: Kconfig: select CAN driver infrastructure by default")
> Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
> ---
>  drivers/net/can/Kconfig       |  7 ++++--
>  drivers/net/can/Makefile      |  2 +-
>  drivers/net/can/dev/Makefile  |  5 ++--
>  drivers/net/can/dev/dev.c     | 19 +++++++++++++++
>  drivers/net/can/dev/netlink.c |  1 +
>  drivers/net/can/vcan.c        | 15 ++++++++++++
>  drivers/net/can/vxcan.c       | 15 ++++++++++++
>  include/linux/can/can-ml.h    | 24 +++++++++++++++++++
>  include/linux/can/dev.h       |  8 +------
>  net/can/raw.c                 | 45 ++++-------------------------------

This is a huge patch. I think it should be split in smaller pieces with
the reverts and the new code in different patches. What I would suggest
is to split it in 3 like this:

  Patch #1: revert 1a620a723853 ("can: raw: instantly reject unsupported
            CAN frames") and all the Kconfig subsequent fix attempts.

  Patch #2: Introduce the new logic.

  Patch #3: reintroduce 1a620a723853.


Reverting 1a620a723853 and reintroducing it later is kind of necessary
to have each patch of the series in a working state.


Yours sincerely,
Vincent Mailhol