linux-kernel - Re: [PATCH 0/9] can: netlink: add CAN XL

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Message-ID: <a729eeda-22d8-4f3e-bb6b-0cd2f3a06d2a@kernel.org>
Date: Sat, 18 Oct 2025 00:40:22 +0900
From: Vincent Mailhol <mailhol@...nel.org>
To: Marc Kleine-Budde <mkl@...gutronix.de>
Cc: Oliver Hartkopp <socketcan@...tkopp.net>,
 Stéphane Grosjean <stephane.grosjean@...-networks.com>,
 Robert Nawrath <mbro1689@...il.com>, Minh Le <minh.le.aj@...esas.com>,
 Duy Nguyen <duy.nguyen.rh@...esas.com>, linux-can@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/9] can: netlink: add CAN XL

On 17/10/2025 at 22:53, Marc Kleine-Budde wrote:
> On 13.10.2025 20:01:22, Vincent Mailhol wrote:
>> Following all the refactoring on the CAN netlink done in series [1],
>> [2] and [3], this is now time to finally introduce the CAN XL netlink
>> interface.
>>
>> Similarly to how CAN FD reuses the bittiming logic of Classical CAN,
>> CAN XL also reuses the entirety of CAN FD features, and, on top of
>> that, adds new features which are specific to CAN XL.
>>
>> Patch #1 adds a check in can_dev_dropped_skb() to drop CAN FD frames
>> when CAN FD is turned off.
>>
>> Patch #2 adds CAN_CTRLMODE_RESTRICTED. Note that contrary to the other
>> CAN_CTRL_MODE_XL_* that are introduced in the later patches, this
>> control mode is not specific to CAN XL. The nuance is that because
>> this restricted mode was only added in ISO 11898-1:2024, it is made
>> mandatory for CAN XL devices but optional for other protocols. This is
>> why this patch is added as a preparation before introducing the core
>> CAN XL logic.
> 
> What about merging patches 1+2 now?

If patch 1 had to be squashed, it should probably be in patch 3
"can: netlink: add initial CAN XL support". The MTU workaround as
introduced in patch 1 does not share any of the logic of the
CAN_CTRLMODE_RESTRICTED as introduced in patch 2. Patch 1 is really
just a preparation for CAN XL. You could remove patch 2 from the
series and it will still work (aside from missing one of ISO mandatory
features). Remove patch 1, and the thing breaks apart because it is
required by patch 3.

If I were to squash 1 and 2, I am not sure how I would describe those
two different changes in a single patch message.


Yours sincerely,
Vincent Mailhol