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SubjectRe: [PATCH v5 0/7] can: refactoring of can-dev module and of Kbuild
Hi Vincent,

On 07.06.22 04:49, Vincent MAILHOL wrote:
> On Tue. 7 Jun. 2022 at 04:43, Oliver Hartkopp <> wrote:

>>> |
>>> +-> All other CAN devices not relying on RX offload
>>> |
>>> +-> CAN rx offload
>> Is this still true in patch series 5?
>> If I understood it correctly CONFIG_CAN_BITTIMING and
>> CONFIG_CAN_RX_OFFLOAD can be enabled by the user and
>> (alternatively/additionally) the selection of "flexcan, m_can, mcp251xfd
>> and ti_hecc" enables CONFIG_CAN_RX_OFFLOAD too.
>> Right?
> Yes, this is correct. Maybe what troubles you is the meaning of the
> "x --> y" arrow in the graph. I said it denotes that "y depends on x".
> Here "depends on" has a loose meaning. It translates to either:
> * Feature Y is encapsulated in Kbuild by some "if X/endif" and won't
> show up unless X is selected.
> * Feature Y has a "selects X" tag and will forcibly enable X if selected.
> CONFIG_CAN_*CALC*_BITTIMING is on the left side of an arrow starting
> from CONFIG_CAN_NETLINK so it "depends" on CONFIG_CAN_NETLINK. On the
> other hand, CONFIG_CAN_*CALC*_BITTIMING does not have any arrow
> starting from it so indeed, it can be enabled by the user
> independently of the other features as long as CONFIG_CAN_NETLINK is
> selected.


> CONFIG_CAN_RX_OFFLOAD is also on the left side of an arrow starting
> from CONFIG_CAN_NETLINK. Furthermore, there is an arrow starting from
> CONFIG_CAN_RX_OFFLOAD going to the "rx offload drivers". So those
> drivers need CONFIG_CAN_RX_OFFLOAD (which is implemented using the
> be selected independently of the "rx offload drivers" as long as its
> CONFIG_CAN_NETLINK dependency is met.
> So I think that the diagram is correct. Maybe rephrasing the cover
> letter as below would address your concerns?
I applied your series and played with the options and it works like
charm - and as expected.

But the point remains that from your figure I would still assume that
the M_CAN driver would only show up when CONFIG_CAN_RX_OFFLOAD was
selected by the user.

But the current (good) implementation shows *all* drivers and selects
CONFIG_CAN_RX_OFFLOAD when e.g. M_CAN is selected.

So what about:

+-> CAN Device Drivers
+-> software/virtual CAN device drivers
| (at time of writing: slcan, vcan, vxcan)
+-> hardware CAN device drivers with Netlink support
symbol: CONFIG_CAN_NETLINK (matches previous CONFIG_CAN_DEV)
+-> CAN bit-timing calculation (optional for all drivers)
+-> CAN rx offload (optional but selected by some drivers)
+-> CAN devices drivers
(some may select CONFIG_CAN_RX_OFFLOAD)

(I also added 'hardware' to CAN device drivers with Netlink support) to
have a distinction to 'software/virtual' CAN device drivers)

At least this would help me to understand the new configuration setup.

Best regards,

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