linux-kernel - Re: of alloc_canxl

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Message-ID: <2540406e-8da3-4cb8-bd1a-30271dd6cc67@hartkopp.net>
Date: Fri, 13 Sep 2024 21:51:39 +0200
From: Oliver Hartkopp <socketcan@...tkopp.net>
To: "Dr. David Alan Gilbert" <linux@...blig.org>, mkl@...gutronix.de
Cc: linux-can@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: of alloc_canxl_skb

Hi David,

On 13.09.24 16:03, Dr. David Alan Gilbert wrote:

>    I'm doing some deadcode hunting and noticed that
> 
>    alloc_canxl_skb in drivers/net/can/dev/skb.c
> 
> looks unused in the main kernel tree; is that expected?
> I see it was added back in 2022 by
>    fb08cba12b52 ("can: canxl: update CAN infrastructure for CAN XL frames")
> 
> I know almost exactly nothing about CAN, so I thought it best
> to ask!

I created some slides so that you can get an introduction to the 
different CAN protocols CAN CC (aka Classical CAN), CAN FD and CAN XL:

https://github.com/linux-can/can-doc/tree/master/presentations

The introduction of the CAN XL support lead to some clean up and rework 
also for the former alloc_can_skb() and alloc_canfd_skb() helpers.

The function is currently not in use in net/can/raw.c as it is only 
needed when a CAN XL frame is received from read hardware. But the patch 
also contains the definition of ETH_P_CANXL to already handle CAN XL 
frames properly inside the Linux kernel and e.g. for WireShark 4.4.

There are currently some CAN XL IP cores in development (see attached 
picture with an FPGA based IP core) and I am working on the kernel 
infrastructure (e.g. bitrate configuration enhancements) on this board. 
So alloc_canxl_skb() is already in use on my desk and there will be some 
more stuff showing up soon ;-)

Best regards,
Oliver
Download attachment "DE1_SoC_FPGA_working_setup.jpg" of type "image/jpeg" (236146 bytes)