linux-kernel - Re: [RFC PATCH] can: m_can: Add driver for M

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Date:   Sun, 9 Jan 2022 00:25:03 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Brian Silverman <bsilver16384@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:CAN NETWORK DRIVERS" <linux-can@...r.kernel.org>,
        "open list:TEGRA ARCHITECTURE SUPPORT" <linux-tegra@...r.kernel.org>
Subject: Re: [RFC PATCH] can: m_can: Add driver for M_CAN hardware in NVIDIA
 devices

On 05.01.2022 16:25:09, Brian Silverman wrote:
> It's a M_TTCAN with some NVIDIA-specific glue logic and clocks. The
> existing m_can driver works with it after handling the glue logic.
> 
> The code is a combination of pieces from m_can_platform and NVIDIA's
> driver [1].
> 
> [1] https://github.com/hartkopp/nvidia-t18x-can/blob/master/r32.2.1/nvidia/drivers/net/can/mttcan/hal/m_ttcan.c
> 
> Signed-off-by: Brian Silverman <brian.silverman@...erivertech.com>

Thanks for your patch.

> ---
> I ran into bugs with the error handling in NVIDIA's m_ttcan driver, so I
> switched to m_can which has been much better. I'm looking for feedback
> on whether I should ensure rebasing hasn't broken anything, write up DT
> documentation, and submit this patch for real. The driver works great,
> but I've got some questions about submitting it.
> 
> question: This has liberal copying of GPL code from NVIDIA's
> non-upstreamed m_ttcan driver. Is that OK?

The header in the driver says it's GPLv2:

| https://github.com/hartkopp/nvidia-t18x-can/blob/master/r32.2.1/nvidia/drivers/net/can/mttcan/hal/m_ttcan.c#L5

So it's OK. You should copy the original copyright notice to your glue
driver, though.

> corollary: I don't know what any of this glue logic does. I do know the
> device doesn't work without it. I can't find any documentation of what
> these addresses do.

hmmm ok

> question: There is some duplication between this and m_can_platform. It
> doesn't seem too bad to me, but is this the preferred way to do it or is
> there another alternative?

You might merge this driver to the generic platform driver.

> question: Do new DT bindings need to be in the YAML format, or is the
> .txt one OK?

YAML

Please fix the checkpatch warning found by:

| ./scripts/checkpatch.pl --file drivers/net/can/m_can/m_can_tegra.c

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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