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From:   Dario Binacchi <dario.binacchi@amarulasolutions.com>
Date:   Tue, 26 Jul 2022 14:14:12 +0200
Message-ID: <CABGWkvpQ_5Yz=B0Q=qJGd1vkysntV=449wbv43opvO6=UDrAJw@mail.gmail.com>
Subject: Re: [PATCH v2 0/6] can: slcan: extend supported features (step 2)
To:     Marc Kleine-Budde <mkl@pengutronix.de>
Cc:     linux-kernel@vger.kernel.org, michael@amarulasolutions.com,
        Amarula patchwork <linux-amarula@amarulasolutions.com>,
        Jeroen Hofstee <jhofstee@victronenergy.com>,
        Oliver Hartkopp <socketcan@hartkopp.net>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Wolfgang Grandegger <wg@grandegger.com>,
        linux-can@vger.kernel.org, netdev@vger.kernel.org
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Hello Marc,

On Mon, Jul 25, 2022 at 3:25 PM Marc Kleine-Budde <mkl@pengutronix.de> wrote:
>
> On 25.07.2022 08:54:13, Dario Binacchi wrote:
> > With this series I try to finish the task, started with the series [1],
> > of completely removing the dependency of the slcan driver from the
> > userspace slcand/slcan_attach applications.
> >
> > The series, however, still lacks a patch for sending the bitrate setting
> > command to the adapter:
> >
> > slcan_attach -b <btr> <dev>
> >
> > Without at least this patch the task cannot be considered truly completed.
> >
> > The idea I got is that this can only happen through the ethtool API.
> > Among the various operations made available by this interface I would
> > have used the set_regs (but only the get_regs has been developed), or,
> > the set_eeprom, even if the setting would not be stored in an eeprom.
> > IMHO it would take a set_regs operation with a `struct ethtool_wregs'
> > parameter similar to `struct ethtool_eeprom' without the magic field:
>
> This doesn't feel right.
>
> > struct ethtool_wregs {
> >       __u32   cmd;
> >       __u32   offset;
> >       __u32   len;
> >       __u8    data[0];
> > };
> >
> > But I am not the expert and if there was an alternative solution already
> > usable, it would be welcome.
>
> Have a look at the get/set_tunable() callback:
>
> | https://elixir.bootlin.com/linux/latest/source/include/linux/ethtool.h#L575
>
> You probably have to add a new tunable. Here you'll find the people and
> commits that changed the tunable:
>
> | https://github.com/torvalds/linux/blame/master/include/uapi/linux/ethtool.h#L229
>
> It's usually worth including them in an RFC patch series where you add a
> new tunable and make use of it in the slcan driver.

Thank you very much for the suggestions.
Regards,

Dario
>
> 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 |


-- 

Dario Binacchi

Embedded Linux Developer

dario.binacchi@amarulasolutions.com

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