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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Tue, 10 Dec 2019 18:51:14 +0100
Message-ID: <CAK8P3a1cwoTbT3zsa-tfApwewDT1-ksHZs6_vkBYpKbgptsfjw@mail.gmail.com>
Subject: Re: [RFC 5/5] i3c: add i3cdev module to expose i3c dev in /dev
To:     Vitor Soares <Vitor.Soares@synopsys.com>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        linux-i3c@lists.infradead.org,
        Joao Pinto <Joao.Pinto@synopsys.com>,
        Boris Brezillon <bbrezillon@kernel.org>,
        gregkh <gregkh@linuxfoundation.org>,
        Wolfram Sang <wsa@the-dreams.de>,
        Mark Brown <broonie@kernel.org>
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On Tue, Dec 10, 2019 at 4:37 PM Vitor Soares <Vitor.Soares@synopsys.com> wrote:
>
> +/* IOCTL commands */
> +#define I3C_DEV_IOC_MAGIC      0x07
> +
> +struct i3c_ioc_priv_xfer {
> +       struct i3c_priv_xfer __user *xfers;     /* pointers to i3c_priv_xfer */
> +       __u32 nxfers;                           /* number of i3c_priv_xfer */
> +};
> +
> +#define I3C_IOC_PRIV_XFER      \
> +       _IOW(I3C_DEV_IOC_MAGIC, 30, struct i3c_ioc_priv_xfer)
> +
> +#define  I3C_IOC_PRIV_XFER_MAX_MSGS    42

This is not a great data structure for UAPI, please see
https://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground.git/tree/Documentation/core-api/ioctl.rst?h=compat-ioctl-endgame&id=927324b7900ee9b877691a8b237e272fabb21bf5

for some background. I'm planning to submit that documentation for
mainline integration soon.

     Arnd