linux-kernel - Re: [RFC PATCH 1/9] ntsync: Introduce the ntsync driver and character device.

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Date: Wed, 24 Jan 2024 08:38:52 +0100
From: "Arnd Bergmann" <arnd@...db.de>
To: "Elizabeth Figura" <zfigura@...eweavers.com>,
 "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
 linux-kernel@...r.kernel.org, linux-api@...r.kernel.org
Cc: wine-devel@...ehq.org,
 André Almeida <andrealmeid@...lia.com>,
 "Wolfram Sang" <wsa@...nel.org>, "Arkadiusz Hiler" <ahiler@...eweavers.com>,
 "Peter Zijlstra" <peterz@...radead.org>
Subject: Re: [RFC PATCH 1/9] ntsync: Introduce the ntsync driver and character device.

On Wed, Jan 24, 2024, at 01:40, Elizabeth Figura wrote:
> ntsync uses a misc device as the simplest and least intrusive uAPI interface.
>
> Each file description on the device represents an isolated NT instance, intended
> to correspond to a single NT virtual machine.
>
> Signed-off-by: Elizabeth Figura <zfigura@...eweavers.com>

I'm looking at the ioctl interface to ensure it's well-formed.

Your patches look ok from that perspective, but there are a
few minor things I would check for consistency here:

> +
> +static const struct file_operations ntsync_fops = {
> +	.owner		= THIS_MODULE,
> +	.open		= ntsync_char_open,
> +	.release	= ntsync_char_release,
> +	.unlocked_ioctl	= ntsync_char_ioctl,
> +	.compat_ioctl	= ntsync_char_ioctl,
> +	.llseek		= no_llseek,
> +};

The .compat_ioctl pointer should point to compat_ptr_ioctl()
since the actual ioctl commands all take pointers instead
of interpreting the argument as a number.

On x86 and arm64 this won't make a difference as compat_ptr()
is a nop.

     Arnd