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Date:   Mon, 14 Jun 2021 20:18:09 +0300
From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Arnd Bergmann <arnd@kernel.org>
Cc:     Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        "Lad, Prabhakar" <prabhakar.csengg@gmail.com>,
        Eduardo Valentin <edubezval@gmail.com>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Vaibhav Gupta <vaibhavgupta40@gmail.com>,
        Liu Shixin <liushixin2@huawei.com>,
        Jacopo Mondi <jacopo+renesas@jmondi.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
        linux-staging@lists.linux.dev
Subject: Re: [PATCH v3 7/8] media: subdev: fix compat_ioctl32
Message-ID: <YMePUYfDzdsErRab@pendragon.ideasonboard.com>
References: <20210614103409.3154127-1-arnd@kernel.org>
 <20210614103409.3154127-8-arnd@kernel.org>
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In-Reply-To: <20210614103409.3154127-8-arnd@kernel.org>
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Hi Arnd,

Thank you for the patch.

On Mon, Jun 14, 2021 at 12:34:08PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> The adv7842 and si4713 drivers each define one private ioctl command that
> are handled through the subdev_ioctl() helpers, but that don't work in

s/don't/doesn't/

> compat mode because this does not handle private ioctl commands.
> 
> The compat_ioctl32 callback for subdevs has outdated calling conventions,
> but as there are no users of that, it is easy to change the function
> pointer type and the caller to make it behave the same way as the normal
> ioctl callback and hook in the two drivers that need no argument
> conversion.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  drivers/media/i2c/adv7842.c           |  3 +++
>  drivers/media/radio/si4713/si4713.c   |  3 +++
>  drivers/media/v4l2-core/v4l2-subdev.c | 19 ++++++++++++++++---
>  include/media/v4l2-subdev.h           |  3 +--
>  4 files changed, 23 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/media/i2c/adv7842.c b/drivers/media/i2c/adv7842.c
> index 78e61fe6f2f0..cd6df4f52f33 100644
> --- a/drivers/media/i2c/adv7842.c
> +++ b/drivers/media/i2c/adv7842.c
> @@ -3293,6 +3293,9 @@ static const struct v4l2_ctrl_ops adv7842_ctrl_ops = {
>  static const struct v4l2_subdev_core_ops adv7842_core_ops = {
>  	.log_status = adv7842_log_status,
>  	.ioctl = adv7842_ioctl,
> +#ifdef CONFIG_COMPAT
> +	.compat_ioctl32 = adv7842_ioctl,
> +#endif
>  	.interrupt_service_routine = adv7842_isr,
>  	.subscribe_event = adv7842_subscribe_event,
>  	.unsubscribe_event = v4l2_event_subdev_unsubscribe,
> diff --git a/drivers/media/radio/si4713/si4713.c b/drivers/media/radio/si4713/si4713.c
> index adbf43ff6a21..ae7e477774e3 100644
> --- a/drivers/media/radio/si4713/si4713.c
> +++ b/drivers/media/radio/si4713/si4713.c
> @@ -1398,6 +1398,9 @@ static const struct v4l2_ctrl_ops si4713_ctrl_ops = {
>  
>  static const struct v4l2_subdev_core_ops si4713_subdev_core_ops = {
>  	.ioctl		= si4713_ioctl,
> +#ifdef CONFIG_COMPAT
> +	.compat_ioctl32	= si4713_ioctl,
> +#endif

Should we drop v4l2_subdev_core_ops.compat_ioctl32 and call
v4l2_subdev_core_ops.ioctl from subdev_do_compat_ioctl32() ? New drivers
should design custom ioctls in a way that doesn't require compat code.

>  };
>  
>  static const struct v4l2_subdev_tuner_ops si4713_subdev_tuner_ops = {
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index bf3aa9252458..fbd176d6c415 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -686,13 +686,26 @@ static long subdev_ioctl(struct file *file, unsigned int cmd,
>  }
>  
>  #ifdef CONFIG_COMPAT
> -static long subdev_compat_ioctl32(struct file *file, unsigned int cmd,
> -	unsigned long arg)
> +static long subdev_do_compat_ioctl32(struct file *file, unsigned int cmd, void *arg)
>  {
>  	struct video_device *vdev = video_devdata(file);
>  	struct v4l2_subdev *sd = vdev_to_v4l2_subdev(vdev);
> +	struct mutex *lock = vdev->lock;
> +	long ret = -ENODEV;
>  
> -	return v4l2_subdev_call(sd, core, compat_ioctl32, cmd, arg);
> +	if (lock && mutex_lock_interruptible(lock))
> +		return -ERESTARTSYS;
> +	if (video_is_registered(vdev))
> +		ret = v4l2_subdev_call(sd, core, compat_ioctl32, cmd, arg);
> +	if (lock)
> +		mutex_unlock(lock);
> +	return ret;
> +}
> +
> +static long subdev_compat_ioctl32(struct file *file, unsigned int cmd,
> +	unsigned long arg)
> +{
> +	return video_usercopy(file, cmd, arg, subdev_do_compat_ioctl32);
>  }
>  #endif
>  
> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> index d0e9a5bdb08b..42aa1f6c7c3f 100644
> --- a/include/media/v4l2-subdev.h
> +++ b/include/media/v4l2-subdev.h
> @@ -195,8 +195,7 @@ struct v4l2_subdev_core_ops {
>  	int (*s_gpio)(struct v4l2_subdev *sd, u32 val);
>  	long (*ioctl)(struct v4l2_subdev *sd, unsigned int cmd, void *arg);
>  #ifdef CONFIG_COMPAT
> -	long (*compat_ioctl32)(struct v4l2_subdev *sd, unsigned int cmd,
> -			       unsigned long arg);
> +	long (*compat_ioctl32)(struct v4l2_subdev *sd, unsigned int cmd, void *arg);
>  #endif
>  #ifdef CONFIG_VIDEO_ADV_DEBUG
>  	int (*g_register)(struct v4l2_subdev *sd, struct v4l2_dbg_register *reg);

-- 
Regards,

Laurent Pinchart