linux-kernel - Re: [PATCH v3 7/8] media: subdev: fix compat

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Date:   Tue, 15 Jun 2021 10:26:14 +0200
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Arnd Bergmann <arnd@...nel.org>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        "Lad, Prabhakar" <prabhakar.csengg@...il.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Vaibhav Gupta <vaibhavgupta40@...il.com>,
        Liu Shixin <liushixin2@...wei.com>,
        Jacopo Mondi <jacopo+renesas@...ndi.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        linux-staging@...ts.linux.dev
Subject: Re: [PATCH v3 7/8] media: subdev: fix compat_ioctl32

On 14/06/2021 19:18, Laurent Pinchart wrote:
> Hi Arnd,
> 
> Thank you for the patch.
> 
> On Mon, Jun 14, 2021 at 12:34:08PM +0200, Arnd Bergmann wrote:
>> From: Arnd Bergmann <arnd@...db.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 The compat_ioctl32 callback for subdevs has outdated calling conventions,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@...db.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.

I agree, we can drop it completely.

I'll skip this patch, but I'll take the other 7 patches and make a v3 PR with
updated Reviewed-by tags from Laurent.

Regards,

	Hans

> 
>>  };
>>  
>>  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);
>