Re: [RFCv1 PATCH 5/5] v4l2-dev: add flag to have the core lock all file operations.

[Hans de Goede <hdegoede@redhat.com>]

Hi,

Looks good, ack.

Acked-by: Hans de Goede <hdegoede@redhat.com>

Regards,

Hans


On 05/10/2012 09:05 AM, Hans Verkuil wrote:
> From: Hans Verkuil<hans.verkuil@cisco.com>
>
> This used to be the default if the lock pointer was set, but now that lock is by
> default only used for ioctl serialization. Those drivers that already used
> core locking have this flag set explicitly, except for some drivers where
> it was obvious that there was no need to serialize any file operations other
> than ioctl.
>
> The drivers that didn't need this flag were:
>
> drivers/media/radio/dsbr100.c
> drivers/media/radio/radio-isa.c
> drivers/media/radio/radio-keene.c
> drivers/media/radio/radio-miropcm20.c
> drivers/media/radio/radio-mr800.c
> drivers/media/radio/radio-tea5764.c
> drivers/media/radio/radio-timb.c
> drivers/media/video/vivi.c
> sound/i2c/other/tea575x-tuner.c
>
> The other drivers that use core locking and where it was not immediately
> obvious that this flag wasn't needed were changed so that the flag is set
> together with a comment that that driver needs work to avoid having to
> set that flag. This will often involve taking the core lock in the fops
> themselves.
>
> Eventually this flag should go and it should not be used in new drivers.
>
> There are a few reasons why we want to avoid core locking of non-ioctl
> fops: in the case of mmap this can lead to a deadlock in rare situations
> since when mmap is called the mmap_sem is held and it is possible for
> other parts of the code to take that lock as well (copy_from_user()/copy_to_user()
> perform a down_read(&mm->mmap_sem) when a page fault occurs).
>
> It is very unlikely that that happens since the core lock serializes all
> fops, but the kernel warns about it if lock validation is turned on.
>
> For poll it is also undesirable to take the core lock as that can introduce
> increased latency. The same is true for read/write.
>
> While it was possible to make flags or something to turn on/off taking the
> core lock for each file operation, in practice it is much simpler to just
> not take it at all except for ioctl and leave it to the driver to take the
> lock. There are only a handful fops compared to the zillion ioctls we have.
>
> I also wanted to make it obvious which drivers still take the lock for all
> fops, so that's why I chose to have drivers set it explicitly.
>
> Signed-off-by: Hans Verkuil<hans.verkuil@cisco.com>
> ---
>   drivers/media/common/saa7146_fops.c             |    4 +++
>   drivers/media/radio/wl128x/fmdrv_v4l2.c         |    4 +++
>   drivers/media/video/blackfin/bfin_capture.c     |    4 +++
>   drivers/media/video/cpia2/cpia2_v4l.c           |    4 +++
>   drivers/media/video/cx231xx/cx231xx-video.c     |    4 +++
>   drivers/media/video/davinci/vpbe_display.c      |    4 +++
>   drivers/media/video/davinci/vpif_capture.c      |    4 +++
>   drivers/media/video/davinci/vpif_display.c      |    4 +++
>   drivers/media/video/em28xx/em28xx-video.c       |    4 +++
>   drivers/media/video/fsl-viu.c                   |    4 +++
>   drivers/media/video/ivtv/ivtv-streams.c         |    4 +++
>   drivers/media/video/mem2mem_testdev.c           |    4 +++
>   drivers/media/video/mx2_emmaprp.c               |    4 +++
>   drivers/media/video/s2255drv.c                  |    4 +++
>   drivers/media/video/s5p-fimc/fimc-capture.c     |    4 +++
>   drivers/media/video/s5p-fimc/fimc-core.c        |    4 +++
>   drivers/media/video/s5p-g2d/g2d.c               |    4 +++
>   drivers/media/video/s5p-jpeg/jpeg-core.c        |    8 ++++++
>   drivers/media/video/s5p-mfc/s5p_mfc.c           |    6 +++++
>   drivers/media/video/s5p-tv/mixer_video.c        |    4 +++
>   drivers/media/video/sh_vou.c                    |    4 +++
>   drivers/media/video/soc_camera.c                |    4 +++
>   drivers/media/video/tm6000/tm6000-video.c       |    4 +++
>   drivers/media/video/usbvision/usbvision-video.c |    4 +++
>   drivers/media/video/v4l2-dev.c                  |   32 ++++++++++++++---------
>   drivers/staging/media/dt3155v4l/dt3155v4l.c     |    4 +++
>   include/media/v4l2-dev.h                        |    3 +++
>   27 files changed, 129 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/media/common/saa7146_fops.c b/drivers/media/common/saa7146_fops.c
> index 71f8e01..8d7df1a 100644
> --- a/drivers/media/common/saa7146_fops.c
> +++ b/drivers/media/common/saa7146_fops.c
> @@ -511,6 +511,10 @@ int saa7146_register_device(struct video_device **vid, struct saa7146_dev* dev,
>   	vfd->fops =&video_fops;
>   	vfd->ioctl_ops =&dev->ext_vv_data->ops;
>   	vfd->release = video_device_release;
> +	/* Locking in file operations other than ioctl should be done by
> +	   the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&vfd->flags);
>   	vfd->lock =&dev->v4l2_lock;
>   	vfd->tvnorms = 0;
>   	for (i = 0; i<  dev->ext_vv_data->num_stds; i++)
> diff --git a/drivers/media/radio/wl128x/fmdrv_v4l2.c b/drivers/media/radio/wl128x/fmdrv_v4l2.c
> index 077d369..080b96a 100644
> --- a/drivers/media/radio/wl128x/fmdrv_v4l2.c
> +++ b/drivers/media/radio/wl128x/fmdrv_v4l2.c
> @@ -518,6 +518,10 @@ int fm_v4l2_init_video_device(struct fmdev *fmdev, int radio_nr)
>   	video_set_drvdata(gradio_dev, fmdev);
>
>   	gradio_dev->lock =&fmdev->mutex;
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&gradio_dev->flags);
>
>   	/* Register with V4L2 subsystem as RADIO device */
>   	if (video_register_device(gradio_dev, VFL_TYPE_RADIO, radio_nr)) {
> diff --git a/drivers/media/video/blackfin/bfin_capture.c b/drivers/media/video/blackfin/bfin_capture.c
> index 514fcf7..0aba45e 100644
> --- a/drivers/media/video/blackfin/bfin_capture.c
> +++ b/drivers/media/video/blackfin/bfin_capture.c
> @@ -942,6 +942,10 @@ static int __devinit bcap_probe(struct platform_device *pdev)
>   	INIT_LIST_HEAD(&bcap_dev->dma_queue);
>
>   	vfd->lock =&bcap_dev->mutex;
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&vfd->flags);
>
>   	/* register video device */
>   	ret = video_register_device(bcap_dev->video_dev, VFL_TYPE_GRABBER, -1);
> diff --git a/drivers/media/video/cpia2/cpia2_v4l.c b/drivers/media/video/cpia2/cpia2_v4l.c
> index bb4f1d0..55e9290 100644
> --- a/drivers/media/video/cpia2/cpia2_v4l.c
> +++ b/drivers/media/video/cpia2/cpia2_v4l.c
> @@ -1147,6 +1147,10 @@ int cpia2_register_camera(struct camera_data *cam)
>   	cam->vdev.ctrl_handler = hdl;
>   	cam->vdev.v4l2_dev =&cam->v4l2_dev;
>   	set_bit(V4L2_FL_USE_FH_PRIO,&cam->vdev.flags);
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&cam->vdev.flags);
>
>   	reset_camera_struct_v4l(cam);
>
> diff --git a/drivers/media/video/cx231xx/cx231xx-video.c b/drivers/media/video/cx231xx/cx231xx-video.c
> index 7f916f0..2a04558 100644
> --- a/drivers/media/video/cx231xx/cx231xx-video.c
> +++ b/drivers/media/video/cx231xx/cx231xx-video.c
> @@ -2561,6 +2561,10 @@ static struct video_device *cx231xx_vdev_init(struct cx231xx *dev,
>   	vfd->release = video_device_release;
>   	vfd->debug = video_debug;
>   	vfd->lock =&dev->lock;
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&vfd->flags);
>
>   	snprintf(vfd->name, sizeof(vfd->name), "%s %s", dev->name, type_name);
>
> diff --git a/drivers/media/video/davinci/vpbe_display.c b/drivers/media/video/davinci/vpbe_display.c
> index 1f3b1c7..e106b72 100644
> --- a/drivers/media/video/davinci/vpbe_display.c
> +++ b/drivers/media/video/davinci/vpbe_display.c
> @@ -1618,6 +1618,10 @@ static __devinit int init_vpbe_layer(int i, struct vpbe_display *disp_dev,
>   	vbd->ioctl_ops	=&vpbe_ioctl_ops;
>   	vbd->minor	= -1;
>   	vbd->v4l2_dev   =&disp_dev->vpbe_dev->v4l2_dev;
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&vbd->flags);
>   	vbd->lock	=&vpbe_display_layer->opslock;
>
>   	if (disp_dev->vpbe_dev->current_timings.timings_type&
> diff --git a/drivers/media/video/davinci/vpif_capture.c b/drivers/media/video/davinci/vpif_capture.c
> index 6504e40..9604695 100644
> --- a/drivers/media/video/davinci/vpif_capture.c
> +++ b/drivers/media/video/davinci/vpif_capture.c
> @@ -2228,6 +2228,10 @@ static __init int vpif_probe(struct platform_device *pdev)
>   		common =&(ch->common[VPIF_VIDEO_INDEX]);
>   		spin_lock_init(&common->irqlock);
>   		mutex_init(&common->lock);
> +		/* Locking in file operations other than ioctl should be done
> +		   by the driver, not the V4L2 core.
> +		   This driver needs auditing so that this flag can be removed. */
> +		set_bit(V4L2_FL_LOCK_ALL_FOPS,&ch->video_dev->flags);
>   		ch->video_dev->lock =&common->lock;
>   		/* Initialize prio member of channel object */
>   		v4l2_prio_init(&ch->prio);
> diff --git a/drivers/media/video/davinci/vpif_display.c b/drivers/media/video/davinci/vpif_display.c
> index 7fa34b4..e6488ee 100644
> --- a/drivers/media/video/davinci/vpif_display.c
> +++ b/drivers/media/video/davinci/vpif_display.c
> @@ -1778,6 +1778,10 @@ static __init int vpif_probe(struct platform_device *pdev)
>   		v4l2_prio_init(&ch->prio);
>   		ch->common[VPIF_VIDEO_INDEX].fmt.type =
>   						V4L2_BUF_TYPE_VIDEO_OUTPUT;
> +		/* Locking in file operations other than ioctl should be done
> +		   by the driver, not the V4L2 core.
> +		   This driver needs auditing so that this flag can be removed. */
> +		set_bit(V4L2_FL_LOCK_ALL_FOPS,&ch->video_dev->flags);
>   		ch->video_dev->lock =&common->lock;
>
>   		/* register video device */
> diff --git a/drivers/media/video/em28xx/em28xx-video.c b/drivers/media/video/em28xx/em28xx-video.c
> index bcc4160..308a1dd 100644
> --- a/drivers/media/video/em28xx/em28xx-video.c
> +++ b/drivers/media/video/em28xx/em28xx-video.c
> @@ -2495,6 +2495,10 @@ static struct video_device *em28xx_vdev_init(struct em28xx *dev,
>   	vfd->release	= video_device_release;
>   	vfd->debug	= video_debug;
>   	vfd->lock	=&dev->lock;
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&vfd->flags);
>
>   	snprintf(vfd->name, sizeof(vfd->name), "%s %s",
>   		 dev->name, type_name);
> diff --git a/drivers/media/video/fsl-viu.c b/drivers/media/video/fsl-viu.c
> index 27e3e0c..777486f 100644
> --- a/drivers/media/video/fsl-viu.c
> +++ b/drivers/media/video/fsl-viu.c
> @@ -1544,6 +1544,10 @@ static int __devinit viu_of_probe(struct platform_device *op)
>
>   	/* initialize locks */
>   	mutex_init(&viu_dev->lock);
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&viu_dev->vdev->flags);
>   	viu_dev->vdev->lock =&viu_dev->lock;
>   	spin_lock_init(&viu_dev->slock);
>
> diff --git a/drivers/media/video/ivtv/ivtv-streams.c b/drivers/media/video/ivtv/ivtv-streams.c
> index 7ea5ca7..6738592 100644
> --- a/drivers/media/video/ivtv/ivtv-streams.c
> +++ b/drivers/media/video/ivtv/ivtv-streams.c
> @@ -228,6 +228,10 @@ static int ivtv_prep_dev(struct ivtv *itv, int type)
>   	s->vdev->release = video_device_release;
>   	s->vdev->tvnorms = V4L2_STD_ALL;
>   	s->vdev->lock =&itv->serialize_lock;
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&s->vdev->flags);
>   	set_bit(V4L2_FL_USE_FH_PRIO,&s->vdev->flags);
>   	ivtv_set_funcs(s->vdev);
>   	return 0;
> diff --git a/drivers/media/video/mem2mem_testdev.c b/drivers/media/video/mem2mem_testdev.c
> index 12897e8..ee3efbd 100644
> --- a/drivers/media/video/mem2mem_testdev.c
> +++ b/drivers/media/video/mem2mem_testdev.c
> @@ -958,6 +958,10 @@ static int m2mtest_probe(struct platform_device *pdev)
>   	}
>
>   	*vfd = m2mtest_videodev;
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&vfd->flags);
>   	vfd->lock =&dev->dev_mutex;
>
>   	ret = video_register_device(vfd, VFL_TYPE_GRABBER, 0);
> diff --git a/drivers/media/video/mx2_emmaprp.c b/drivers/media/video/mx2_emmaprp.c
> index 55ac173..0bd5815 100644
> --- a/drivers/media/video/mx2_emmaprp.c
> +++ b/drivers/media/video/mx2_emmaprp.c
> @@ -904,6 +904,10 @@ static int emmaprp_probe(struct platform_device *pdev)
>   	}
>
>   	*vfd = emmaprp_videodev;
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&vfd->flags);
>   	vfd->lock =&pcdev->dev_mutex;
>
>   	video_set_drvdata(vfd, pcdev);
> diff --git a/drivers/media/video/s2255drv.c b/drivers/media/video/s2255drv.c
> index 37845de..ea974fa 100644
> --- a/drivers/media/video/s2255drv.c
> +++ b/drivers/media/video/s2255drv.c
> @@ -1948,6 +1948,10 @@ static int s2255_probe_v4l(struct s2255_dev *dev)
>   		/* register 4 video devices */
>   		channel->vdev = template;
>   		channel->vdev.lock =&dev->lock;
> +		/* Locking in file operations other than ioctl should be done
> +		   by the driver, not the V4L2 core.
> +		   This driver needs auditing so that this flag can be removed. */
> +		set_bit(V4L2_FL_LOCK_ALL_FOPS,&channel->vdev.flags);
>   		channel->vdev.v4l2_dev =&dev->v4l2_dev;
>   		video_set_drvdata(&channel->vdev, channel);
>   		if (video_nr == -1)
> diff --git a/drivers/media/video/s5p-fimc/fimc-capture.c b/drivers/media/video/s5p-fimc/fimc-capture.c
> index dc18ba5..72d5150 100644
> --- a/drivers/media/video/s5p-fimc/fimc-capture.c
> +++ b/drivers/media/video/s5p-fimc/fimc-capture.c
> @@ -1516,6 +1516,10 @@ int fimc_register_capture_device(struct fimc_dev *fimc,
>   	vfd->minor	= -1;
>   	vfd->release	= video_device_release;
>   	vfd->lock	=&fimc->lock;
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&vfd->flags);
>   	video_set_drvdata(vfd, fimc);
>
>   	vid_cap =&fimc->vid_cap;
> diff --git a/drivers/media/video/s5p-fimc/fimc-core.c b/drivers/media/video/s5p-fimc/fimc-core.c
> index 7b90a89..c58dd9f 100644
> --- a/drivers/media/video/s5p-fimc/fimc-core.c
> +++ b/drivers/media/video/s5p-fimc/fimc-core.c
> @@ -1520,6 +1520,10 @@ int fimc_register_m2m_device(struct fimc_dev *fimc,
>   	vfd->minor	= -1;
>   	vfd->release	= video_device_release;
>   	vfd->lock	=&fimc->lock;
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&vfd->flags);
>
>   	snprintf(vfd->name, sizeof(vfd->name), "%s.m2m", dev_name(&pdev->dev));
>   	video_set_drvdata(vfd, fimc);
> diff --git a/drivers/media/video/s5p-g2d/g2d.c b/drivers/media/video/s5p-g2d/g2d.c
> index 789de74..02605ce 100644
> --- a/drivers/media/video/s5p-g2d/g2d.c
> +++ b/drivers/media/video/s5p-g2d/g2d.c
> @@ -762,6 +762,10 @@ static int g2d_probe(struct platform_device *pdev)
>   		goto unreg_v4l2_dev;
>   	}
>   	*vfd = g2d_videodev;
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&vfd->flags);
>   	vfd->lock =&dev->mutex;
>   	ret = video_register_device(vfd, VFL_TYPE_GRABBER, 0);
>   	if (ret) {
> diff --git a/drivers/media/video/s5p-jpeg/jpeg-core.c b/drivers/media/video/s5p-jpeg/jpeg-core.c
> index 5a49c30..ecf7b0b 100644
> --- a/drivers/media/video/s5p-jpeg/jpeg-core.c
> +++ b/drivers/media/video/s5p-jpeg/jpeg-core.c
> @@ -1386,6 +1386,10 @@ static int s5p_jpeg_probe(struct platform_device *pdev)
>   	jpeg->vfd_encoder->release	= video_device_release;
>   	jpeg->vfd_encoder->lock		=&jpeg->lock;
>   	jpeg->vfd_encoder->v4l2_dev	=&jpeg->v4l2_dev;
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&jpeg->vfd_encoder->flags);
>
>   	ret = video_register_device(jpeg->vfd_encoder, VFL_TYPE_GRABBER, -1);
>   	if (ret) {
> @@ -1413,6 +1417,10 @@ static int s5p_jpeg_probe(struct platform_device *pdev)
>   	jpeg->vfd_decoder->release	= video_device_release;
>   	jpeg->vfd_decoder->lock		=&jpeg->lock;
>   	jpeg->vfd_decoder->v4l2_dev	=&jpeg->v4l2_dev;
> +	/* Locking in file operations other than ioctl should be done by the driver,
> +	   not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&jpeg->vfd_decoder->flags);
>
>   	ret = video_register_device(jpeg->vfd_decoder, VFL_TYPE_GRABBER, -1);
>   	if (ret) {
> diff --git a/drivers/media/video/s5p-mfc/s5p_mfc.c b/drivers/media/video/s5p-mfc/s5p_mfc.c
> index 83fe461..7600854 100644
> --- a/drivers/media/video/s5p-mfc/s5p_mfc.c
> +++ b/drivers/media/video/s5p-mfc/s5p_mfc.c
> @@ -1048,6 +1048,10 @@ static int s5p_mfc_probe(struct platform_device *pdev)
>   	vfd->ioctl_ops	= get_dec_v4l2_ioctl_ops();
>   	vfd->release	= video_device_release,
>   	vfd->lock	=&dev->mfc_mutex;
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&vfd->flags);
>   	vfd->v4l2_dev	=&dev->v4l2_dev;
>   	snprintf(vfd->name, sizeof(vfd->name), "%s", S5P_MFC_DEC_NAME);
>   	dev->vfd_dec	= vfd;
> @@ -1072,6 +1076,8 @@ static int s5p_mfc_probe(struct platform_device *pdev)
>   	vfd->ioctl_ops	= get_enc_v4l2_ioctl_ops();
>   	vfd->release	= video_device_release,
>   	vfd->lock	=&dev->mfc_mutex;
> +	/* This should not be necessary */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&vfd->flags);
>   	vfd->v4l2_dev	=&dev->v4l2_dev;
>   	snprintf(vfd->name, sizeof(vfd->name), "%s", S5P_MFC_ENC_NAME);
>   	dev->vfd_enc	= vfd;
> diff --git a/drivers/media/video/s5p-tv/mixer_video.c b/drivers/media/video/s5p-tv/mixer_video.c
> index f7ca5cc..c0eadd7 100644
> --- a/drivers/media/video/s5p-tv/mixer_video.c
> +++ b/drivers/media/video/s5p-tv/mixer_video.c
> @@ -1069,6 +1069,10 @@ struct mxr_layer *mxr_base_layer_create(struct mxr_device *mdev,
>   	set_bit(V4L2_FL_USE_FH_PRIO,&layer->vfd.flags);
>
>   	video_set_drvdata(&layer->vfd, layer);
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&layer->vfd.flags);
>   	layer->vfd.lock =&layer->mutex;
>   	layer->vfd.v4l2_dev =&mdev->v4l2_dev;
>
> diff --git a/drivers/media/video/sh_vou.c b/drivers/media/video/sh_vou.c
> index 9644bd8..8fd1874 100644
> --- a/drivers/media/video/sh_vou.c
> +++ b/drivers/media/video/sh_vou.c
> @@ -1390,6 +1390,10 @@ static int __devinit sh_vou_probe(struct platform_device *pdev)
>   	vdev->v4l2_dev =&vou_dev->v4l2_dev;
>   	vdev->release = video_device_release;
>   	vdev->lock =&vou_dev->fop_lock;
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&vdev->flags);
>
>   	vou_dev->vdev = vdev;
>   	video_set_drvdata(vdev, vou_dev);
> diff --git a/drivers/media/video/soc_camera.c b/drivers/media/video/soc_camera.c
> index eb25756..c27bb6d 100644
> --- a/drivers/media/video/soc_camera.c
> +++ b/drivers/media/video/soc_camera.c
> @@ -1425,6 +1425,10 @@ static int video_dev_create(struct soc_camera_device *icd)
>   	vdev->tvnorms		= V4L2_STD_UNKNOWN;
>   	vdev->ctrl_handler	=&icd->ctrl_handler;
>   	vdev->lock		=&icd->video_lock;
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&vdev->flags);
>
>   	icd->vdev = vdev;
>
> diff --git a/drivers/media/video/tm6000/tm6000-video.c b/drivers/media/video/tm6000/tm6000-video.c
> index 1ba26d5..375f26a 100644
> --- a/drivers/media/video/tm6000/tm6000-video.c
> +++ b/drivers/media/video/tm6000/tm6000-video.c
> @@ -1731,6 +1731,10 @@ static struct video_device *vdev_init(struct tm6000_core *dev,
>   	vfd->release = video_device_release;
>   	vfd->debug = tm6000_debug;
>   	vfd->lock =&dev->lock;
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&vfd->flags);
>
>   	snprintf(vfd->name, sizeof(vfd->name), "%s %s", dev->name, type_name);
>
> diff --git a/drivers/media/video/usbvision/usbvision-video.c b/drivers/media/video/usbvision/usbvision-video.c
> index 5a74f5e..9bd8f08 100644
> --- a/drivers/media/video/usbvision/usbvision-video.c
> +++ b/drivers/media/video/usbvision/usbvision-video.c
> @@ -1296,6 +1296,10 @@ static struct video_device *usbvision_vdev_init(struct usb_usbvision *usbvision,
>   	if (NULL == vdev)
>   		return NULL;
>   	*vdev = *vdev_template;
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&vdev->flags);
>   	vdev->lock =&usbvision->v4l2_lock;
>   	vdev->v4l2_dev =&usbvision->v4l2_dev;
>   	snprintf(vdev->name, sizeof(vdev->name), "%s", name);
> diff --git a/drivers/media/video/v4l2-dev.c b/drivers/media/video/v4l2-dev.c
> index 4d98ee1..5b819c9 100644
> --- a/drivers/media/video/v4l2-dev.c
> +++ b/drivers/media/video/v4l2-dev.c
> @@ -274,11 +274,12 @@ static ssize_t v4l2_read(struct file *filp, char __user *buf,
>
>   	if (!vdev->fops->read)
>   		return -EINVAL;
> -	if (vdev->lock&&  mutex_lock_interruptible(vdev->lock))
> +	if (test_bit(V4L2_FL_LOCK_ALL_FOPS,&vdev->flags)&&
> +	    mutex_lock_interruptible(vdev->lock))
>   		return -ERESTARTSYS;
>   	if (video_is_registered(vdev))
>   		ret = vdev->fops->read(filp, buf, sz, off);
> -	if (vdev->lock)
> +	if (test_bit(V4L2_FL_LOCK_ALL_FOPS,&vdev->flags))
>   		mutex_unlock(vdev->lock);
>   	return ret;
>   }
> @@ -291,11 +292,12 @@ static ssize_t v4l2_write(struct file *filp, const char __user *buf,
>
>   	if (!vdev->fops->write)
>   		return -EINVAL;
> -	if (vdev->lock&&  mutex_lock_interruptible(vdev->lock))
> +	if (test_bit(V4L2_FL_LOCK_ALL_FOPS,&vdev->flags)&&
> +	    mutex_lock_interruptible(vdev->lock))
>   		return -ERESTARTSYS;
>   	if (video_is_registered(vdev))
>   		ret = vdev->fops->write(filp, buf, sz, off);
> -	if (vdev->lock)
> +	if (test_bit(V4L2_FL_LOCK_ALL_FOPS,&vdev->flags))
>   		mutex_unlock(vdev->lock);
>   	return ret;
>   }
> @@ -307,11 +309,11 @@ static unsigned int v4l2_poll(struct file *filp, struct poll_table_struct *poll)
>
>   	if (!vdev->fops->poll)
>   		return DEFAULT_POLLMASK;
> -	if (vdev->lock)
> +	if (test_bit(V4L2_FL_LOCK_ALL_FOPS,&vdev->flags))
>   		mutex_lock(vdev->lock);
>   	if (video_is_registered(vdev))
>   		ret = vdev->fops->poll(filp, poll);
> -	if (vdev->lock)
> +	if (test_bit(V4L2_FL_LOCK_ALL_FOPS,&vdev->flags))
>   		mutex_unlock(vdev->lock);
>   	return ret;
>   }
> @@ -399,11 +401,12 @@ static int v4l2_mmap(struct file *filp, struct vm_area_struct *vm)
>
>   	if (!vdev->fops->mmap)
>   		return ret;
> -	if (vdev->lock&&  mutex_lock_interruptible(vdev->lock))
> +	if (test_bit(V4L2_FL_LOCK_ALL_FOPS,&vdev->flags)&&
> +	    mutex_lock_interruptible(vdev->lock))
>   		return -ERESTARTSYS;
>   	if (video_is_registered(vdev))
>   		ret = vdev->fops->mmap(filp, vm);
> -	if (vdev->lock)
> +	if (test_bit(V4L2_FL_LOCK_ALL_FOPS,&vdev->flags))
>   		mutex_unlock(vdev->lock);
>   	return ret;
>   }
> @@ -426,7 +429,8 @@ static int v4l2_open(struct inode *inode, struct file *filp)
>   	video_get(vdev);
>   	mutex_unlock(&videodev_lock);
>   	if (vdev->fops->open) {
> -		if (vdev->lock&&  mutex_lock_interruptible(vdev->lock)) {
> +		if (test_bit(V4L2_FL_LOCK_ALL_FOPS,&vdev->flags)&&
> +		    mutex_lock_interruptible(vdev->lock)) {
>   			ret = -ERESTARTSYS;
>   			goto err;
>   		}
> @@ -434,7 +438,7 @@ static int v4l2_open(struct inode *inode, struct file *filp)
>   			ret = vdev->fops->open(filp);
>   		else
>   			ret = -ENODEV;
> -		if (vdev->lock)
> +		if (test_bit(V4L2_FL_LOCK_ALL_FOPS,&vdev->flags))
>   			mutex_unlock(vdev->lock);
>   	}
>
> @@ -452,10 +456,10 @@ static int v4l2_release(struct inode *inode, struct file *filp)
>   	int ret = 0;
>
>   	if (vdev->fops->release) {
> -		if (vdev->lock)
> +		if (test_bit(V4L2_FL_LOCK_ALL_FOPS,&vdev->flags))
>   			mutex_lock(vdev->lock);
>   		vdev->fops->release(filp);
> -		if (vdev->lock)
> +		if (test_bit(V4L2_FL_LOCK_ALL_FOPS,&vdev->flags))
>   			mutex_unlock(vdev->lock);
>   	}
>   	/* decrease the refcount unconditionally since the release()
> @@ -831,6 +835,10 @@ int __video_register_device(struct video_device *vdev, int type, int nr,
>   	WARN_ON(video_device[vdev->minor] != NULL);
>   	vdev->index = get_index(vdev);
>   	mutex_unlock(&videodev_lock);
> +	/* if no lock was passed, then make sure the LOCK_ALL_FOPS bit is
> +	   clear and warn if it wasn't. */
> +	if (vdev->lock == NULL)
> +		WARN_ON(test_and_clear_bit(V4L2_FL_LOCK_ALL_FOPS,&vdev->flags));
>
>   	determine_valid_ioctls(vdev);
>
> diff --git a/drivers/staging/media/dt3155v4l/dt3155v4l.c b/drivers/staging/media/dt3155v4l/dt3155v4l.c
> index 280c84e..c365cdf 100644
> --- a/drivers/staging/media/dt3155v4l/dt3155v4l.c
> +++ b/drivers/staging/media/dt3155v4l/dt3155v4l.c
> @@ -898,6 +898,10 @@ dt3155_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>   	INIT_LIST_HEAD(&pd->dmaq);
>   	mutex_init(&pd->mux);
>   	pd->vdev->lock =&pd->mux; /* for locking v4l2_file_operations */
> +	/* Locking in file operations other than ioctl should be done
> +	   by the driver, not the V4L2 core.
> +	   This driver needs auditing so that this flag can be removed. */
> +	set_bit(V4L2_FL_LOCK_ALL_FOPS,&pd->vdev->flags);
>   	spin_lock_init(&pd->lock);
>   	pd->csr2 = csr2_init;
>   	pd->config = config_init;
> diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
> index 15e2fe4..9eb970b 100644
> --- a/include/media/v4l2-dev.h
> +++ b/include/media/v4l2-dev.h
> @@ -39,6 +39,9 @@ struct v4l2_ctrl_handler;
>   #define V4L2_FL_USES_V4L2_FH	(1)
>   /* Use the prio field of v4l2_fh for core priority checking */
>   #define V4L2_FL_USE_FH_PRIO	(2)
> +/* If ioctl core locking is in use, then apply that also to all
> +   file operations. */
> +#define V4L2_FL_LOCK_ALL_FOPS	(3)
>
>   /* Priority helper functions */
>