Hi Hans,
thanks for review
`
On Wed, Apr 01, 2020 at 01:28:08PM +0200, Hans Verkuil wrote:
> On 3/27/20 11:35 PM, Jacopo Mondi wrote:
> > Add to the V4L2 core a function to register device nodes for video
> > subdevices in read-only mode.
> >
> > Registering a device node in read-only mode is useful to expose to
> > userspace the current sub-device configuration, without allowing
> > application to change it by using the V4L2 subdevice ioctls.
> >
> > Signed-off-by: Jacopo Mondi <jacopo@xxxxxxxxxx>
> > ---
> > drivers/media/v4l2-core/v4l2-device.c | 7 +++--
> > drivers/media/v4l2-core/v4l2-subdev.c | 19 ++++++++++++
> > include/media/v4l2-dev.h | 7 +++++
> > include/media/v4l2-device.h | 42 ++++++++++++++++++++++++---
> > 4 files changed, 69 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/media/v4l2-core/v4l2-device.c b/drivers/media/v4l2-core/v4l2-device.c
> > index c69941214bb2..4517a70379ce 100644
> > --- a/drivers/media/v4l2-core/v4l2-device.c
> > +++ b/drivers/media/v4l2-core/v4l2-device.c
> > @@ -186,7 +186,8 @@ static void v4l2_device_release_subdev_node(struct video_device *vdev)
> > kfree(vdev);
> > }
> >
> > -int v4l2_device_register_subdev_nodes(struct v4l2_device *v4l2_dev)
> > +int __v4l2_device_register_subdev_nodes(struct v4l2_device *v4l2_dev,
> > + bool read_only)
> > {
> > struct video_device *vdev;
> > struct v4l2_subdev *sd;
> > @@ -215,6 +216,8 @@ int v4l2_device_register_subdev_nodes(struct v4l2_device *v4l2_dev)
> > vdev->fops = &v4l2_subdev_fops;
> > vdev->release = v4l2_device_release_subdev_node;
> > vdev->ctrl_handler = sd->ctrl_handler;
> > + if (read_only)
> > + set_bit(V4L2_FL_RO_DEVNODE, &vdev->flags);
>
> I noticed the discussion about set_bit vs BIT: if memory serves, then at some point
> in time setting/testing/clearing the V4L2_FL_REGISTERED had to be atomic. However,
> looking at it today this no longer appears to be needed, so it can probably all be
> replaced by normal bit operations. But that should be done in a separate patch if
> anyone is interested in making that change.
>
Ack, I agree it's an overkill and that it could be changed on top
> > err = __video_register_device(vdev, VFL_TYPE_SUBDEV, -1, 1,
> > sd->owner);
> > if (err < 0) {
> > @@ -252,7 +255,7 @@ int v4l2_device_register_subdev_nodes(struct v4l2_device *v4l2_dev)
> >
> > return err;
> > }
> > -EXPORT_SYMBOL_GPL(v4l2_device_register_subdev_nodes);
> > +EXPORT_SYMBOL_GPL(__v4l2_device_register_subdev_nodes);
> >
> > void v4l2_device_unregister_subdev(struct v4l2_subdev *sd)
> > {
> > diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> > index a376b351135f..87fea21919fc 100644
> > --- a/drivers/media/v4l2-core/v4l2-subdev.c
> > +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> > @@ -331,6 +331,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> > struct v4l2_fh *vfh = file->private_data;
> > #if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
> > struct v4l2_subdev_fh *subdev_fh = to_v4l2_subdev_fh(vfh);
> > + bool ro_subdev = test_bit(V4L2_FL_RO_DEVNODE, &vdev->flags);
> > #endif
> > int rval;
> >
> > @@ -477,6 +478,9 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> > case VIDIOC_SUBDEV_S_FMT: {
> > struct v4l2_subdev_format *format = arg;
> >
> > + if (format->which != V4L2_SUBDEV_FORMAT_TRY && ro_subdev)
> > + return -EPERM;
> > +
> > memset(format->reserved, 0, sizeof(format->reserved));
> > memset(format->format.reserved, 0, sizeof(format->format.reserved));
> > return v4l2_subdev_call(sd, pad, set_fmt, subdev_fh->pad, format);
> > @@ -504,6 +508,9 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> > struct v4l2_subdev_crop *crop = arg;
> > struct v4l2_subdev_selection sel;
> >
> > + if (crop->which != V4L2_SUBDEV_FORMAT_TRY && ro_subdev)
> > + return -EPERM;
> > +
> > memset(crop->reserved, 0, sizeof(crop->reserved));
> > memset(&sel, 0, sizeof(sel));
> > sel.which = crop->which;
> > @@ -545,6 +552,9 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> > case VIDIOC_SUBDEV_S_FRAME_INTERVAL: {
> > struct v4l2_subdev_frame_interval *fi = arg;
> >
> > + if (ro_subdev)
> > + return -EPERM;
> > +
> > memset(fi->reserved, 0, sizeof(fi->reserved));
> > return v4l2_subdev_call(sd, video, s_frame_interval, arg);
> > }
> > @@ -568,6 +578,9 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> > case VIDIOC_SUBDEV_S_SELECTION: {
> > struct v4l2_subdev_selection *sel = arg;
> >
> > + if (sel->which != V4L2_SUBDEV_FORMAT_TRY && ro_subdev)
> > + return -EPERM;
> > +
> > memset(sel->reserved, 0, sizeof(sel->reserved));
> > return v4l2_subdev_call(
> > sd, pad, set_selection, subdev_fh->pad, sel);
> > @@ -604,6 +617,9 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> > return v4l2_subdev_call(sd, video, g_dv_timings, arg);
> >
> > case VIDIOC_SUBDEV_S_DV_TIMINGS:
> > + if (ro_subdev)
> > + return -EPERM;
> > +
> > return v4l2_subdev_call(sd, video, s_dv_timings, arg);
> >
> > case VIDIOC_SUBDEV_G_STD:
> > @@ -612,6 +628,9 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> > case VIDIOC_SUBDEV_S_STD: {
> > v4l2_std_id *std = arg;
> >
> > + if (ro_subdev)
> > + return -EPERM;
> > +
> > return v4l2_subdev_call(sd, video, s_std, *std);
> > }
> >
> > diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
> > index 4602c15ff878..bdbd953a976c 100644
> > --- a/include/media/v4l2-dev.h
> > +++ b/include/media/v4l2-dev.h
> > @@ -82,11 +82,18 @@ struct v4l2_ctrl_handler;
> > * but the old crop API will still work as expected in order to preserve
> > * backwards compatibility.
> > * Never set this flag for new drivers.
> > + * @V4L2_FL_RO_DEVNODE:
> > + * indicates that the video device node is registered in read-only mode.
> > + * The flag only applies to device nodes registered for sub-devices, it is
> > + * set by the core when the sub-devices device nodes are registered with
> > + * v4l2_device_register_ro_subdev_nodes() and used by the sub-device ioctl
> > + * handler to restrict access to some ioctl calls.
> > */
> > enum v4l2_video_device_flags {
> > V4L2_FL_REGISTERED = 0,
> > V4L2_FL_USES_V4L2_FH = 1,
> > V4L2_FL_QUIRK_INVERTED_CROP = 2,
> > + V4L2_FL_RO_DEVNODE = 3,
>
> I think this should be renamed to V4L2_FL_SUBDEV_RO_DEVNODE since this is subdev
> specific and not for general device node usage. 'SUBDEV' should definitely be
> part of the flag name.
>
True indeed! I'll rename the flag
Thanks
j
> > };
> >
> > /* Priority helper functions */
> > diff --git a/include/media/v4l2-device.h b/include/media/v4l2-device.h
> > index 7c912b7d2870..c01aa9df70b5 100644
> > --- a/include/media/v4l2-device.h
> > +++ b/include/media/v4l2-device.h
> > @@ -174,14 +174,48 @@ int __must_check v4l2_device_register_subdev(struct v4l2_device *v4l2_dev,
> > void v4l2_device_unregister_subdev(struct v4l2_subdev *sd);
> >
> > /**
> > - * v4l2_device_register_subdev_nodes - Registers device nodes for all subdevs
> > - * of the v4l2 device that are marked with
> > - * the %V4L2_SUBDEV_FL_HAS_DEVNODE flag.
> > + * __v4l2_device_register_ro_subdev_nodes - Registers device nodes for
> > + * all subdevs of the v4l2 device that are marked with the
> > + * %V4L2_SUBDEV_FL_HAS_DEVNODE flag.
> > *
> > * @v4l2_dev: pointer to struct v4l2_device
> > + * @read_only: subdevices read-only flag. True to register the subdevices
> > + * device nodes in read-only mode, false to allow full access to the
> > + * subdevice userspace API.
> > */
> > int __must_check
> > -v4l2_device_register_subdev_nodes(struct v4l2_device *v4l2_dev);
> > +__v4l2_device_register_subdev_nodes(struct v4l2_device *v4l2_dev,
> > + bool read_only);
> > +
> > +/**
> > + * v4l2_device_register_subdev_nodes - Registers subdevices device nodes with
> > + * unrestricted access to the subdevice userspace operations
> > + *
> > + * Internally calls __v4l2_device_register_subdev_nodes(). See its documentation
> > + * for more details.
> > + *
> > + * @v4l2_dev: pointer to struct v4l2_device
> > + */
> > +static inline int __must_check
> > +v4l2_device_register_subdev_nodes(struct v4l2_device *v4l2_dev)
> > +{
> > + return __v4l2_device_register_subdev_nodes(v4l2_dev, false);
> > +}
> > +
> > +/**
> > + * v4l2_device_register_ro_subdev_nodes - Registers subdevices device nodes
> > + * in read-only mode
> > + *
> > + * Internally calls __v4l2_device_register_subdev_nodes(). See its documentation
> > + * for more details.
> > + *
> > + * @v4l2_dev: pointer to struct v4l2_device
> > + */
> > +static inline int __must_check
> > +v4l2_device_register_ro_subdev_nodes(struct v4l2_device *v4l2_dev)
> > +{
> > + return __v4l2_device_register_subdev_nodes(v4l2_dev, true);
> > +}
> >
> > /**
> > * v4l2_subdev_notify - Sends a notification to v4l2_device.
> > --
> > 2.25.1
> >
>
> Regards,
>
> Hans
