[PATCH v5 0/6] media: Register read-only sub-dev devnode

[PATCH v5 0/6] media: Register read-only sub-dev devnode

[Jacopo Mondi]

v5 addresses a few comments from Sakari and Laurent on documentation and
introduces "media: v4l2-subdev: Assume V4L2_SUBDEV_API is selected"
which removes checks for CONFIG_V4L2_SUBDEV_API from v4l2-subdev.c as
the subdevice device node is only registered if that option was selected in
first place.

Copy of v4 and v3 cover letter is below reported

-------------------------------------------------------------------------------
v4 is now rebased on top of latest media master which has moved documentation
around quite a bit.

v4 includes two patches originally from Hans to add support for SUBDEV_QUERYCAP
ioctl. Compared to its initial version only capabilities flags and version are
reported.
https://git.linuxtv.org/hverkuil/media_tree.git/log/?h=subdev-querycap

I chose to report both the RO and RW capabilities flag to make it possible for
userspace to test on both cases, as RW was the 'standard' so far, the flag could
be removed if considered not necessary.

Checkpatch reports:
WARNING: LINUX_VERSION_CODE should be avoided, code should be for the version to which it is merged
#44: FILE: drivers/media/v4l2-core/v4l2-subdev.c:344:
+		cap->version = LINUX_VERSION_CODE;

but I see LINUX_VERSION_CODE being used to version the media controller as well,
so I assume it's a false positive.

-------------------------------------------------------------------------------
Add new function v4l2_device_register_ro_subdev_nodes() to pair with
v4l2_device_register_subdev_nodes() that allows a bridge driver to register the
device node for its subdevices in read-only mode.

Devnode-centric (aka non-MC) bridge drivers control their subdevices through
direct calls to v4l2 subdev operations and do not want userspace to be able
to control the subdevice configuration by calling ioctls on the sub-device
devnode. For this reason, they usually refrain from registering any devnode at
all for their subdevices.

However it is sometimes required for userspace to access the sub-dev device
nodes to collect information on the actual configuration, without changing
the one currently applied to the device.

This requirement became pressing while working on libcamera on devnode-centric
platforms that do not expose any sub-device for their camera sensor to prevent
userspace from changing their configuration. To allow them to register device
node and being guaranteed to retain control of the subdevice configuration this
series proposes a way to register device nodes in read-only to restrict
access to all ioctls that could potentially affect the sub-dev configuration.
-------------------------------------------------------------------------------

Thanks
   j

v4->v5:
- Add "media: v4l2-subdev: Assume V4L2_SUBDEV_API is selected"
- Use BIT() instead of manual bitshifting
- Use tabs in documentation in place of 8 spaces
- minor documentation fixes

v3->v4:
- Rebase v3 on latest media master and new documentation layout
- Add SUBDEV_QUERYCAP support

v2->v3:
- Add Sakari's ack to the series
- Documentation:
  - Address Sakari' and Hans suggestions
- Implementation:
  - Rename V4L2_FL_RO_DEVNODE to V4L2_FL_SUBDEV_RO_DEVNODE
  - Limit the ability to register sub-device video device nodes to
    driver claiming support for CONFIG_VIDEO_V4L2_SUBDEV_API

v1->v2:
- Documentation:
  - Add a new patch using Laurent's suggestion to update the sub-device
    userspace API introduction
  - Take in some of Laurent's suggestions in v4l2-subdev.rst and add a new
    section in dev-subdev.rst
- Implementation:
  - As noted by Andrey, V4L2_FL_* are meant to be used as bitmasks. Use
    test_bit()/set_bit() as the rest of the v4l2 core does. It's a bit an
    overkill compared to use plain BIT() as noted by Sakari but I preferred
    consistency with the rest of the core
  - Make v4l2_device_register_subdev_nodes() and
    v4l2_device_register_ro_subdev_nodes() to v4l2-device.h and make them
    inline functions. Documentation style has been copied from other functions
    with similar implementations, such as __video_register_device() in
    v4l2-dev.h

Hans Verkuil (2):
  v4l2-subdev: add VIDIOC_SUBDEV_QUERYCAP ioctl
  v4l: document VIDIOC_SUBDEV_QUERYCAP

Jacopo Mondi (4):
  Documentation: media: Update sub-device API intro
  Documentation: media: Document read-only subdevice
  media: v4l2-dev: Add v4l2_device_register_ro_subdev_node()
  media: v4l2-subdev: Assume V4L2_SUBDEV_API is selected

 .../driver-api/media/v4l2-subdev.rst          |  53 +++++++-
 .../userspace-api/media/v4l/dev-subdev.rst    |   5 +
 .../userspace-api/media/v4l/user-func.rst     |   1 +
 .../media/v4l/vidioc-g-dv-timings.rst         |   6 +
 .../userspace-api/media/v4l/vidioc-g-std.rst  |   6 +
 .../media/v4l/vidioc-subdev-g-crop.rst        |   9 ++
 .../media/v4l/vidioc-subdev-g-fmt.rst         |   8 ++
 .../v4l/vidioc-subdev-g-frame-interval.rst    |   8 ++
 .../media/v4l/vidioc-subdev-g-selection.rst   |   8 ++
 .../media/v4l/vidioc-subdev-querycap.rst      | 114 ++++++++++++++++++
 drivers/media/v4l2-core/v4l2-device.c         |   7 +-
 drivers/media/v4l2-core/v4l2-subdev.c         |  41 +++++--
 include/media/v4l2-dev.h                      |   7 ++
 include/media/v4l2-device.h                   |  50 +++++++-
 include/uapi/linux/v4l2-subdev.h              |  15 +++
 15 files changed, 322 insertions(+), 16 deletions(-)
 create mode 100644 Documentation/userspace-api/media/v4l/vidioc-subdev-querycap.rst

--
2.26.1

[PATCH v5 1/6] Documentation: media: Update sub-device API intro

[Jacopo Mondi]

Update the V4L2 sub-device userspace API introduction to provide more
details on why complex devices might want to register devnodes for the
connected subdevices.

Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
---
 Documentation/driver-api/media/v4l2-subdev.rst | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/Documentation/driver-api/media/v4l2-subdev.rst b/Documentation/driver-api/media/v4l2-subdev.rst
index 29e07e23f888..41ccb3e5c707 100644
--- a/Documentation/driver-api/media/v4l2-subdev.rst
+++ b/Documentation/driver-api/media/v4l2-subdev.rst
@@ -275,8 +275,13 @@ system the .unbind() method is called. All three callbacks are optional.
 V4L2 sub-device userspace API
 -----------------------------
 
-Beside exposing a kernel API through the :c:type:`v4l2_subdev_ops` structure,
-V4L2 sub-devices can also be controlled directly by userspace applications.
+Bridge drivers traditionally expose one or multiple video nodes to userspace,
+and control subdevices through the :c:type:`v4l2_subdev_ops` operations in
+response to video node operations. This hides the complexity of the underlying
+hardware from applications. For complex devices, finer-grained control of the
+device than what the video nodes offer may be required. In those cases, bridge
+drivers that implement :ref:`the media controller API <media_controller>` may
+opt for making the subdevice operations directly accessible from userpace.
 
 Device nodes named ``v4l-subdev``\ *X* can be created in ``/dev`` to access
 sub-devices directly. If a sub-device supports direct userspace configuration
-- 
2.26.1

[PATCH v5 2/6] Documentation: media: Document read-only subdevice

[Jacopo Mondi]

Document a new kAPI function to register subdev device nodes in read only
mode and for each affected ioctl report how access is restricted.

Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
---
 .../driver-api/media/v4l2-subdev.rst          | 44 +++++++++++++++++++
 .../userspace-api/media/v4l/dev-subdev.rst    |  5 +++
 .../media/v4l/vidioc-g-dv-timings.rst         |  6 +++
 .../userspace-api/media/v4l/vidioc-g-std.rst  |  6 +++
 .../media/v4l/vidioc-subdev-g-crop.rst        |  9 ++++
 .../media/v4l/vidioc-subdev-g-fmt.rst         |  8 ++++
 .../v4l/vidioc-subdev-g-frame-interval.rst    |  8 ++++
 .../media/v4l/vidioc-subdev-g-selection.rst   |  8 ++++
 8 files changed, 94 insertions(+)

diff --git a/Documentation/driver-api/media/v4l2-subdev.rst b/Documentation/driver-api/media/v4l2-subdev.rst
index 41ccb3e5c707..6ced2381952a 100644
--- a/Documentation/driver-api/media/v4l2-subdev.rst
+++ b/Documentation/driver-api/media/v4l2-subdev.rst
@@ -332,6 +332,50 @@ Private ioctls
 	All ioctls not in the above list are passed directly to the sub-device
 	driver through the core::ioctl operation.
 
+Read-only sub-device userspace API
+----------------------------------
+
+Bridge drivers that control their connected subdevices through direct calls to
+the kernel API realized by :c:type:`v4l2_subdev_ops` structure do not usually
+want userspace to be able to change the same parameters through the subdevice
+device node and thus do not usually register any.
+
+It is sometimes useful to report to userspace the current subdevice
+configuration through a read-only API, that does not permit applications to
+change to the device parameters but allows interfacing to the subdevice device
+node to inspect them.
+
+For instance, to implement cameras based on computational photography, userspace
+needs to know the detailed camera sensor configuration (in terms of skipping,
+binning, cropping and scaling) for each supported output resolution. To support
+such use cases, bridge drivers may expose the subdevice operations to userspace
+through a read-only API.
+
+To create a read-only device node for all the subdevices registered with the
+``V4L2_SUBDEV_FL_HAS_DEVNODE`` set, the :c:type:`v4l2_device` driver should call
+:c:func:`v4l2_device_register_ro_subdev_nodes`.
+
+Access to the following ioctls for userspace applications is restricted on
+sub-device device nodes registered with
+:c:func:`v4l2_device_register_ro_subdev_nodes`.
+
+``VIDIOC_SUBDEV_S_FMT``,
+``VIDIOC_SUBDEV_S_CROP``,
+``VIDIOC_SUBDEV_S_SELECTION``:
+
+	These ioctls are only allowed on a read-only subdevice device node
+	for the :ref:`V4L2_SUBDEV_FORMAT_TRY <v4l2-subdev-format-whence>`
+	formats and selection rectangles.
+
+``VIDIOC_SUBDEV_S_FRAME_INTERVAL``,
+``VIDIOC_SUBDEV_S_DV_TIMINGS``,
+``VIDIOC_SUBDEV_S_STD``:
+
+	These ioctls are not allowed on a read-only subdevice node.
+
+In case the ioctl is not allowed, or the format to modify is set to
+``V4L2_SUBDEV_FORMAT_ACTIVE``, the core returns a negative error code and
+the errno variable is set to ``-EPERM``.
 
 I2C sub-device drivers
 ----------------------
diff --git a/Documentation/userspace-api/media/v4l/dev-subdev.rst b/Documentation/userspace-api/media/v4l/dev-subdev.rst
index 0c1a5f50ee21..134d2fb909fa 100644
--- a/Documentation/userspace-api/media/v4l/dev-subdev.rst
+++ b/Documentation/userspace-api/media/v4l/dev-subdev.rst
@@ -39,6 +39,11 @@ will feature a character device node on which ioctls can be called to
 Sub-device character device nodes, conventionally named
 ``/dev/v4l-subdev*``, use major number 81.
 
+Drivers may opt to limit the sub-device character devices to only expose
+operations that do not modify the device state. In such a case the sub-devices
+are referred to as ``read-only`` in the rest of this documentation, and the
+related restrictions are documented in individual ioctls.
+
 
 Controls
 ========
diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-dv-timings.rst b/Documentation/userspace-api/media/v4l/vidioc-g-dv-timings.rst
index 84806a893cb7..9a035a4ea0f0 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-g-dv-timings.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-g-dv-timings.rst
@@ -57,6 +57,10 @@ pointer to the struct :c:type:`v4l2_dv_timings`
 structure as argument. If the ioctl is not supported or the timing
 values are not correct, the driver returns ``EINVAL`` error code.
 
+Calling ``VIDIOC_SUBDEV_S_DV_TIMINGS`` on a subdev device node that has been
+registered in read-only mode is not allowed. An error is returned and the errno
+variable is set to ``-EPERM``.
+
 The ``linux/v4l2-dv-timings.h`` header can be used to get the timings of
 the formats in the :ref:`cea861` and :ref:`vesadmt` standards. If
 the current input or output does not support DV timings (e.g. if
@@ -81,6 +85,8 @@ ENODATA
 EBUSY
     The device is busy and therefore can not change the timings.
 
+EPERM
+    ``VIDIOC_SUBDEV_S_DV_TIMINGS`` has been called on a read-only subdevice.
 
 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
 
diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-std.rst b/Documentation/userspace-api/media/v4l/vidioc-g-std.rst
index b0bdb719d405..6d8cb7f29ac6 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-g-std.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-g-std.rst
@@ -66,6 +66,9 @@ video timings (e.g. if :ref:`VIDIOC_ENUMINPUT`
 does not set the ``V4L2_IN_CAP_STD`` flag), then ``ENODATA`` error code is
 returned.
 
+Calling ``VIDIOC_SUBDEV_S_STD`` on a subdev device node that has been registered
+in read-only mode is not allowed. An error is returned and the errno variable is
+set to ``-EPERM``.
 
 Return Value
 ============
@@ -79,3 +82,6 @@ EINVAL
 
 ENODATA
     Standard video timings are not supported for this input or output.
+
+EPERM
+    ``VIDIOC_SUBDEV_S_STD`` has been called on a read-only subdevice.
diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-crop.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-crop.rst
index 8d9fc13015a6..615e3efdf935 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-crop.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-crop.rst
@@ -73,6 +73,11 @@ crop rectangles and stored in the sub-device file handle. Two
 applications querying the same sub-device would thus not interact with
 each other.
 
+If the subdev device node has been registered in read-only mode, calls to
+``VIDIOC_SUBDEV_S_CROP`` are only valid if the ``which`` field is set to
+``V4L2_SUBDEV_FORMAT_TRY``, otherwise an error is returned and the errno
+variable is set to ``-EPERM``.
+
 Drivers must not return an error solely because the requested crop
 rectangle doesn't match the device capabilities. They must instead
 modify the rectangle to match what the hardware can provide. The
@@ -123,3 +128,7 @@ EINVAL
     references a non-existing pad, the ``which`` field references a
     non-existing format, or cropping is not supported on the given
     subdev pad.
+
+EPERM
+    The ``VIDIOC_SUBDEV_S_CROP`` ioctl has been called on a read-only subdevice
+    and the ``which`` field is set to ``V4L2_SUBDEV_FORMAT_ACTIVE``.
diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-fmt.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-fmt.rst
index 69d60e18664b..909ee9f90867 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-fmt.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-fmt.rst
@@ -78,6 +78,11 @@ current links configuration or sub-device controls value. For instance,
 a low-pass noise filter might crop pixels at the frame boundaries,
 modifying its output frame size.
 
+If the subdev device node has been registered in read-only mode, calls to
+``VIDIOC_SUBDEV_S_FMT`` are only valid if the ``which`` field is set to
+``V4L2_SUBDEV_FORMAT_TRY``, otherwise an error is returned and the errno
+variable is set to ``-EPERM``.
+
 Drivers must not return an error solely because the requested format
 doesn't match the device capabilities. They must instead modify the
 format to match what the hardware can provide. The modified format
@@ -146,6 +151,9 @@ EINVAL
     ``pad`` references a non-existing pad, or the ``which`` field
     references a non-existing format.
 
+EPERM
+    The ``VIDIOC_SUBDEV_S_FMT`` ioctl has been called on a read-only subdevice
+    and the ``which`` field is set to ``V4L2_SUBDEV_FORMAT_ACTIVE``.
 
 ============
 
diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-frame-interval.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-frame-interval.rst
index b61baaf11624..51e1bff797f0 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-frame-interval.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-frame-interval.rst
@@ -65,6 +65,10 @@ struct
 contains the current frame interval as would be returned by a
 ``VIDIOC_SUBDEV_G_FRAME_INTERVAL`` call.
 
+Calling ``VIDIOC_SUBDEV_S_FRAME_INTERVAL`` on a subdev device node that has been
+registered in read-only mode is not allowed. An error is returned and the errno
+variable is set to ``-EPERM``.
+
 Drivers must not return an error solely because the requested interval
 doesn't match the device capabilities. They must instead modify the
 interval to match what the hardware can provide. The modified interval
@@ -118,3 +122,7 @@ EINVAL
     :c:type:`v4l2_subdev_frame_interval`
     ``pad`` references a non-existing pad, or the pad doesn't support
     frame intervals.
+
+EPERM
+    The ``VIDIOC_SUBDEV_S_FRAME_INTERVAL`` ioctl has been called on a read-only
+    subdevice.
diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-selection.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-selection.rst
index 981c95df2dec..06c9553ac48f 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-selection.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-selection.rst
@@ -53,6 +53,10 @@ function of the crop API, and more, are supported by the selections API.
 See :ref:`subdev` for more information on how each selection target
 affects the image processing pipeline inside the subdevice.
 
+If the subdev device node has been registered in read-only mode, calls to
+``VIDIOC_SUBDEV_S_SELECTION`` are only valid if the ``which`` field is set to
+``V4L2_SUBDEV_FORMAT_TRY``, otherwise an error is returned and the errno
+variable is set to ``-EPERM``.
 
 Types of selection targets
 --------------------------
@@ -123,3 +127,7 @@ EINVAL
     ``pad`` references a non-existing pad, the ``which`` field
     references a non-existing format, or the selection target is not
     supported on the given subdev pad.
+
+EPERM
+    The ``VIDIOC_SUBDEV_S_SELECTION`` ioctl has been called on a read-only
+    subdevice and the ``which`` field is set to ``V4L2_SUBDEV_FORMAT_ACTIVE``.
-- 
2.26.1

[PATCH v5 3/6] media: v4l2-dev: Add v4l2_device_register_ro_subdev_node()

[Jacopo Mondi]

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.

Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
---
 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           | 50 ++++++++++++++++++++++++---
 4 files changed, 77 insertions(+), 6 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-device.c b/drivers/media/v4l2-core/v4l2-device.c
index c69941214bb2..de4287251a89 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_SUBDEV_RO_DEVNODE, &vdev->flags);
 		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..1dc263c2ca0a 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_SUBDEV_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..ad2d41952442 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_SUBDEV_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_SUBDEV_RO_DEVNODE	= 3,
 };
 
 /* Priority helper functions */
diff --git a/include/media/v4l2-device.h b/include/media/v4l2-device.h
index 7c912b7d2870..64ec4de948e9 100644
--- a/include/media/v4l2-device.h
+++ b/include/media/v4l2-device.h
@@ -174,14 +174,56 @@ 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)
+{
+#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
+	return __v4l2_device_register_subdev_nodes(v4l2_dev, false);
+#else
+	return 0;
+#endif
+}
+
+/**
+ * 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)
+{
+#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
+	return __v4l2_device_register_subdev_nodes(v4l2_dev, true);
+#else
+	return 0;
+#endif
+}
 
 /**
  * v4l2_subdev_notify - Sends a notification to v4l2_device.
-- 
2.26.1

[PATCH v5 4/6] media: v4l2-subdev: Assume V4L2_SUBDEV_API is selected

[Jacopo Mondi]

A sub-device device node can be registered in user space only if the
CONFIG_V4L2_SUBDEV_API Kconfig option is selected.

Remove checks from the v4l2-subdev file handle open/close functions and
ioctl handler as they are only accessible if a device node was registered
to user space in first place.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
---
 drivers/media/v4l2-core/v4l2-subdev.c | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 1dc263c2ca0a..f3fe515b8ccb 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -24,22 +24,19 @@
 
 static int subdev_fh_init(struct v4l2_subdev_fh *fh, struct v4l2_subdev *sd)
 {
-#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
 	if (sd->entity.num_pads) {
 		fh->pad = v4l2_subdev_alloc_pad_config(sd);
 		if (fh->pad == NULL)
 			return -ENOMEM;
 	}
-#endif
+
 	return 0;
 }
 
 static void subdev_fh_free(struct v4l2_subdev_fh *fh)
 {
-#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
 	v4l2_subdev_free_pad_config(fh->pad);
 	fh->pad = NULL;
-#endif
 }
 
 static int subdev_open(struct file *file)
@@ -329,10 +326,8 @@ static long subdev_do_ioctl(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 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_SUBDEV_RO_DEVNODE, &vdev->flags);
-#endif
 	int rval;
 
 	switch (cmd) {
@@ -466,7 +461,6 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 		return ret;
 	}
 
-#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
 	case VIDIOC_SUBDEV_G_FMT: {
 		struct v4l2_subdev_format *format = arg;
 
@@ -646,7 +640,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 
 	case VIDIOC_SUBDEV_QUERYSTD:
 		return v4l2_subdev_call(sd, video, querystd, arg);
-#endif
+
 	default:
 		return v4l2_subdev_call(sd, core, ioctl, cmd, arg);
 	}
-- 
2.26.1

[PATCH v5 5/6] v4l2-subdev: add VIDIOC_SUBDEV_QUERYCAP ioctl

[Jacopo Mondi]

From: Hans Verkuil <hans.verkuil@cisco.com>

While normal video/radio/vbi/swradio nodes have a proper QUERYCAP ioctl
that apps can call to determine that it is indeed a V4L2 device, there
is currently no equivalent for v4l-subdev nodes. Adding this ioctl will
solve that, and it will allow utilities like v4l2-compliance to be used
with these devices as well.

SUBDEV_QUERYCAP currently returns the version and subdev_caps of the
subdevice. Define as the initial set of subdev_caps the read-only or
read/write flags, to signal to userspace which set of IOCTLs are
available on the subdevice.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
---
 drivers/media/v4l2-core/v4l2-subdev.c | 12 ++++++++++++
 include/uapi/linux/v4l2-subdev.h      | 15 +++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index f3fe515b8ccb..b8c0071aa4d0 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -15,6 +15,7 @@
 #include <linux/types.h>
 #include <linux/videodev2.h>
 #include <linux/export.h>
+#include <linux/version.h>
 
 #include <media/v4l2-ctrls.h>
 #include <media/v4l2-device.h>
@@ -331,6 +332,17 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 	int rval;
 
 	switch (cmd) {
+	case VIDIOC_SUBDEV_QUERYCAP: {
+		struct v4l2_subdev_capability *cap = arg;
+
+		memset(cap, 0, sizeof(*cap));
+		cap->version = LINUX_VERSION_CODE;
+		cap->subdev_caps |= ro_subdev ? V4L2_SUBDEV_CAP_RO_SUBDEV
+					      : V4L2_SUBDEV_CAP_RW_SUBDEV;
+
+		return 0;
+	}
+
 	case VIDIOC_QUERYCTRL:
 		/*
 		 * TODO: this really should be folded into v4l2_queryctrl (this
diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
index 03970ce30741..89dc8f2ba6b3 100644
--- a/include/uapi/linux/v4l2-subdev.h
+++ b/include/uapi/linux/v4l2-subdev.h
@@ -155,9 +155,24 @@ struct v4l2_subdev_selection {
 	__u32 reserved[8];
 };
 
+/**
+ * struct v4l2_subdev_capability - subdev capabilities
+ * @device_caps: the subdev capabilities, see V4L2_SUBDEV_CAP_*.
+ */
+struct v4l2_subdev_capability {
+	__u32 version;
+	__u32 subdev_caps;
+};
+
+/* The v4l2 sub-device video device node is registered in read-only mode. */
+#define V4L2_SUBDEV_CAP_RO_SUBDEV		BIT(0)
+/* The v4l2 sub-device video device node is registered in read/write mode. */
+#define V4L2_SUBDEV_CAP_RW_SUBDEV		BIT(1)
+
 /* Backwards compatibility define --- to be removed */
 #define v4l2_subdev_edid v4l2_edid
 
+#define VIDIOC_SUBDEV_QUERYCAP			_IOR('V',  0, struct v4l2_subdev_capability)
 #define VIDIOC_SUBDEV_G_FMT			_IOWR('V',  4, struct v4l2_subdev_format)
 #define VIDIOC_SUBDEV_S_FMT			_IOWR('V',  5, struct v4l2_subdev_format)
 #define VIDIOC_SUBDEV_G_FRAME_INTERVAL		_IOWR('V', 21, struct v4l2_subdev_frame_interval)
-- 
2.26.1

[PATCH v5 6/6] v4l: document VIDIOC_SUBDEV_QUERYCAP

[Jacopo Mondi]

From: Hans Verkuil <hans.verkuil@cisco.com>

Add documentation for the new VIDIOC_SUBDEV_QUERYCAP ioctl.

Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
---
 .../userspace-api/media/v4l/user-func.rst     |   1 +
 .../media/v4l/vidioc-subdev-querycap.rst      | 114 ++++++++++++++++++
 2 files changed, 115 insertions(+)
 create mode 100644 Documentation/userspace-api/media/v4l/vidioc-subdev-querycap.rst

diff --git a/Documentation/userspace-api/media/v4l/user-func.rst b/Documentation/userspace-api/media/v4l/user-func.rst
index f235f88efe89..bf77c842718e 100644
--- a/Documentation/userspace-api/media/v4l/user-func.rst
+++ b/Documentation/userspace-api/media/v4l/user-func.rst
@@ -78,6 +78,7 @@ Function Reference
     vidioc-subdev-g-fmt
     vidioc-subdev-g-frame-interval
     vidioc-subdev-g-selection
+    vidioc-subdev-querycap
     vidioc-subscribe-event
     func-mmap
     func-munmap
diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-querycap.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-querycap.rst
new file mode 100644
index 000000000000..1ab5c808d9b4
--- /dev/null
+++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-querycap.rst
@@ -0,0 +1,114 @@
+.. Permission is granted to copy, distribute and/or modify this
+.. document under the terms of the GNU Free Documentation License,
+.. Version 1.1 or any later version published by the Free Software
+.. Foundation, with no Invariant Sections, no Front-Cover Texts
+.. and no Back-Cover Texts. A copy of the license is included at
+.. Documentation/userspace-api/media/fdl-appendix.rst.
+..
+.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
+
+.. _VIDIOC_SUBDEV_QUERYCAP:
+
+****************************
+ioctl VIDIOC_SUBDEV_QUERYCAP
+****************************
+
+Name
+====
+
+VIDIOC_SUBDEV_QUERYCAP - Query sub-device capabilities
+
+
+Synopsis
+========
+
+.. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_QUERYCAP, struct v4l2_subdev_capability *argp )
+    :name: VIDIOC_SUBDEV_QUERYCAP
+
+
+Arguments
+=========
+
+``fd``
+    File descriptor returned by :ref:`open() <func-open>`.
+
+``argp``
+    Pointer to struct :c:type:`v4l2_subdev_capability`.
+
+
+Description
+===========
+
+All V4L2 sub-devices support the ``VIDIOC_SUBDEV_QUERYCAP`` ioctl. It is used to
+identify kernel devices compatible with this specification and to obtain
+information about driver and hardware capabilities. The ioctl takes a pointer to
+a struct :c:type:`v4l2_subdev_capability` which is filled by the driver. When
+the driver is not compatible with this specification the ioctl returns
+``ENOTTY`` error code.
+
+.. tabularcolumns:: |p{1.5cm}|p{2.5cm}|p{13cm}|
+
+.. c:type:: v4l2_subdev_capability
+
+.. flat-table:: struct v4l2_subdev_capability
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       3 4 20
+
+    * - __u32
+      - ``version``
+      - Version number of the driver.
+
+	The version reported is provided by the V4L2 subsystem following the
+	kernel numbering scheme. However, it may not always return the same
+	version as the kernel if, for example, a stable or
+	distribution-modified kernel uses the V4L2 stack from a newer kernel.
+
+	The version number is formatted using the ``KERNEL_VERSION()``
+	macro:
+    * - :cspan:`2`
+
+	``#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))``
+
+	``__u32 version = KERNEL_VERSION(0, 8, 1);``
+
+	``printf ("Version: %u.%u.%u\\n",``
+
+	``(version >> 16) & 0xFF, (version >> 8) & 0xFF, version & 0xFF);``
+    * - __u32
+      - ``subdev_caps``
+      - Sub-device capabilities of the opened device, see
+	:ref:`subdevice-capabilities`.
+
+.. tabularcolumns:: |p{6cm}|p{2.2cm}|p{8.8cm}|
+
+.. _subdevice-capabilities:
+
+.. cssclass:: longtable
+
+.. flat-table:: Sub-Device Capabilities Flags
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       3 1 4
+
+    * - V4L2_SUBDEV_CAP_RO_SUBDEV
+      - 0x00000001
+      - The sub-device device node is registered in read-only mode.
+	Access to the sub-device ioctls that modify the device state is
+	restricted. Refer to each individual subdevice ioctl documentation
+	for a description of which restrictions apply to a read-only sub-device.
+
+    * - V4L2_SUBDEV_CAP_RW_SUBDEV
+      - 0x00000002
+      - The sub-device device node is registered in read/write mode, all the
+	subdevice ioctls are accessible from userspace.
+
+Return Value
+============
+
+On success 0 is returned, on error -1 and the ``errno`` variable is set
+appropriately. The generic error codes are described at the
+:ref:`Generic Error Codes <gen-errors>` chapter.
+
+ENOTTY
+    The device node is not a V4L2 sub-device.
-- 
2.26.1

Re: [PATCH v5 4/6] media: v4l2-subdev: Assume V4L2_SUBDEV_API is selected

[Sakari Ailus]

Hi Jacopo,

On Tue, Apr 28, 2020 at 11:06:07PM +0200, Jacopo Mondi wrote:
> A sub-device device node can be registered in user space only if the
> CONFIG_V4L2_SUBDEV_API Kconfig option is selected.
> 
> Remove checks from the v4l2-subdev file handle open/close functions and
> ioctl handler as they are only accessible if a device node was registered
> to user space in first place.

Is there other motivation with this than clean up things a little?

The change increases the binary size marginally if the Kconfig option is
disabled.

> 
> Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
> ---
>  drivers/media/v4l2-core/v4l2-subdev.c | 10 ++--------
>  1 file changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index 1dc263c2ca0a..f3fe515b8ccb 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -24,22 +24,19 @@
>  
>  static int subdev_fh_init(struct v4l2_subdev_fh *fh, struct v4l2_subdev *sd)
>  {
> -#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
>  	if (sd->entity.num_pads) {
>  		fh->pad = v4l2_subdev_alloc_pad_config(sd);
>  		if (fh->pad == NULL)
>  			return -ENOMEM;
>  	}
> -#endif
> +
>  	return 0;
>  }
>  
>  static void subdev_fh_free(struct v4l2_subdev_fh *fh)
>  {
> -#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
>  	v4l2_subdev_free_pad_config(fh->pad);
>  	fh->pad = NULL;
> -#endif
>  }
>  
>  static int subdev_open(struct file *file)
> @@ -329,10 +326,8 @@ static long subdev_do_ioctl(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 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_SUBDEV_RO_DEVNODE, &vdev->flags);
> -#endif
>  	int rval;
>  
>  	switch (cmd) {
> @@ -466,7 +461,6 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
>  		return ret;
>  	}
>  
> -#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
>  	case VIDIOC_SUBDEV_G_FMT: {
>  		struct v4l2_subdev_format *format = arg;
>  
> @@ -646,7 +640,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
>  
>  	case VIDIOC_SUBDEV_QUERYSTD:
>  		return v4l2_subdev_call(sd, video, querystd, arg);
> -#endif
> +
>  	default:
>  		return v4l2_subdev_call(sd, core, ioctl, cmd, arg);
>  	}
> -- 
> 2.26.1
> 

-- 
Sakari Ailus

Re: [PATCH v5 5/6] v4l2-subdev: add VIDIOC_SUBDEV_QUERYCAP ioctl

[Sakari Ailus]

Hi Jacopo,

On Tue, Apr 28, 2020 at 11:06:08PM +0200, Jacopo Mondi wrote:
> From: Hans Verkuil <hans.verkuil@cisco.com>
> 
> While normal video/radio/vbi/swradio nodes have a proper QUERYCAP ioctl
> that apps can call to determine that it is indeed a V4L2 device, there
> is currently no equivalent for v4l-subdev nodes. Adding this ioctl will
> solve that, and it will allow utilities like v4l2-compliance to be used
> with these devices as well.
> 
> SUBDEV_QUERYCAP currently returns the version and subdev_caps of the
> subdevice. Define as the initial set of subdev_caps the read-only or
> read/write flags, to signal to userspace which set of IOCTLs are
> available on the subdevice.
> 
> Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
> Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
> ---
>  drivers/media/v4l2-core/v4l2-subdev.c | 12 ++++++++++++
>  include/uapi/linux/v4l2-subdev.h      | 15 +++++++++++++++
>  2 files changed, 27 insertions(+)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index f3fe515b8ccb..b8c0071aa4d0 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -15,6 +15,7 @@
>  #include <linux/types.h>
>  #include <linux/videodev2.h>
>  #include <linux/export.h>
> +#include <linux/version.h>
>  
>  #include <media/v4l2-ctrls.h>
>  #include <media/v4l2-device.h>
> @@ -331,6 +332,17 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
>  	int rval;
>  
>  	switch (cmd) {
> +	case VIDIOC_SUBDEV_QUERYCAP: {
> +		struct v4l2_subdev_capability *cap = arg;
> +
> +		memset(cap, 0, sizeof(*cap));
> +		cap->version = LINUX_VERSION_CODE;
> +		cap->subdev_caps |= ro_subdev ? V4L2_SUBDEV_CAP_RO_SUBDEV
> +					      : V4L2_SUBDEV_CAP_RW_SUBDEV;
> +
> +		return 0;
> +	}
> +
>  	case VIDIOC_QUERYCTRL:
>  		/*
>  		 * TODO: this really should be folded into v4l2_queryctrl (this
> diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
> index 03970ce30741..89dc8f2ba6b3 100644
> --- a/include/uapi/linux/v4l2-subdev.h
> +++ b/include/uapi/linux/v4l2-subdev.h
> @@ -155,9 +155,24 @@ struct v4l2_subdev_selection {
>  	__u32 reserved[8];
>  };
>  
> +/**
> + * struct v4l2_subdev_capability - subdev capabilities
> + * @device_caps: the subdev capabilities, see V4L2_SUBDEV_CAP_*.
> + */
> +struct v4l2_subdev_capability {
> +	__u32 version;
> +	__u32 subdev_caps;

How do you intend to address additional fields being added to the struct in
the future? Something else than what's been done in V4L2 traditionally?

> +};
> +
> +/* The v4l2 sub-device video device node is registered in read-only mode. */
> +#define V4L2_SUBDEV_CAP_RO_SUBDEV		BIT(0)
> +/* The v4l2 sub-device video device node is registered in read/write mode. */
> +#define V4L2_SUBDEV_CAP_RW_SUBDEV		BIT(1)
> +
>  /* Backwards compatibility define --- to be removed */
>  #define v4l2_subdev_edid v4l2_edid
>  
> +#define VIDIOC_SUBDEV_QUERYCAP			_IOR('V',  0, struct v4l2_subdev_capability)
>  #define VIDIOC_SUBDEV_G_FMT			_IOWR('V',  4, struct v4l2_subdev_format)
>  #define VIDIOC_SUBDEV_S_FMT			_IOWR('V',  5, struct v4l2_subdev_format)
>  #define VIDIOC_SUBDEV_G_FRAME_INTERVAL		_IOWR('V', 21, struct v4l2_subdev_frame_interval)

-- 
Regards,

Sakari Ailus

Re: [PATCH v5 4/6] media: v4l2-subdev: Assume V4L2_SUBDEV_API is selected

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 9873 bytes --]

Hi Jacopo,

I love your patch! Yet something to improve:

[auto build test ERROR on linuxtv-media/master]
[also build test ERROR on linus/master v5.7-rc3 next-20200428]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Jacopo-Mondi/media-Register-read-only-sub-dev-devnode/20200429-062133
base:   git://linuxtv.org/media_tree.git master
config: arm-at91_dt_defconfig (attached as .config)
compiler: arm-linux-gnueabi-gcc (GCC) 9.3.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day GCC_VERSION=9.3.0 make.cross ARCH=arm 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   drivers/media/v4l2-core/v4l2-subdev.c: In function 'subdev_fh_init':
>> drivers/media/v4l2-core/v4l2-subdev.c:28:5: error: 'struct v4l2_subdev_fh' has no member named 'pad'
      28 |   fh->pad = v4l2_subdev_alloc_pad_config(sd);
         |     ^~
   drivers/media/v4l2-core/v4l2-subdev.c:29:9: error: 'struct v4l2_subdev_fh' has no member named 'pad'
      29 |   if (fh->pad == NULL)
         |         ^~
   drivers/media/v4l2-core/v4l2-subdev.c: In function 'subdev_fh_free':
   drivers/media/v4l2-core/v4l2-subdev.c:38:32: error: 'struct v4l2_subdev_fh' has no member named 'pad'
      38 |  v4l2_subdev_free_pad_config(fh->pad);
         |                                ^~
   drivers/media/v4l2-core/v4l2-subdev.c:39:4: error: 'struct v4l2_subdev_fh' has no member named 'pad'
      39 |  fh->pad = NULL;
         |    ^~
   In file included from include/media/v4l2-device.h:13,
                    from drivers/media/v4l2-core/v4l2-subdev.c:20:
   drivers/media/v4l2-core/v4l2-subdev.c: In function 'subdev_do_ioctl':
   drivers/media/v4l2-core/v4l2-subdev.c:469:54: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     469 |   return v4l2_subdev_call(sd, pad, get_fmt, subdev_fh->pad, format);
         |                                                      ^~
   include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
    1111 |        __sd, ##args); \
         |                ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:469:54: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     469 |   return v4l2_subdev_call(sd, pad, get_fmt, subdev_fh->pad, format);
         |                                                      ^~
   include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
    1113 |    __result = __sd->ops->o->f(__sd, ##args); \
         |                                       ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:480:54: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     480 |   return v4l2_subdev_call(sd, pad, set_fmt, subdev_fh->pad, format);
         |                                                      ^~
   include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
    1111 |        __sd, ##args); \
         |                ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:480:54: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     480 |   return v4l2_subdev_call(sd, pad, set_fmt, subdev_fh->pad, format);
         |                                                      ^~
   include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
    1113 |    __result = __sd->ops->o->f(__sd, ##args); \
         |                                       ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:494:37: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     494 |    sd, pad, get_selection, subdev_fh->pad, &sel);
         |                                     ^~
   include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
    1111 |        __sd, ##args); \
         |                ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:494:37: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     494 |    sd, pad, get_selection, subdev_fh->pad, &sel);
         |                                     ^~
   include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
    1113 |    __result = __sd->ops->o->f(__sd, ##args); \
         |                                       ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:516:37: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     516 |    sd, pad, set_selection, subdev_fh->pad, &sel);
         |                                     ^~
   include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
    1111 |        __sd, ##args); \
         |                ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:516:37: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     516 |    sd, pad, set_selection, subdev_fh->pad, &sel);
         |                                     ^~
   include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
    1113 |    __result = __sd->ops->o->f(__sd, ##args); \
         |                                       ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:527:61: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     527 |   return v4l2_subdev_call(sd, pad, enum_mbus_code, subdev_fh->pad,
         |                                                             ^~
   include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
    1111 |        __sd, ##args); \
         |                ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:527:61: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     527 |   return v4l2_subdev_call(sd, pad, enum_mbus_code, subdev_fh->pad,
         |                                                             ^~
   include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
    1113 |    __result = __sd->ops->o->f(__sd, ##args); \
         |                                       ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:535:62: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     535 |   return v4l2_subdev_call(sd, pad, enum_frame_size, subdev_fh->pad,
         |                                                              ^~
   include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
    1111 |        __sd, ##args); \
         |                ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:535:62: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     535 |   return v4l2_subdev_call(sd, pad, enum_frame_size, subdev_fh->pad,
         |                                                              ^~
   include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
    1113 |    __result = __sd->ops->o->f(__sd, ##args); \
         |                                       ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:560:66: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     560 |   return v4l2_subdev_call(sd, pad, enum_frame_interval, subdev_fh->pad,
         |                                                                  ^~
   include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
    1111 |        __sd, ##args); \
         |                ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:560:66: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     560 |   return v4l2_subdev_call(sd, pad, enum_frame_interval, subdev_fh->pad,
         |                                                                  ^~
   include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
    1113 |    __result = __sd->ops->o->f(__sd, ##args); \
         |                                       ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:569:37: error: 'struct v4l2_subdev_fh' has no member named 'pad'

vim +28 drivers/media/v4l2-core/v4l2-subdev.c

2096a5dcf9704f drivers/media/video/v4l2-subdev.c     Laurent Pinchart  2009-12-09  24  
7cd5a16b22af7d drivers/media/video/v4l2-subdev.c     Stanimir Varbanov 2010-05-21  25  static int subdev_fh_init(struct v4l2_subdev_fh *fh, struct v4l2_subdev *sd)
7cd5a16b22af7d drivers/media/video/v4l2-subdev.c     Stanimir Varbanov 2010-05-21  26  {
9b02cbb3ede89b drivers/media/v4l2-core/v4l2-subdev.c Laurent Pinchart  2015-04-24  27  	if (sd->entity.num_pads) {
9b02cbb3ede89b drivers/media/v4l2-core/v4l2-subdev.c Laurent Pinchart  2015-04-24 @28  		fh->pad = v4l2_subdev_alloc_pad_config(sd);
ae184cda8d0eeb drivers/media/video/v4l2-subdev.c     Sakari Ailus      2011-10-14  29  		if (fh->pad == NULL)
7cd5a16b22af7d drivers/media/video/v4l2-subdev.c     Stanimir Varbanov 2010-05-21  30  			return -ENOMEM;
9b02cbb3ede89b drivers/media/v4l2-core/v4l2-subdev.c Laurent Pinchart  2015-04-24  31  	}
b9e6aad3939a62 drivers/media/v4l2-core/v4l2-subdev.c Jacopo Mondi      2020-04-28  32  
7cd5a16b22af7d drivers/media/video/v4l2-subdev.c     Stanimir Varbanov 2010-05-21  33  	return 0;
7cd5a16b22af7d drivers/media/video/v4l2-subdev.c     Stanimir Varbanov 2010-05-21  34  }
7cd5a16b22af7d drivers/media/video/v4l2-subdev.c     Stanimir Varbanov 2010-05-21  35  

:::::: The code at line 28 was first introduced by commit
:::::: 9b02cbb3ede89b5cd84bbe4ef493bd130d76b070 [media] v4l: subdev: Add pad config allocator and init

:::::: TO: Laurent Pinchart <laurent.pinchart@linaro.org>
:::::: CC: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 28588 bytes --]

Re: [PATCH v5 4/6] media: v4l2-subdev: Assume V4L2_SUBDEV_API is selected

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 10027 bytes --]

Hi Jacopo,

I love your patch! Yet something to improve:

[auto build test ERROR on linuxtv-media/master]
[also build test ERROR on linus/master v5.7-rc3 next-20200428]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Jacopo-Mondi/media-Register-read-only-sub-dev-devnode/20200429-062133
base:   git://linuxtv.org/media_tree.git master
config: arm-at91_dt_defconfig (attached as .config)
compiler: arm-linux-gnueabi-gcc (GCC) 9.3.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day GCC_VERSION=9.3.0 make.cross ARCH=arm 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   drivers/media/v4l2-core/v4l2-subdev.c: In function 'subdev_fh_init':
>> drivers/media/v4l2-core/v4l2-subdev.c:28:5: error: 'struct v4l2_subdev_fh' has no member named 'pad'
      28 |   fh->pad = v4l2_subdev_alloc_pad_config(sd);
         |     ^~
   drivers/media/v4l2-core/v4l2-subdev.c:29:9: error: 'struct v4l2_subdev_fh' has no member named 'pad'
      29 |   if (fh->pad == NULL)
         |         ^~
   drivers/media/v4l2-core/v4l2-subdev.c: In function 'subdev_fh_free':
   drivers/media/v4l2-core/v4l2-subdev.c:38:32: error: 'struct v4l2_subdev_fh' has no member named 'pad'
      38 |  v4l2_subdev_free_pad_config(fh->pad);
         |                                ^~
   drivers/media/v4l2-core/v4l2-subdev.c:39:4: error: 'struct v4l2_subdev_fh' has no member named 'pad'
      39 |  fh->pad = NULL;
         |    ^~
   In file included from include/media/v4l2-device.h:13,
                    from drivers/media/v4l2-core/v4l2-subdev.c:20:
   drivers/media/v4l2-core/v4l2-subdev.c: In function 'subdev_do_ioctl':
   drivers/media/v4l2-core/v4l2-subdev.c:469:54: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     469 |   return v4l2_subdev_call(sd, pad, get_fmt, subdev_fh->pad, format);
         |                                                      ^~
   include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
    1111 |        __sd, ##args); \
         |                ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:469:54: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     469 |   return v4l2_subdev_call(sd, pad, get_fmt, subdev_fh->pad, format);
         |                                                      ^~
   include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
    1113 |    __result = __sd->ops->o->f(__sd, ##args); \
         |                                       ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:480:54: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     480 |   return v4l2_subdev_call(sd, pad, set_fmt, subdev_fh->pad, format);
         |                                                      ^~
   include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
    1111 |        __sd, ##args); \
         |                ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:480:54: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     480 |   return v4l2_subdev_call(sd, pad, set_fmt, subdev_fh->pad, format);
         |                                                      ^~
   include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
    1113 |    __result = __sd->ops->o->f(__sd, ##args); \
         |                                       ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:494:37: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     494 |    sd, pad, get_selection, subdev_fh->pad, &sel);
         |                                     ^~
   include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
    1111 |        __sd, ##args); \
         |                ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:494:37: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     494 |    sd, pad, get_selection, subdev_fh->pad, &sel);
         |                                     ^~
   include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
    1113 |    __result = __sd->ops->o->f(__sd, ##args); \
         |                                       ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:516:37: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     516 |    sd, pad, set_selection, subdev_fh->pad, &sel);
         |                                     ^~
   include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
    1111 |        __sd, ##args); \
         |                ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:516:37: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     516 |    sd, pad, set_selection, subdev_fh->pad, &sel);
         |                                     ^~
   include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
    1113 |    __result = __sd->ops->o->f(__sd, ##args); \
         |                                       ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:527:61: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     527 |   return v4l2_subdev_call(sd, pad, enum_mbus_code, subdev_fh->pad,
         |                                                             ^~
   include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
    1111 |        __sd, ##args); \
         |                ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:527:61: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     527 |   return v4l2_subdev_call(sd, pad, enum_mbus_code, subdev_fh->pad,
         |                                                             ^~
   include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
    1113 |    __result = __sd->ops->o->f(__sd, ##args); \
         |                                       ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:535:62: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     535 |   return v4l2_subdev_call(sd, pad, enum_frame_size, subdev_fh->pad,
         |                                                              ^~
   include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
    1111 |        __sd, ##args); \
         |                ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:535:62: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     535 |   return v4l2_subdev_call(sd, pad, enum_frame_size, subdev_fh->pad,
         |                                                              ^~
   include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
    1113 |    __result = __sd->ops->o->f(__sd, ##args); \
         |                                       ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:560:66: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     560 |   return v4l2_subdev_call(sd, pad, enum_frame_interval, subdev_fh->pad,
         |                                                                  ^~
   include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
    1111 |        __sd, ##args); \
         |                ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:560:66: error: 'struct v4l2_subdev_fh' has no member named 'pad'
     560 |   return v4l2_subdev_call(sd, pad, enum_frame_interval, subdev_fh->pad,
         |                                                                  ^~
   include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
    1113 |    __result = __sd->ops->o->f(__sd, ##args); \
         |                                       ^~~~
   drivers/media/v4l2-core/v4l2-subdev.c:569:37: error: 'struct v4l2_subdev_fh' has no member named 'pad'

vim +28 drivers/media/v4l2-core/v4l2-subdev.c

2096a5dcf9704f drivers/media/video/v4l2-subdev.c     Laurent Pinchart  2009-12-09  24  
7cd5a16b22af7d drivers/media/video/v4l2-subdev.c     Stanimir Varbanov 2010-05-21  25  static int subdev_fh_init(struct v4l2_subdev_fh *fh, struct v4l2_subdev *sd)
7cd5a16b22af7d drivers/media/video/v4l2-subdev.c     Stanimir Varbanov 2010-05-21  26  {
9b02cbb3ede89b drivers/media/v4l2-core/v4l2-subdev.c Laurent Pinchart  2015-04-24  27  	if (sd->entity.num_pads) {
9b02cbb3ede89b drivers/media/v4l2-core/v4l2-subdev.c Laurent Pinchart  2015-04-24 @28  		fh->pad = v4l2_subdev_alloc_pad_config(sd);
ae184cda8d0eeb drivers/media/video/v4l2-subdev.c     Sakari Ailus      2011-10-14  29  		if (fh->pad == NULL)
7cd5a16b22af7d drivers/media/video/v4l2-subdev.c     Stanimir Varbanov 2010-05-21  30  			return -ENOMEM;
9b02cbb3ede89b drivers/media/v4l2-core/v4l2-subdev.c Laurent Pinchart  2015-04-24  31  	}
b9e6aad3939a62 drivers/media/v4l2-core/v4l2-subdev.c Jacopo Mondi      2020-04-28  32  
7cd5a16b22af7d drivers/media/video/v4l2-subdev.c     Stanimir Varbanov 2010-05-21  33  	return 0;
7cd5a16b22af7d drivers/media/video/v4l2-subdev.c     Stanimir Varbanov 2010-05-21  34  }
7cd5a16b22af7d drivers/media/video/v4l2-subdev.c     Stanimir Varbanov 2010-05-21  35  

:::::: The code at line 28 was first introduced by commit
:::::: 9b02cbb3ede89b5cd84bbe4ef493bd130d76b070 [media] v4l: subdev: Add pad config allocator and init

:::::: TO: Laurent Pinchart <laurent.pinchart@linaro.org>
:::::: CC: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org

[-- Attachment #2: config.gz --]
[-- Type: application/gzip, Size: 28588 bytes --]

Re: [PATCH v5 4/6] media: v4l2-subdev: Assume V4L2_SUBDEV_API is selected

[Jacopo Mondi]

Hi Sakari,

On Wed, Apr 29, 2020 at 12:26:43AM +0300, Sakari Ailus wrote:
> Hi Jacopo,
>
> On Tue, Apr 28, 2020 at 11:06:07PM +0200, Jacopo Mondi wrote:
> > A sub-device device node can be registered in user space only if the
> > CONFIG_V4L2_SUBDEV_API Kconfig option is selected.
> >
> > Remove checks from the v4l2-subdev file handle open/close functions and
> > ioctl handler as they are only accessible if a device node was registered
> > to user space in first place.
>
> Is there other motivation with this than clean up things a little?
>

I had to add yet-another #if defined and I got fed up. If you don't
have a device node registered you won't be able to access any of the
functions where the existing #if defined() where placed.

> The change increases the binary size marginally if the Kconfig option is
> disabled.
>

I see. Should we instead guard the whole file handle operations and
ioctl handler instead of having #if defined() spread inside them ? I
assume they where there as leftover, as I'm still missing the point,
give that, as said, without V4L2_SUBDEV_API, you can't register any
device node to userspace..

> >
> > Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
> > ---
> >  drivers/media/v4l2-core/v4l2-subdev.c | 10 ++--------
> >  1 file changed, 2 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> > index 1dc263c2ca0a..f3fe515b8ccb 100644
> > --- a/drivers/media/v4l2-core/v4l2-subdev.c
> > +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> > @@ -24,22 +24,19 @@
> >
> >  static int subdev_fh_init(struct v4l2_subdev_fh *fh, struct v4l2_subdev *sd)
> >  {
> > -#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
> >  	if (sd->entity.num_pads) {
> >  		fh->pad = v4l2_subdev_alloc_pad_config(sd);
> >  		if (fh->pad == NULL)
> >  			return -ENOMEM;
> >  	}
> > -#endif
> > +
> >  	return 0;
> >  }
> >
> >  static void subdev_fh_free(struct v4l2_subdev_fh *fh)
> >  {
> > -#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
> >  	v4l2_subdev_free_pad_config(fh->pad);
> >  	fh->pad = NULL;
> > -#endif
> >  }
> >
> >  static int subdev_open(struct file *file)
> > @@ -329,10 +326,8 @@ static long subdev_do_ioctl(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 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_SUBDEV_RO_DEVNODE, &vdev->flags);
> > -#endif
> >  	int rval;
> >
> >  	switch (cmd) {
> > @@ -466,7 +461,6 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> >  		return ret;
> >  	}
> >
> > -#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
> >  	case VIDIOC_SUBDEV_G_FMT: {
> >  		struct v4l2_subdev_format *format = arg;
> >
> > @@ -646,7 +640,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> >
> >  	case VIDIOC_SUBDEV_QUERYSTD:
> >  		return v4l2_subdev_call(sd, video, querystd, arg);
> > -#endif
> > +
> >  	default:
> >  		return v4l2_subdev_call(sd, core, ioctl, cmd, arg);
> >  	}
> > --
> > 2.26.1
> >
>
> --
> Sakari Ailus

Re: [PATCH v5 4/6] media: v4l2-subdev: Assume V4L2_SUBDEV_API is selected

[Jacopo Mondi]

Here it goes -.-'
I was hoping to have this going through kbuild soon

Would guarding the whole file handle operations and the ioctl handler
a best option then ?

On Wed, Apr 29, 2020 at 07:44:30AM +0800, kbuild test robot wrote:
> Hi Jacopo,
>
> I love your patch! Yet something to improve:
>
> [auto build test ERROR on linuxtv-media/master]
> [also build test ERROR on linus/master v5.7-rc3 next-20200428]
> [if your patch is applied to the wrong git tree, please drop us a note to help
> improve the system. BTW, we also suggest to use '--base' option to specify the
> base tree in git format-patch, please see https://stackoverflow.com/a/37406982]
>
> url:    https://github.com/0day-ci/linux/commits/Jacopo-Mondi/media-Register-read-only-sub-dev-devnode/20200429-062133
> base:   git://linuxtv.org/media_tree.git master
> config: arm-at91_dt_defconfig (attached as .config)
> compiler: arm-linux-gnueabi-gcc (GCC) 9.3.0
> reproduce:
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day GCC_VERSION=9.3.0 make.cross ARCH=arm
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kbuild test robot <lkp@intel.com>
>
> All errors (new ones prefixed by >>):
>
>    drivers/media/v4l2-core/v4l2-subdev.c: In function 'subdev_fh_init':
> >> drivers/media/v4l2-core/v4l2-subdev.c:28:5: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>       28 |   fh->pad = v4l2_subdev_alloc_pad_config(sd);
>          |     ^~
>    drivers/media/v4l2-core/v4l2-subdev.c:29:9: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>       29 |   if (fh->pad == NULL)
>          |         ^~
>    drivers/media/v4l2-core/v4l2-subdev.c: In function 'subdev_fh_free':
>    drivers/media/v4l2-core/v4l2-subdev.c:38:32: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>       38 |  v4l2_subdev_free_pad_config(fh->pad);
>          |                                ^~
>    drivers/media/v4l2-core/v4l2-subdev.c:39:4: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>       39 |  fh->pad = NULL;
>          |    ^~
>    In file included from include/media/v4l2-device.h:13,
>                     from drivers/media/v4l2-core/v4l2-subdev.c:20:
>    drivers/media/v4l2-core/v4l2-subdev.c: In function 'subdev_do_ioctl':
>    drivers/media/v4l2-core/v4l2-subdev.c:469:54: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>      469 |   return v4l2_subdev_call(sd, pad, get_fmt, subdev_fh->pad, format);
>          |                                                      ^~
>    include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
>     1111 |        __sd, ##args); \
>          |                ^~~~
>    drivers/media/v4l2-core/v4l2-subdev.c:469:54: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>      469 |   return v4l2_subdev_call(sd, pad, get_fmt, subdev_fh->pad, format);
>          |                                                      ^~
>    include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
>     1113 |    __result = __sd->ops->o->f(__sd, ##args); \
>          |                                       ^~~~
>    drivers/media/v4l2-core/v4l2-subdev.c:480:54: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>      480 |   return v4l2_subdev_call(sd, pad, set_fmt, subdev_fh->pad, format);
>          |                                                      ^~
>    include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
>     1111 |        __sd, ##args); \
>          |                ^~~~
>    drivers/media/v4l2-core/v4l2-subdev.c:480:54: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>      480 |   return v4l2_subdev_call(sd, pad, set_fmt, subdev_fh->pad, format);
>          |                                                      ^~
>    include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
>     1113 |    __result = __sd->ops->o->f(__sd, ##args); \
>          |                                       ^~~~
>    drivers/media/v4l2-core/v4l2-subdev.c:494:37: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>      494 |    sd, pad, get_selection, subdev_fh->pad, &sel);
>          |                                     ^~
>    include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
>     1111 |        __sd, ##args); \
>          |                ^~~~
>    drivers/media/v4l2-core/v4l2-subdev.c:494:37: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>      494 |    sd, pad, get_selection, subdev_fh->pad, &sel);
>          |                                     ^~
>    include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
>     1113 |    __result = __sd->ops->o->f(__sd, ##args); \
>          |                                       ^~~~
>    drivers/media/v4l2-core/v4l2-subdev.c:516:37: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>      516 |    sd, pad, set_selection, subdev_fh->pad, &sel);
>          |                                     ^~
>    include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
>     1111 |        __sd, ##args); \
>          |                ^~~~
>    drivers/media/v4l2-core/v4l2-subdev.c:516:37: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>      516 |    sd, pad, set_selection, subdev_fh->pad, &sel);
>          |                                     ^~
>    include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
>     1113 |    __result = __sd->ops->o->f(__sd, ##args); \
>          |                                       ^~~~
>    drivers/media/v4l2-core/v4l2-subdev.c:527:61: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>      527 |   return v4l2_subdev_call(sd, pad, enum_mbus_code, subdev_fh->pad,
>          |                                                             ^~
>    include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
>     1111 |        __sd, ##args); \
>          |                ^~~~
>    drivers/media/v4l2-core/v4l2-subdev.c:527:61: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>      527 |   return v4l2_subdev_call(sd, pad, enum_mbus_code, subdev_fh->pad,
>          |                                                             ^~
>    include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
>     1113 |    __result = __sd->ops->o->f(__sd, ##args); \
>          |                                       ^~~~
>    drivers/media/v4l2-core/v4l2-subdev.c:535:62: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>      535 |   return v4l2_subdev_call(sd, pad, enum_frame_size, subdev_fh->pad,
>          |                                                              ^~
>    include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
>     1111 |        __sd, ##args); \
>          |                ^~~~
>    drivers/media/v4l2-core/v4l2-subdev.c:535:62: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>      535 |   return v4l2_subdev_call(sd, pad, enum_frame_size, subdev_fh->pad,
>          |                                                              ^~
>    include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
>     1113 |    __result = __sd->ops->o->f(__sd, ##args); \
>          |                                       ^~~~
>    drivers/media/v4l2-core/v4l2-subdev.c:560:66: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>      560 |   return v4l2_subdev_call(sd, pad, enum_frame_interval, subdev_fh->pad,
>          |                                                                  ^~
>    include/media/v4l2-subdev.h:1111:16: note: in definition of macro 'v4l2_subdev_call'
>     1111 |        __sd, ##args); \
>          |                ^~~~
>    drivers/media/v4l2-core/v4l2-subdev.c:560:66: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>      560 |   return v4l2_subdev_call(sd, pad, enum_frame_interval, subdev_fh->pad,
>          |                                                                  ^~
>    include/media/v4l2-subdev.h:1113:39: note: in definition of macro 'v4l2_subdev_call'
>     1113 |    __result = __sd->ops->o->f(__sd, ##args); \
>          |                                       ^~~~
>    drivers/media/v4l2-core/v4l2-subdev.c:569:37: error: 'struct v4l2_subdev_fh' has no member named 'pad'
>
> vim +28 drivers/media/v4l2-core/v4l2-subdev.c
>
> 2096a5dcf9704f drivers/media/video/v4l2-subdev.c     Laurent Pinchart  2009-12-09  24
> 7cd5a16b22af7d drivers/media/video/v4l2-subdev.c     Stanimir Varbanov 2010-05-21  25  static int subdev_fh_init(struct v4l2_subdev_fh *fh, struct v4l2_subdev *sd)
> 7cd5a16b22af7d drivers/media/video/v4l2-subdev.c     Stanimir Varbanov 2010-05-21  26  {
> 9b02cbb3ede89b drivers/media/v4l2-core/v4l2-subdev.c Laurent Pinchart  2015-04-24  27  	if (sd->entity.num_pads) {
> 9b02cbb3ede89b drivers/media/v4l2-core/v4l2-subdev.c Laurent Pinchart  2015-04-24 @28  		fh->pad = v4l2_subdev_alloc_pad_config(sd);
> ae184cda8d0eeb drivers/media/video/v4l2-subdev.c     Sakari Ailus      2011-10-14  29  		if (fh->pad == NULL)
> 7cd5a16b22af7d drivers/media/video/v4l2-subdev.c     Stanimir Varbanov 2010-05-21  30  			return -ENOMEM;
> 9b02cbb3ede89b drivers/media/v4l2-core/v4l2-subdev.c Laurent Pinchart  2015-04-24  31  	}
> b9e6aad3939a62 drivers/media/v4l2-core/v4l2-subdev.c Jacopo Mondi      2020-04-28  32
> 7cd5a16b22af7d drivers/media/video/v4l2-subdev.c     Stanimir Varbanov 2010-05-21  33  	return 0;
> 7cd5a16b22af7d drivers/media/video/v4l2-subdev.c     Stanimir Varbanov 2010-05-21  34  }
> 7cd5a16b22af7d drivers/media/video/v4l2-subdev.c     Stanimir Varbanov 2010-05-21  35
>
> :::::: The code at line 28 was first introduced by commit
> :::::: 9b02cbb3ede89b5cd84bbe4ef493bd130d76b070 [media] v4l: subdev: Add pad config allocator and init
>
> :::::: TO: Laurent Pinchart <laurent.pinchart@linaro.org>
> :::::: CC: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

Re: [PATCH v5 5/6] v4l2-subdev: add VIDIOC_SUBDEV_QUERYCAP ioctl

[Jacopo Mondi]

Hi Sakari,

On Wed, Apr 29, 2020 at 12:28:58AM +0300, Sakari Ailus wrote:
> Hi Jacopo,
>
> On Tue, Apr 28, 2020 at 11:06:08PM +0200, Jacopo Mondi wrote:
> > From: Hans Verkuil <hans.verkuil@cisco.com>
> >
> > While normal video/radio/vbi/swradio nodes have a proper QUERYCAP ioctl
> > that apps can call to determine that it is indeed a V4L2 device, there
> > is currently no equivalent for v4l-subdev nodes. Adding this ioctl will
> > solve that, and it will allow utilities like v4l2-compliance to be used
> > with these devices as well.
> >
> > SUBDEV_QUERYCAP currently returns the version and subdev_caps of the
> > subdevice. Define as the initial set of subdev_caps the read-only or
> > read/write flags, to signal to userspace which set of IOCTLs are
> > available on the subdevice.
> >
> > Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
> > Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
> > ---
> >  drivers/media/v4l2-core/v4l2-subdev.c | 12 ++++++++++++
> >  include/uapi/linux/v4l2-subdev.h      | 15 +++++++++++++++
> >  2 files changed, 27 insertions(+)
> >
> > diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> > index f3fe515b8ccb..b8c0071aa4d0 100644
> > --- a/drivers/media/v4l2-core/v4l2-subdev.c
> > +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> > @@ -15,6 +15,7 @@
> >  #include <linux/types.h>
> >  #include <linux/videodev2.h>
> >  #include <linux/export.h>
> > +#include <linux/version.h>
> >
> >  #include <media/v4l2-ctrls.h>
> >  #include <media/v4l2-device.h>
> > @@ -331,6 +332,17 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> >  	int rval;
> >
> >  	switch (cmd) {
> > +	case VIDIOC_SUBDEV_QUERYCAP: {
> > +		struct v4l2_subdev_capability *cap = arg;
> > +
> > +		memset(cap, 0, sizeof(*cap));
> > +		cap->version = LINUX_VERSION_CODE;
> > +		cap->subdev_caps |= ro_subdev ? V4L2_SUBDEV_CAP_RO_SUBDEV
> > +					      : V4L2_SUBDEV_CAP_RW_SUBDEV;
> > +
> > +		return 0;
> > +	}
> > +
> >  	case VIDIOC_QUERYCTRL:
> >  		/*
> >  		 * TODO: this really should be folded into v4l2_queryctrl (this
> > diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
> > index 03970ce30741..89dc8f2ba6b3 100644
> > --- a/include/uapi/linux/v4l2-subdev.h
> > +++ b/include/uapi/linux/v4l2-subdev.h
> > @@ -155,9 +155,24 @@ struct v4l2_subdev_selection {
> >  	__u32 reserved[8];
> >  };
> >
> > +/**
> > + * struct v4l2_subdev_capability - subdev capabilities
> > + * @device_caps: the subdev capabilities, see V4L2_SUBDEV_CAP_*.
> > + */
> > +struct v4l2_subdev_capability {
> > +	__u32 version;
> > +	__u32 subdev_caps;
>
> How do you intend to address additional fields being added to the struct in
> the future? Something else than what's been done in V4L2 traditionally?
>

I'm not sure I get what you mean here, so I assume I don't know what
"has been done in V4L2 traditionally" and why what I have here goes
against it...

Re: [PATCH v5 5/6] v4l2-subdev: add VIDIOC_SUBDEV_QUERYCAP ioctl

[Sakari Ailus]

Hi Jacopo,

On Wed, Apr 29, 2020 at 10:09:49AM +0200, Jacopo Mondi wrote:
> Hi Sakari,
> 
> On Wed, Apr 29, 2020 at 12:28:58AM +0300, Sakari Ailus wrote:
> > Hi Jacopo,
> >
> > On Tue, Apr 28, 2020 at 11:06:08PM +0200, Jacopo Mondi wrote:
> > > From: Hans Verkuil <hans.verkuil@cisco.com>
> > >
> > > While normal video/radio/vbi/swradio nodes have a proper QUERYCAP ioctl
> > > that apps can call to determine that it is indeed a V4L2 device, there
> > > is currently no equivalent for v4l-subdev nodes. Adding this ioctl will
> > > solve that, and it will allow utilities like v4l2-compliance to be used
> > > with these devices as well.
> > >
> > > SUBDEV_QUERYCAP currently returns the version and subdev_caps of the
> > > subdevice. Define as the initial set of subdev_caps the read-only or
> > > read/write flags, to signal to userspace which set of IOCTLs are
> > > available on the subdevice.
> > >
> > > Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
> > > Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
> > > ---
> > >  drivers/media/v4l2-core/v4l2-subdev.c | 12 ++++++++++++
> > >  include/uapi/linux/v4l2-subdev.h      | 15 +++++++++++++++
> > >  2 files changed, 27 insertions(+)
> > >
> > > diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> > > index f3fe515b8ccb..b8c0071aa4d0 100644
> > > --- a/drivers/media/v4l2-core/v4l2-subdev.c
> > > +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> > > @@ -15,6 +15,7 @@
> > >  #include <linux/types.h>
> > >  #include <linux/videodev2.h>
> > >  #include <linux/export.h>
> > > +#include <linux/version.h>
> > >
> > >  #include <media/v4l2-ctrls.h>
> > >  #include <media/v4l2-device.h>
> > > @@ -331,6 +332,17 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> > >  	int rval;
> > >
> > >  	switch (cmd) {
> > > +	case VIDIOC_SUBDEV_QUERYCAP: {
> > > +		struct v4l2_subdev_capability *cap = arg;
> > > +
> > > +		memset(cap, 0, sizeof(*cap));
> > > +		cap->version = LINUX_VERSION_CODE;
> > > +		cap->subdev_caps |= ro_subdev ? V4L2_SUBDEV_CAP_RO_SUBDEV
> > > +					      : V4L2_SUBDEV_CAP_RW_SUBDEV;
> > > +
> > > +		return 0;
> > > +	}
> > > +
> > >  	case VIDIOC_QUERYCTRL:
> > >  		/*
> > >  		 * TODO: this really should be folded into v4l2_queryctrl (this
> > > diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
> > > index 03970ce30741..89dc8f2ba6b3 100644
> > > --- a/include/uapi/linux/v4l2-subdev.h
> > > +++ b/include/uapi/linux/v4l2-subdev.h
> > > @@ -155,9 +155,24 @@ struct v4l2_subdev_selection {
> > >  	__u32 reserved[8];
> > >  };
> > >
> > > +/**
> > > + * struct v4l2_subdev_capability - subdev capabilities
> > > + * @device_caps: the subdev capabilities, see V4L2_SUBDEV_CAP_*.
> > > + */
> > > +struct v4l2_subdev_capability {
> > > +	__u32 version;
> > > +	__u32 subdev_caps;
> >
> > How do you intend to address additional fields being added to the struct in
> > the future? Something else than what's been done in V4L2 traditionally?
> >
> 
> I'm not sure I get what you mean here, so I assume I don't know what
> "has been done in V4L2 traditionally" and why what I have here goes
> against it...

I can't help noticing you have no reserved fields in your IOCTL argument
struct. That has generally been the way V4L2 IOCTLs have been extended when
there's been a need to.

Media controller adopted a different approach to that recently, based on
the argument size. We've discussed doing that on V4L2 but I don't think
a decision has been made.

-- 
Regards,

Sakari Ailus

Re: [PATCH v5 4/6] media: v4l2-subdev: Assume V4L2_SUBDEV_API is selected

[Sakari Ailus]

Hi Jacopo,

On Wed, Apr 29, 2020 at 09:02:15AM +0200, Jacopo Mondi wrote:
> Hi Sakari,
> 
> On Wed, Apr 29, 2020 at 12:26:43AM +0300, Sakari Ailus wrote:
> > Hi Jacopo,
> >
> > On Tue, Apr 28, 2020 at 11:06:07PM +0200, Jacopo Mondi wrote:
> > > A sub-device device node can be registered in user space only if the
> > > CONFIG_V4L2_SUBDEV_API Kconfig option is selected.
> > >
> > > Remove checks from the v4l2-subdev file handle open/close functions and
> > > ioctl handler as they are only accessible if a device node was registered
> > > to user space in first place.
> >
> > Is there other motivation with this than clean up things a little?
> >
> 
> I had to add yet-another #if defined and I got fed up. If you don't
> have a device node registered you won't be able to access any of the
> functions where the existing #if defined() where placed.
> 
> > The change increases the binary size marginally if the Kconfig option is
> > disabled.
> >
> 
> I see. Should we instead guard the whole file handle operations and
> ioctl handler instead of having #if defined() spread inside them ? I
> assume they where there as leftover, as I'm still missing the point,
> give that, as said, without V4L2_SUBDEV_API, you can't register any
> device node to userspace..

I think that's why those #ifdefs have been originally put there --- it's
just dead code without the subdev nodes, and the compiler won't be able to
figure this out.

But it seems, later on, when people have added code that supports
sub-device nodes, no #ifdefs have been added.

I think I'd make sense to remove the current #ifdefs and add dummy ops for
everything where needed that truly depends on that Kconfig option (i.e.
sub-device nodes). Or just to remove these, as your patch does. It's not a
lot of code.

-- 
Kind regards,

Sakari Ailus

Re: [PATCH v5 4/6] media: v4l2-subdev: Assume V4L2_SUBDEV_API is selected

[Jacopo Mondi]

Hi Sakari

On Wed, Apr 29, 2020 at 11:27:37AM +0300, Sakari Ailus wrote:
> Hi Jacopo,
>
> On Wed, Apr 29, 2020 at 09:02:15AM +0200, Jacopo Mondi wrote:
> > Hi Sakari,
> >
> > On Wed, Apr 29, 2020 at 12:26:43AM +0300, Sakari Ailus wrote:
> > > Hi Jacopo,
> > >
> > > On Tue, Apr 28, 2020 at 11:06:07PM +0200, Jacopo Mondi wrote:
> > > > A sub-device device node can be registered in user space only if the
> > > > CONFIG_V4L2_SUBDEV_API Kconfig option is selected.
> > > >
> > > > Remove checks from the v4l2-subdev file handle open/close functions and
> > > > ioctl handler as they are only accessible if a device node was registered
> > > > to user space in first place.
> > >
> > > Is there other motivation with this than clean up things a little?
> > >
> >
> > I had to add yet-another #if defined and I got fed up. If you don't
> > have a device node registered you won't be able to access any of the
> > functions where the existing #if defined() where placed.
> >
> > > The change increases the binary size marginally if the Kconfig option is
> > > disabled.
> > >
> >
> > I see. Should we instead guard the whole file handle operations and
> > ioctl handler instead of having #if defined() spread inside them ? I
> > assume they where there as leftover, as I'm still missing the point,
> > give that, as said, without V4L2_SUBDEV_API, you can't register any
> > device node to userspace..
>
> I think that's why those #ifdefs have been originally put there --- it's
> just dead code without the subdev nodes, and the compiler won't be able to
> figure this out.
>
> But it seems, later on, when people have added code that supports
> sub-device nodes, no #ifdefs have been added.
>
> I think I'd make sense to remove the current #ifdefs and add dummy ops for
> everything where needed that truly depends on that Kconfig option (i.e.
> sub-device nodes). Or just to remove these, as your patch does. It's not a
> lot of code.

that's what I've done now, as soon as I've run a few compile test, I'll send
a new version.

Thanks
   j

>
> --
> Kind regards,
>
> Sakari Ailus

[PATCH v5.1] media: v4l2-subdev: Guard whole fops and ioctl hdlr

[Jacopo Mondi]

A sub-device device node can be registered in user space only if the
CONFIG_V4L2_SUBDEV_API Kconfig option is selected. Currently the
open/close file operations and the ioctl handler have some parts of their
implementations guarded by #if defined(CONFIG_V4L2_SUBDEV_API), while
they are actually not accessible without a video device node registered
to user space.

Guard the whole open, close and ioctl handler and provide stubs if the
V4L2_SUBDEV_API Kconfig option is not selected.

This slightly reduces the kernel size when the option is not selected
and simplifies the file ops and ioctl implementations.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
---
A different approach compared to v5, which was anyway buggy and not a proper
solution.

Sending out for comments, while waiting for consensus on v5 [5/6] (reserved
space in the ioctl argument vs versioning based on structure size)

Compile tested with and without V4L2_SUBDEV_API Kconfig option enabled and
with drivers that depends on it built-in or as modules.

---
 drivers/media/v4l2-core/v4l2-subdev.c | 39 +++++++++++++++++++++------
 1 file changed, 31 insertions(+), 8 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 1dc263c2ca0a..6fef52880c99 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -22,24 +22,22 @@
 #include <media/v4l2-fh.h>
 #include <media/v4l2-event.h>

+#if defined(CONFIG_V4L2_SUBDEV_API)
 static int subdev_fh_init(struct v4l2_subdev_fh *fh, struct v4l2_subdev *sd)
 {
-#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
 	if (sd->entity.num_pads) {
 		fh->pad = v4l2_subdev_alloc_pad_config(sd);
 		if (fh->pad == NULL)
 			return -ENOMEM;
 	}
-#endif
+
 	return 0;
 }

 static void subdev_fh_free(struct v4l2_subdev_fh *fh)
 {
-#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
 	v4l2_subdev_free_pad_config(fh->pad);
 	fh->pad = NULL;
-#endif
 }

 static int subdev_open(struct file *file)
@@ -111,6 +109,17 @@ static int subdev_close(struct file *file)

 	return 0;
 }
+#else /* CONFIG_V4L2_SUBDEV_API */
+static int subdev_open(struct file *file)
+{
+	return 0;
+}
+
+static int subdev_close(struct file *file)
+{
+	return 0;
+}
+#endif /* CONFIG_V4L2_SUBDEV_API */

 static inline int check_which(u32 which)
 {
@@ -324,15 +333,14 @@ const struct v4l2_subdev_ops v4l2_subdev_call_wrappers = {
 };
 EXPORT_SYMBOL(v4l2_subdev_call_wrappers);

+#if defined(CONFIG_V4L2_SUBDEV_API)
 static long subdev_do_ioctl(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 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_SUBDEV_RO_DEVNODE, &vdev->flags);
-#endif
 	int rval;

 	switch (cmd) {
@@ -466,7 +474,6 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 		return ret;
 	}

-#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
 	case VIDIOC_SUBDEV_G_FMT: {
 		struct v4l2_subdev_format *format = arg;

@@ -646,7 +653,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)

 	case VIDIOC_SUBDEV_QUERYSTD:
 		return v4l2_subdev_call(sd, video, querystd, arg);
-#endif
+
 	default:
 		return v4l2_subdev_call(sd, core, ioctl, cmd, arg);
 	}
@@ -686,6 +693,22 @@ static long subdev_compat_ioctl32(struct file *file, unsigned int cmd,
 }
 #endif

+#else /* CONFIG_V4L2_SUBDEV_API */
+static long subdev_ioctl(struct file *file, unsigned int cmd,
+	unsigned long arg)
+{
+	return 0;
+}
+
+#ifdef CONFIG_COMPAT
+static long subdev_compat_ioctl32(struct file *file, unsigned int cmd,
+	unsigned long arg)
+{
+	return 0;
+}
+#endif
+#endif /* CONFIG_V4L2_SUBDEV_API */
+
 static __poll_t subdev_poll(struct file *file, poll_table *wait)
 {
 	struct video_device *vdev = video_devdata(file);
--
2.26.1

Re: [PATCH v5.1] media: v4l2-subdev: Guard whole fops and ioctl hdlr

[Sakari Ailus]

Hi Jacopo,

Thanks for the update.

On Wed, Apr 29, 2020 at 10:58:55AM +0200, Jacopo Mondi wrote:
> A sub-device device node can be registered in user space only if the
> CONFIG_V4L2_SUBDEV_API Kconfig option is selected. Currently the
> open/close file operations and the ioctl handler have some parts of their
> implementations guarded by #if defined(CONFIG_V4L2_SUBDEV_API), while
> they are actually not accessible without a video device node registered
> to user space.
> 
> Guard the whole open, close and ioctl handler and provide stubs if the
> V4L2_SUBDEV_API Kconfig option is not selected.
> 
> This slightly reduces the kernel size when the option is not selected
> and simplifies the file ops and ioctl implementations.
> 
> Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
> ---
> A different approach compared to v5, which was anyway buggy and not a proper
> solution.
> 
> Sending out for comments, while waiting for consensus on v5 [5/6] (reserved
> space in the ioctl argument vs versioning based on structure size)
> 
> Compile tested with and without V4L2_SUBDEV_API Kconfig option enabled and
> with drivers that depends on it built-in or as modules.
> 
> ---
>  drivers/media/v4l2-core/v4l2-subdev.c | 39 +++++++++++++++++++++------
>  1 file changed, 31 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index 1dc263c2ca0a..6fef52880c99 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -22,24 +22,22 @@
>  #include <media/v4l2-fh.h>
>  #include <media/v4l2-event.h>
> 
> +#if defined(CONFIG_V4L2_SUBDEV_API)
>  static int subdev_fh_init(struct v4l2_subdev_fh *fh, struct v4l2_subdev *sd)
>  {
> -#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
>  	if (sd->entity.num_pads) {
>  		fh->pad = v4l2_subdev_alloc_pad_config(sd);
>  		if (fh->pad == NULL)
>  			return -ENOMEM;
>  	}
> -#endif
> +
>  	return 0;
>  }
> 
>  static void subdev_fh_free(struct v4l2_subdev_fh *fh)
>  {
> -#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
>  	v4l2_subdev_free_pad_config(fh->pad);
>  	fh->pad = NULL;
> -#endif
>  }
> 
>  static int subdev_open(struct file *file)
> @@ -111,6 +109,17 @@ static int subdev_close(struct file *file)
> 
>  	return 0;
>  }
> +#else /* CONFIG_V4L2_SUBDEV_API */
> +static int subdev_open(struct file *file)
> +{
> +	return 0;

Perhaps:

return -ENODEV;

And I'd use inline functions in the header.

> +}
> +
> +static int subdev_close(struct file *file)
> +{
> +	return 0;
> +}
> +#endif /* CONFIG_V4L2_SUBDEV_API */
> 
>  static inline int check_which(u32 which)
>  {
> @@ -324,15 +333,14 @@ const struct v4l2_subdev_ops v4l2_subdev_call_wrappers = {
>  };
>  EXPORT_SYMBOL(v4l2_subdev_call_wrappers);
> 
> +#if defined(CONFIG_V4L2_SUBDEV_API)
>  static long subdev_do_ioctl(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 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_SUBDEV_RO_DEVNODE, &vdev->flags);
> -#endif
>  	int rval;
> 
>  	switch (cmd) {
> @@ -466,7 +474,6 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
>  		return ret;
>  	}
> 
> -#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
>  	case VIDIOC_SUBDEV_G_FMT: {
>  		struct v4l2_subdev_format *format = arg;
> 
> @@ -646,7 +653,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> 
>  	case VIDIOC_SUBDEV_QUERYSTD:
>  		return v4l2_subdev_call(sd, video, querystd, arg);
> -#endif
> +
>  	default:
>  		return v4l2_subdev_call(sd, core, ioctl, cmd, arg);
>  	}
> @@ -686,6 +693,22 @@ static long subdev_compat_ioctl32(struct file *file, unsigned int cmd,
>  }
>  #endif
> 
> +#else /* CONFIG_V4L2_SUBDEV_API */
> +static long subdev_ioctl(struct file *file, unsigned int cmd,
> +	unsigned long arg)
> +{
> +	return 0;

return -ENOTTY;

> +}
> +
> +#ifdef CONFIG_COMPAT
> +static long subdev_compat_ioctl32(struct file *file, unsigned int cmd,
> +	unsigned long arg)
> +{
> +	return 0;

Ditto.

> +}
> +#endif
> +#endif /* CONFIG_V4L2_SUBDEV_API */
> +
>  static __poll_t subdev_poll(struct file *file, poll_table *wait)
>  {
>  	struct video_device *vdev = video_devdata(file);

-- 
Kind regards,

Sakari Ailus

Re: [PATCH v5.1] media: v4l2-subdev: Guard whole fops and ioctl hdlr

[Jacopo Mondi]

Hi Sakari,

On Wed, Apr 29, 2020 at 12:49:49PM +0300, Sakari Ailus wrote:
> Hi Jacopo,
>
> Thanks for the update.
>
> On Wed, Apr 29, 2020 at 10:58:55AM +0200, Jacopo Mondi wrote:
> > A sub-device device node can be registered in user space only if the
> > CONFIG_V4L2_SUBDEV_API Kconfig option is selected. Currently the
> > open/close file operations and the ioctl handler have some parts of their
> > implementations guarded by #if defined(CONFIG_V4L2_SUBDEV_API), while
> > they are actually not accessible without a video device node registered
> > to user space.
> >
> > Guard the whole open, close and ioctl handler and provide stubs if the
> > V4L2_SUBDEV_API Kconfig option is not selected.
> >
> > This slightly reduces the kernel size when the option is not selected
> > and simplifies the file ops and ioctl implementations.
> >
> > Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
> > ---
> > A different approach compared to v5, which was anyway buggy and not a proper
> > solution.
> >
> > Sending out for comments, while waiting for consensus on v5 [5/6] (reserved
> > space in the ioctl argument vs versioning based on structure size)
> >
> > Compile tested with and without V4L2_SUBDEV_API Kconfig option enabled and
> > with drivers that depends on it built-in or as modules.
> >
> > ---
> >  drivers/media/v4l2-core/v4l2-subdev.c | 39 +++++++++++++++++++++------
> >  1 file changed, 31 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> > index 1dc263c2ca0a..6fef52880c99 100644
> > --- a/drivers/media/v4l2-core/v4l2-subdev.c
> > +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> > @@ -22,24 +22,22 @@
> >  #include <media/v4l2-fh.h>
> >  #include <media/v4l2-event.h>
> >
> > +#if defined(CONFIG_V4L2_SUBDEV_API)
> >  static int subdev_fh_init(struct v4l2_subdev_fh *fh, struct v4l2_subdev *sd)
> >  {
> > -#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
> >  	if (sd->entity.num_pads) {
> >  		fh->pad = v4l2_subdev_alloc_pad_config(sd);
> >  		if (fh->pad == NULL)
> >  			return -ENOMEM;
> >  	}
> > -#endif
> > +
> >  	return 0;
> >  }
> >
> >  static void subdev_fh_free(struct v4l2_subdev_fh *fh)
> >  {
> > -#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
> >  	v4l2_subdev_free_pad_config(fh->pad);
> >  	fh->pad = NULL;
> > -#endif
> >  }
> >
> >  static int subdev_open(struct file *file)
> > @@ -111,6 +109,17 @@ static int subdev_close(struct file *file)
> >
> >  	return 0;
> >  }
> > +#else /* CONFIG_V4L2_SUBDEV_API */
> > +static int subdev_open(struct file *file)
> > +{
> > +	return 0;
>
> Perhaps:
>
> return -ENODEV;
>
> And I'd use inline functions in the header.

There is no way this functions gets called if no device node is
registered to userspace, I think. These are only here to please the
compiler. Am I mistaken ?

Also, these function are not exported by any headers, but only the
file_operations structure that contains them is:

include/media/v4l2-subdev.h
        extern const struct v4l2_file_operations v4l2_subdev_fops;

>
> > +}
> > +
> > +static int subdev_close(struct file *file)
> > +{
> > +	return 0;
> > +}
> > +#endif /* CONFIG_V4L2_SUBDEV_API */
> >
> >  static inline int check_which(u32 which)
> >  {
> > @@ -324,15 +333,14 @@ const struct v4l2_subdev_ops v4l2_subdev_call_wrappers = {
> >  };
> >  EXPORT_SYMBOL(v4l2_subdev_call_wrappers);
> >
> > +#if defined(CONFIG_V4L2_SUBDEV_API)
> >  static long subdev_do_ioctl(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 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_SUBDEV_RO_DEVNODE, &vdev->flags);
> > -#endif
> >  	int rval;
> >
> >  	switch (cmd) {
> > @@ -466,7 +474,6 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> >  		return ret;
> >  	}
> >
> > -#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
> >  	case VIDIOC_SUBDEV_G_FMT: {
> >  		struct v4l2_subdev_format *format = arg;
> >
> > @@ -646,7 +653,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> >
> >  	case VIDIOC_SUBDEV_QUERYSTD:
> >  		return v4l2_subdev_call(sd, video, querystd, arg);
> > -#endif
> > +
> >  	default:
> >  		return v4l2_subdev_call(sd, core, ioctl, cmd, arg);
> >  	}
> > @@ -686,6 +693,22 @@ static long subdev_compat_ioctl32(struct file *file, unsigned int cmd,
> >  }
> >  #endif
> >
> > +#else /* CONFIG_V4L2_SUBDEV_API */
> > +static long subdev_ioctl(struct file *file, unsigned int cmd,
> > +	unsigned long arg)
> > +{
> > +	return 0;
>
> return -ENOTTY;
>
> > +}
> > +
> > +#ifdef CONFIG_COMPAT
> > +static long subdev_compat_ioctl32(struct file *file, unsigned int cmd,
> > +	unsigned long arg)
> > +{
> > +	return 0;
>
> Ditto.
>
> > +}
> > +#endif
> > +#endif /* CONFIG_V4L2_SUBDEV_API */
> > +
> >  static __poll_t subdev_poll(struct file *file, poll_table *wait)
> >  {
> >  	struct video_device *vdev = video_devdata(file);
>
> --
> Kind regards,
>
> Sakari Ailus

Re: [PATCH v5.1] media: v4l2-subdev: Guard whole fops and ioctl hdlr

[Sakari Ailus]

On Wed, Apr 29, 2020 at 12:16:00PM +0200, Jacopo Mondi wrote:
> Hi Sakari,
> 
> On Wed, Apr 29, 2020 at 12:49:49PM +0300, Sakari Ailus wrote:
> > Hi Jacopo,
> >
> > Thanks for the update.
> >
> > On Wed, Apr 29, 2020 at 10:58:55AM +0200, Jacopo Mondi wrote:
> > > A sub-device device node can be registered in user space only if the
> > > CONFIG_V4L2_SUBDEV_API Kconfig option is selected. Currently the
> > > open/close file operations and the ioctl handler have some parts of their
> > > implementations guarded by #if defined(CONFIG_V4L2_SUBDEV_API), while
> > > they are actually not accessible without a video device node registered
> > > to user space.
> > >
> > > Guard the whole open, close and ioctl handler and provide stubs if the
> > > V4L2_SUBDEV_API Kconfig option is not selected.
> > >
> > > This slightly reduces the kernel size when the option is not selected
> > > and simplifies the file ops and ioctl implementations.
> > >
> > > Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
> > > ---
> > > A different approach compared to v5, which was anyway buggy and not a proper
> > > solution.
> > >
> > > Sending out for comments, while waiting for consensus on v5 [5/6] (reserved
> > > space in the ioctl argument vs versioning based on structure size)
> > >
> > > Compile tested with and without V4L2_SUBDEV_API Kconfig option enabled and
> > > with drivers that depends on it built-in or as modules.
> > >
> > > ---
> > >  drivers/media/v4l2-core/v4l2-subdev.c | 39 +++++++++++++++++++++------
> > >  1 file changed, 31 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> > > index 1dc263c2ca0a..6fef52880c99 100644
> > > --- a/drivers/media/v4l2-core/v4l2-subdev.c
> > > +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> > > @@ -22,24 +22,22 @@
> > >  #include <media/v4l2-fh.h>
> > >  #include <media/v4l2-event.h>
> > >
> > > +#if defined(CONFIG_V4L2_SUBDEV_API)
> > >  static int subdev_fh_init(struct v4l2_subdev_fh *fh, struct v4l2_subdev *sd)
> > >  {
> > > -#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
> > >  	if (sd->entity.num_pads) {
> > >  		fh->pad = v4l2_subdev_alloc_pad_config(sd);
> > >  		if (fh->pad == NULL)
> > >  			return -ENOMEM;
> > >  	}
> > > -#endif
> > > +
> > >  	return 0;
> > >  }
> > >
> > >  static void subdev_fh_free(struct v4l2_subdev_fh *fh)
> > >  {
> > > -#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
> > >  	v4l2_subdev_free_pad_config(fh->pad);
> > >  	fh->pad = NULL;
> > > -#endif
> > >  }
> > >
> > >  static int subdev_open(struct file *file)
> > > @@ -111,6 +109,17 @@ static int subdev_close(struct file *file)
> > >
> > >  	return 0;
> > >  }
> > > +#else /* CONFIG_V4L2_SUBDEV_API */
> > > +static int subdev_open(struct file *file)
> > > +{
> > > +	return 0;
> >
> > Perhaps:
> >
> > return -ENODEV;
> >
> > And I'd use inline functions in the header.

Um, as they're only used here, they indeed should remain here, not in
the header. I missed that while commenting.

> 
> There is no way this functions gets called if no device node is
> registered to userspace, I think. These are only here to please the
> compiler. Am I mistaken ?

The fops struct is still there. It shouldn't be called, no, but if that
happens, then providing the right return value is helpful.

> 
> Also, these function are not exported by any headers, but only the
> file_operations structure that contains them is:
> 
> include/media/v4l2-subdev.h
>         extern const struct v4l2_file_operations v4l2_subdev_fops;

Right, agreed.

-- 
Regards,

Sakari Ailus

Re: [PATCH v5 5/6] v4l2-subdev: add VIDIOC_SUBDEV_QUERYCAP ioctl

[Hans Verkuil]

On 29/04/2020 10:18, Sakari Ailus wrote:
> Hi Jacopo,
> 
> On Wed, Apr 29, 2020 at 10:09:49AM +0200, Jacopo Mondi wrote:
>> Hi Sakari,
>>
>> On Wed, Apr 29, 2020 at 12:28:58AM +0300, Sakari Ailus wrote:
>>> Hi Jacopo,
>>>
>>> On Tue, Apr 28, 2020 at 11:06:08PM +0200, Jacopo Mondi wrote:
>>>> From: Hans Verkuil <hans.verkuil@cisco.com>
>>>>
>>>> While normal video/radio/vbi/swradio nodes have a proper QUERYCAP ioctl
>>>> that apps can call to determine that it is indeed a V4L2 device, there
>>>> is currently no equivalent for v4l-subdev nodes. Adding this ioctl will
>>>> solve that, and it will allow utilities like v4l2-compliance to be used
>>>> with these devices as well.
>>>>
>>>> SUBDEV_QUERYCAP currently returns the version and subdev_caps of the
>>>> subdevice. Define as the initial set of subdev_caps the read-only or
>>>> read/write flags, to signal to userspace which set of IOCTLs are
>>>> available on the subdevice.
>>>>
>>>> Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
>>>> Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
>>>> ---
>>>>  drivers/media/v4l2-core/v4l2-subdev.c | 12 ++++++++++++
>>>>  include/uapi/linux/v4l2-subdev.h      | 15 +++++++++++++++
>>>>  2 files changed, 27 insertions(+)
>>>>
>>>> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
>>>> index f3fe515b8ccb..b8c0071aa4d0 100644
>>>> --- a/drivers/media/v4l2-core/v4l2-subdev.c
>>>> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
>>>> @@ -15,6 +15,7 @@
>>>>  #include <linux/types.h>
>>>>  #include <linux/videodev2.h>
>>>>  #include <linux/export.h>
>>>> +#include <linux/version.h>
>>>>
>>>>  #include <media/v4l2-ctrls.h>
>>>>  #include <media/v4l2-device.h>
>>>> @@ -331,6 +332,17 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
>>>>  	int rval;
>>>>
>>>>  	switch (cmd) {
>>>> +	case VIDIOC_SUBDEV_QUERYCAP: {
>>>> +		struct v4l2_subdev_capability *cap = arg;
>>>> +
>>>> +		memset(cap, 0, sizeof(*cap));
>>>> +		cap->version = LINUX_VERSION_CODE;
>>>> +		cap->subdev_caps |= ro_subdev ? V4L2_SUBDEV_CAP_RO_SUBDEV
>>>> +					      : V4L2_SUBDEV_CAP_RW_SUBDEV;
>>>> +
>>>> +		return 0;
>>>> +	}
>>>> +
>>>>  	case VIDIOC_QUERYCTRL:
>>>>  		/*
>>>>  		 * TODO: this really should be folded into v4l2_queryctrl (this
>>>> diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
>>>> index 03970ce30741..89dc8f2ba6b3 100644
>>>> --- a/include/uapi/linux/v4l2-subdev.h
>>>> +++ b/include/uapi/linux/v4l2-subdev.h
>>>> @@ -155,9 +155,24 @@ struct v4l2_subdev_selection {
>>>>  	__u32 reserved[8];
>>>>  };
>>>>
>>>> +/**
>>>> + * struct v4l2_subdev_capability - subdev capabilities
>>>> + * @device_caps: the subdev capabilities, see V4L2_SUBDEV_CAP_*.
>>>> + */
>>>> +struct v4l2_subdev_capability {
>>>> +	__u32 version;
>>>> +	__u32 subdev_caps;
>>>
>>> How do you intend to address additional fields being added to the struct in
>>> the future? Something else than what's been done in V4L2 traditionally?
>>>
>>
>> I'm not sure I get what you mean here, so I assume I don't know what
>> "has been done in V4L2 traditionally" and why what I have here goes
>> against it...
> 
> I can't help noticing you have no reserved fields in your IOCTL argument
> struct. That has generally been the way V4L2 IOCTLs have been extended when
> there's been a need to.
> 
> Media controller adopted a different approach to that recently, based on
> the argument size. We've discussed doing that on V4L2 but I don't think
> a decision has been made.
> 

While I agree that using the argument size to do 'versioning' of the API
is a better solution, the fact is that historically we always used a 'reserved'
field. And I think we need to do that here as well. It's consistent with
the existing subdev ioctls, so I would be in favor of adding a 'u32 reserved[6];'
field.

If there are such strong feelings against it that it wouldn't be merged, then
we can always just leave it as-is. It's not worth blocking this patch just
because of that.

BTW, one thing that should be changed is the name 'subdev_caps': just name it
'capabilities'. It's a field in a struct v4l2_subdev_capability, so it is
already obvious that this is subdev specific.

Regards,

	Hans

Re: [PATCH v5 5/6] v4l2-subdev: add VIDIOC_SUBDEV_QUERYCAP ioctl

[Sakari Ailus]

Hi Hans, Jacopo,

On Wed, May 06, 2020 at 03:29:03PM +0200, Hans Verkuil wrote:
> On 29/04/2020 10:18, Sakari Ailus wrote:
> > Hi Jacopo,
> > 
> > On Wed, Apr 29, 2020 at 10:09:49AM +0200, Jacopo Mondi wrote:
> >> Hi Sakari,
> >>
> >> On Wed, Apr 29, 2020 at 12:28:58AM +0300, Sakari Ailus wrote:
> >>> Hi Jacopo,
> >>>
> >>> On Tue, Apr 28, 2020 at 11:06:08PM +0200, Jacopo Mondi wrote:
> >>>> From: Hans Verkuil <hans.verkuil@cisco.com>
> >>>>
> >>>> While normal video/radio/vbi/swradio nodes have a proper QUERYCAP ioctl
> >>>> that apps can call to determine that it is indeed a V4L2 device, there
> >>>> is currently no equivalent for v4l-subdev nodes. Adding this ioctl will
> >>>> solve that, and it will allow utilities like v4l2-compliance to be used
> >>>> with these devices as well.
> >>>>
> >>>> SUBDEV_QUERYCAP currently returns the version and subdev_caps of the
> >>>> subdevice. Define as the initial set of subdev_caps the read-only or
> >>>> read/write flags, to signal to userspace which set of IOCTLs are
> >>>> available on the subdevice.
> >>>>
> >>>> Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
> >>>> Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
> >>>> ---
> >>>>  drivers/media/v4l2-core/v4l2-subdev.c | 12 ++++++++++++
> >>>>  include/uapi/linux/v4l2-subdev.h      | 15 +++++++++++++++
> >>>>  2 files changed, 27 insertions(+)
> >>>>
> >>>> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> >>>> index f3fe515b8ccb..b8c0071aa4d0 100644
> >>>> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> >>>> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> >>>> @@ -15,6 +15,7 @@
> >>>>  #include <linux/types.h>
> >>>>  #include <linux/videodev2.h>
> >>>>  #include <linux/export.h>
> >>>> +#include <linux/version.h>
> >>>>
> >>>>  #include <media/v4l2-ctrls.h>
> >>>>  #include <media/v4l2-device.h>
> >>>> @@ -331,6 +332,17 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> >>>>  	int rval;
> >>>>
> >>>>  	switch (cmd) {
> >>>> +	case VIDIOC_SUBDEV_QUERYCAP: {
> >>>> +		struct v4l2_subdev_capability *cap = arg;
> >>>> +
> >>>> +		memset(cap, 0, sizeof(*cap));
> >>>> +		cap->version = LINUX_VERSION_CODE;
> >>>> +		cap->subdev_caps |= ro_subdev ? V4L2_SUBDEV_CAP_RO_SUBDEV
> >>>> +					      : V4L2_SUBDEV_CAP_RW_SUBDEV;
> >>>> +
> >>>> +		return 0;
> >>>> +	}
> >>>> +
> >>>>  	case VIDIOC_QUERYCTRL:
> >>>>  		/*
> >>>>  		 * TODO: this really should be folded into v4l2_queryctrl (this
> >>>> diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
> >>>> index 03970ce30741..89dc8f2ba6b3 100644
> >>>> --- a/include/uapi/linux/v4l2-subdev.h
> >>>> +++ b/include/uapi/linux/v4l2-subdev.h
> >>>> @@ -155,9 +155,24 @@ struct v4l2_subdev_selection {
> >>>>  	__u32 reserved[8];
> >>>>  };
> >>>>
> >>>> +/**
> >>>> + * struct v4l2_subdev_capability - subdev capabilities
> >>>> + * @device_caps: the subdev capabilities, see V4L2_SUBDEV_CAP_*.
> >>>> + */
> >>>> +struct v4l2_subdev_capability {
> >>>> +	__u32 version;
> >>>> +	__u32 subdev_caps;
> >>>
> >>> How do you intend to address additional fields being added to the struct in
> >>> the future? Something else than what's been done in V4L2 traditionally?
> >>>
> >>
> >> I'm not sure I get what you mean here, so I assume I don't know what
> >> "has been done in V4L2 traditionally" and why what I have here goes
> >> against it...
> > 
> > I can't help noticing you have no reserved fields in your IOCTL argument
> > struct. That has generally been the way V4L2 IOCTLs have been extended when
> > there's been a need to.
> > 
> > Media controller adopted a different approach to that recently, based on
> > the argument size. We've discussed doing that on V4L2 but I don't think
> > a decision has been made.
> > 
> 
> While I agree that using the argument size to do 'versioning' of the API
> is a better solution, the fact is that historically we always used a 'reserved'
> field. And I think we need to do that here as well. It's consistent with
> the existing subdev ioctls, so I would be in favor of adding a 'u32 reserved[6];'
> field.

Agreed. Could be even 14, in practice it matters little performance-wise.

> 
> If there are such strong feelings against it that it wouldn't be merged, then
> we can always just leave it as-is. It's not worth blocking this patch just
> because of that.

I'm not (strongly) pushing either here; just that we need to make a
decision. I'm in favour of the reserved field for the same reason. I was
just wondering whether it was intentional. :-)

> 
> BTW, one thing that should be changed is the name 'subdev_caps': just name it
> 'capabilities'. It's a field in a struct v4l2_subdev_capability, so it is
> already obvious that this is subdev specific.

-- 
Regards,

Sakari Ailus

Re: [PATCH v5 5/6] v4l2-subdev: add VIDIOC_SUBDEV_QUERYCAP ioctl

[Hans Verkuil]

On 06/05/2020 20:34, Sakari Ailus wrote:
> Hi Hans, Jacopo,
> 
> On Wed, May 06, 2020 at 03:29:03PM +0200, Hans Verkuil wrote:
>> On 29/04/2020 10:18, Sakari Ailus wrote:
>>> Hi Jacopo,
>>>
>>> On Wed, Apr 29, 2020 at 10:09:49AM +0200, Jacopo Mondi wrote:
>>>> Hi Sakari,
>>>>
>>>> On Wed, Apr 29, 2020 at 12:28:58AM +0300, Sakari Ailus wrote:
>>>>> Hi Jacopo,
>>>>>
>>>>> On Tue, Apr 28, 2020 at 11:06:08PM +0200, Jacopo Mondi wrote:
>>>>>> From: Hans Verkuil <hans.verkuil@cisco.com>
>>>>>>
>>>>>> While normal video/radio/vbi/swradio nodes have a proper QUERYCAP ioctl
>>>>>> that apps can call to determine that it is indeed a V4L2 device, there
>>>>>> is currently no equivalent for v4l-subdev nodes. Adding this ioctl will
>>>>>> solve that, and it will allow utilities like v4l2-compliance to be used
>>>>>> with these devices as well.
>>>>>>
>>>>>> SUBDEV_QUERYCAP currently returns the version and subdev_caps of the
>>>>>> subdevice. Define as the initial set of subdev_caps the read-only or
>>>>>> read/write flags, to signal to userspace which set of IOCTLs are
>>>>>> available on the subdevice.
>>>>>>
>>>>>> Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
>>>>>> Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
>>>>>> ---
>>>>>>  drivers/media/v4l2-core/v4l2-subdev.c | 12 ++++++++++++
>>>>>>  include/uapi/linux/v4l2-subdev.h      | 15 +++++++++++++++
>>>>>>  2 files changed, 27 insertions(+)
>>>>>>
>>>>>> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
>>>>>> index f3fe515b8ccb..b8c0071aa4d0 100644
>>>>>> --- a/drivers/media/v4l2-core/v4l2-subdev.c
>>>>>> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
>>>>>> @@ -15,6 +15,7 @@
>>>>>>  #include <linux/types.h>
>>>>>>  #include <linux/videodev2.h>
>>>>>>  #include <linux/export.h>
>>>>>> +#include <linux/version.h>
>>>>>>
>>>>>>  #include <media/v4l2-ctrls.h>
>>>>>>  #include <media/v4l2-device.h>
>>>>>> @@ -331,6 +332,17 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
>>>>>>  	int rval;
>>>>>>
>>>>>>  	switch (cmd) {
>>>>>> +	case VIDIOC_SUBDEV_QUERYCAP: {
>>>>>> +		struct v4l2_subdev_capability *cap = arg;
>>>>>> +
>>>>>> +		memset(cap, 0, sizeof(*cap));
>>>>>> +		cap->version = LINUX_VERSION_CODE;
>>>>>> +		cap->subdev_caps |= ro_subdev ? V4L2_SUBDEV_CAP_RO_SUBDEV
>>>>>> +					      : V4L2_SUBDEV_CAP_RW_SUBDEV;
>>>>>> +
>>>>>> +		return 0;
>>>>>> +	}
>>>>>> +
>>>>>>  	case VIDIOC_QUERYCTRL:
>>>>>>  		/*
>>>>>>  		 * TODO: this really should be folded into v4l2_queryctrl (this
>>>>>> diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
>>>>>> index 03970ce30741..89dc8f2ba6b3 100644
>>>>>> --- a/include/uapi/linux/v4l2-subdev.h
>>>>>> +++ b/include/uapi/linux/v4l2-subdev.h
>>>>>> @@ -155,9 +155,24 @@ struct v4l2_subdev_selection {
>>>>>>  	__u32 reserved[8];
>>>>>>  };
>>>>>>
>>>>>> +/**
>>>>>> + * struct v4l2_subdev_capability - subdev capabilities
>>>>>> + * @device_caps: the subdev capabilities, see V4L2_SUBDEV_CAP_*.
>>>>>> + */
>>>>>> +struct v4l2_subdev_capability {
>>>>>> +	__u32 version;
>>>>>> +	__u32 subdev_caps;
>>>>>
>>>>> How do you intend to address additional fields being added to the struct in
>>>>> the future? Something else than what's been done in V4L2 traditionally?
>>>>>
>>>>
>>>> I'm not sure I get what you mean here, so I assume I don't know what
>>>> "has been done in V4L2 traditionally" and why what I have here goes
>>>> against it...
>>>
>>> I can't help noticing you have no reserved fields in your IOCTL argument
>>> struct. That has generally been the way V4L2 IOCTLs have been extended when
>>> there's been a need to.
>>>
>>> Media controller adopted a different approach to that recently, based on
>>> the argument size. We've discussed doing that on V4L2 but I don't think
>>> a decision has been made.
>>>
>>
>> While I agree that using the argument size to do 'versioning' of the API
>> is a better solution, the fact is that historically we always used a 'reserved'
>> field. And I think we need to do that here as well. It's consistent with
>> the existing subdev ioctls, so I would be in favor of adding a 'u32 reserved[6];'
>> field.
> 
> Agreed. Could be even 14, in practice it matters little performance-wise.

True. Let's make it 14.

Regards,

	Hans

> 
>>
>> If there are such strong feelings against it that it wouldn't be merged, then
>> we can always just leave it as-is. It's not worth blocking this patch just
>> because of that.
> 
> I'm not (strongly) pushing either here; just that we need to make a
> decision. I'm in favour of the reserved field for the same reason. I was
> just wondering whether it was intentional. :-)
> 
>>
>> BTW, one thing that should be changed is the name 'subdev_caps': just name it
>> 'capabilities'. It's a field in a struct v4l2_subdev_capability, so it is
>> already obvious that this is subdev specific.
>