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Diffstat (limited to 'target/linux/bcm27xx/patches-5.4/950-0647-Documentation-media-Document-read-only-subdevice.patch')
| -rw-r--r-- | target/linux/bcm27xx/patches-5.4/950-0647-Documentation-media-Document-read-only-subdevice.patch | 217 |
1 files changed, 217 insertions, 0 deletions
diff --git a/target/linux/bcm27xx/patches-5.4/950-0647-Documentation-media-Document-read-only-subdevice.patch b/target/linux/bcm27xx/patches-5.4/950-0647-Documentation-media-Document-read-only-subdevice.patch new file mode 100644 index 0000000000..1983334ae1 --- /dev/null +++ b/target/linux/bcm27xx/patches-5.4/950-0647-Documentation-media-Document-read-only-subdevice.patch @@ -0,0 +1,217 @@ +From c1a630e792140b4791bad84974e31b4a1cf09b1b Mon Sep 17 00:00:00 2001 +From: Jacopo Mondi <jacopo@jmondi.org> +Date: Tue, 7 Apr 2020 17:21:56 +0200 +Subject: [PATCH] Documentation: media: Document read-only subdevice + +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> +--- + Documentation/media/kapi/v4l2-subdev.rst | 44 +++++++++++++++++++ + Documentation/media/uapi/v4l/dev-subdev.rst | 5 +++ + .../media/uapi/v4l/vidioc-g-dv-timings.rst | 6 +++ + Documentation/media/uapi/v4l/vidioc-g-std.rst | 6 +++ + .../media/uapi/v4l/vidioc-subdev-g-crop.rst | 9 ++++ + .../media/uapi/v4l/vidioc-subdev-g-fmt.rst | 8 ++++ + .../v4l/vidioc-subdev-g-frame-interval.rst | 8 ++++ + .../uapi/v4l/vidioc-subdev-g-selection.rst | 8 ++++ + 8 files changed, 94 insertions(+) + +--- a/Documentation/media/kapi/v4l2-subdev.rst ++++ b/Documentation/media/kapi/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 + ---------------------- +--- a/Documentation/media/uapi/v4l/dev-subdev.rst ++++ b/Documentation/media/uapi/v4l/dev-subdev.rst +@@ -39,6 +39,11 @@ will feature a character device node on + 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 + ======== +--- a/Documentation/media/uapi/v4l/vidioc-g-dv-timings.rst ++++ b/Documentation/media/uapi/v4l/vidioc-g-dv-timings.rst +@@ -57,6 +57,10 @@ pointer to the struct :c:type:`v4l2_dv_t + 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}| + +--- a/Documentation/media/uapi/v4l/vidioc-g-std.rst ++++ b/Documentation/media/uapi/v4l/vidioc-g-std.rst +@@ -66,6 +66,9 @@ video timings (e.g. if :ref:`VIDIOC_ENUM + 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. +--- a/Documentation/media/uapi/v4l/vidioc-subdev-g-crop.rst ++++ b/Documentation/media/uapi/v4l/vidioc-subdev-g-crop.rst +@@ -73,6 +73,11 @@ crop rectangles and stored in the sub-de + 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``. +--- a/Documentation/media/uapi/v4l/vidioc-subdev-g-fmt.rst ++++ b/Documentation/media/uapi/v4l/vidioc-subdev-g-fmt.rst +@@ -78,6 +78,11 @@ current links configuration or sub-devic + 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``. + + ============ + +--- a/Documentation/media/uapi/v4l/vidioc-subdev-g-frame-interval.rst ++++ b/Documentation/media/uapi/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. +--- a/Documentation/media/uapi/v4l/vidioc-subdev-g-selection.rst ++++ b/Documentation/media/uapi/v4l/vidioc-subdev-g-selection.rst +@@ -53,6 +53,10 @@ function of the crop API, and more, are + 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``. |