[media] doc-rst: document v4l2-dev.h

Add documentation for v4l2-dev.h, and put it at v4l2-framework.rst,
where struct video_device is currently documented.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

3 files changed, 320 insertions, 83 deletions

diff --git a/Documentation/media/kapi/v4l2-framework.rst b/Documentation/media/kapi/v4l2-framework.rst
index de341fc5b235..315388ef6593 100644
--- a/Documentation/media/kapi/v4l2-framework.rst
+++ b/Documentation/media/kapi/v4l2-framework.rst
@@ -699,3 +699,8 @@ methods.
 
 It is expected that once the CCF becomes available on all relevant
 architectures this API will be removed.
+
+video_device kAPI
+^^^^^^^^^^^^^^^^^
+
+.. kernel-doc:: include/media/v4l2-dev.h
diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
index 70b559d7ca80..e6da353b39bc 100644
--- a/drivers/media/v4l2-core/v4l2-dev.c
+++ b/drivers/media/v4l2-core/v4l2-dev.c
@@ -812,40 +812,6 @@ static int video_register_media_controller(struct video_device *vdev, int type)
         return 0;
 }
 
-/**
- *      __video_register_device - register video4linux devices
- *      @vdev: video device structure we want to register
- *      @type: type of device to register
- *      @nr:   which device node number (0 == /dev/video0, 1 == /dev/video1, ...
- *             -1 == first free)
- *      @warn_if_nr_in_use: warn if the desired device node number
- *             was already in use and another number was chosen instead.
- *      @owner: module that owns the video device node
- *
- *      The registration code assigns minor numbers and device node numbers
- *      based on the requested type and registers the new device node with
- *      the kernel.
- *
- *      This function assumes that struct video_device was zeroed when it
- *      was allocated and does not contain any stale date.
- *
- *      An error is returned if no free minor or device node number could be
- *      found, or if the registration of the device node failed.
- *
- *      Zero is returned on success.
- *
- *      Valid types are
- *
- *      %VFL_TYPE_GRABBER - A frame grabber
- *
- *      %VFL_TYPE_VBI - Vertical blank data (undecoded)
- *
- *      %VFL_TYPE_RADIO - A radio card
- *
- *      %VFL_TYPE_SUBDEV - A subdevice
- *
- *      %VFL_TYPE_SDR - Software Defined Radio
- */
 int __video_register_device(struct video_device *vdev, int type, int nr,
                 int warn_if_nr_in_use, struct module *owner)
 {
diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
index 25a3190308fb..5921c24565cf 100644
--- a/include/media/v4l2-dev.h
+++ b/include/media/v4l2-dev.h
@@ -47,19 +47,105 @@ struct v4l2_ctrl_handler;
 
 /* Priority helper functions */
 
+/**
+ * struct v4l2_prio_state - stores the priority states
+ *
+ * @prios: array with elements to store the array priorities
+ *
+ *
+ * .. note::
+ *    The size of @prios array matches the number of priority types defined
+ *    by :ref:`enum v4l2_priority <v4l2-priority>`.
+ */
 struct v4l2_prio_state {
         atomic_t prios[4];
 };
 
+/**
+ * v4l2_prio_init - initializes a struct v4l2_prio_state
+ *
+ * @global: pointer to &struct v4l2_prio_state
+ */
 void v4l2_prio_init(struct v4l2_prio_state *global);
+
+/**
+ * v4l2_prio_change - changes the v4l2 file handler priority
+ *
+ * @global: pointer to the &struct v4l2_prio_state of the device node.
+ * @local: pointer to the desired priority, as defined by :ref:`enum v4l2_priority <v4l2-priority>`
+ * @new: Priority type requested, as defined by :ref:`enum v4l2_priority <v4l2-priority>`.
+ *
+ * .. note::
+ *      This function should be used only by the V4L2 core.
+ */
 int v4l2_prio_change(struct v4l2_prio_state *global, enum v4l2_priority *local,
                      enum v4l2_priority new);
+
+/**
+ * v4l2_prio_open - Implements the priority logic for a file handler open
+ *
+ * @global: pointer to the &struct v4l2_prio_state of the device node.
+ * @local: pointer to the desired priority, as defined by :ref:`enum v4l2_priority <v4l2-priority>`
+ *
+ * .. note::
+ *      This function should be used only by the V4L2 core.
+ */
 void v4l2_prio_open(struct v4l2_prio_state *global, enum v4l2_priority *local);
+
+/**
+ * v4l2_prio_close - Implements the priority logic for a file handler close
+ *
+ * @global: pointer to the &struct v4l2_prio_state of the device node.
+ * @local: priority to be released, as defined by :ref:`enum v4l2_priority <v4l2-priority>`
+ *
+ * .. note::
+ *      This function should be used only by the V4L2 core.
+ */
 void v4l2_prio_close(struct v4l2_prio_state *global, enum v4l2_priority local);
+
+/**
+ * v4l2_prio_max - Return the maximum priority, as stored at the @global array.
+ *
+ * @global: pointer to the &struct v4l2_prio_state of the device node.
+ *
+ * .. note::
+ *      This function should be used only by the V4L2 core.
+ */
 enum v4l2_priority v4l2_prio_max(struct v4l2_prio_state *global);
-int v4l2_prio_check(struct v4l2_prio_state *global, enum v4l2_priority local);
 
+/**
+ * v4l2_prio_close - Implements the priority logic for a file handler close
+ *
+ * @global: pointer to the &struct v4l2_prio_state of the device node.
+ * @local: desired priority, as defined by :ref:`enum v4l2_priority <v4l2-priority>` local
+ *
+ * .. note::
+ *      This function should be used only by the V4L2 core.
+ */
+int v4l2_prio_check(struct v4l2_prio_state *global, enum v4l2_priority local);
 
+/**
+ * struct v4l2_file_operations - fs operations used by a V4L2 device
+ *
+ * @owner: pointer to struct module
+ * @read: operations needed to implement the read() syscall
+ * @write: operations needed to implement the write() syscall
+ * @poll: operations needed to implement the poll() syscall
+ * @unlocked_ioctl: operations needed to implement the ioctl() syscall
+ * @compat_ioctl32: operations needed to implement the ioctl() syscall for
+ *      the special case where the Kernel uses 64 bits instructions, but
+ *      the userspace uses 32 bits.
+ * @get_unmapped_area: called by the mmap() syscall, used when %!CONFIG_MMU
+ * @mmap: operations needed to implement the mmap() syscall
+ * @open: operations needed to implement the open() syscall
+ * @release: operations needed to implement the release() syscall
+ *
+ * .. note::
+ *
+ *      Those operations are used to implemente the fs struct file_operations
+ *      at the V4L2 drivers. The V4L2 core overrides the fs ops with some
+ *      extra logic needed by the subsystem.
+ */
 struct v4l2_file_operations {
         struct module *owner;
         ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
@@ -82,6 +168,47 @@ struct v4l2_file_operations {
  *      the common handler
  */
 
+/**
+ * struct video_device - Structure used to create and manage the V4L2 device
+ *      nodes.
+ *
+ * @entity: &struct media_entity
+ * @intf_devnode: pointer to &struct media_intf_devnode
+ * @pipe: &struct media_pipeline
+ * @fops: pointer to &struct v4l2_file_operations for the video device
+ * @device_caps: device capabilities as used in v4l2_capabilities
+ * @dev: &struct device for the video device
+ * @cdev: character device
+ * @v4l2_dev: pointer to &struct v4l2_device parent
+ * @dev_parent: pointer to &struct device parent
+ * @ctrl_handler: Control handler associated with this device node.
+ *       May be NULL.
+ * @queue: &struct vb2_queue associated with this device node. May be NULL.
+ * @prio: pointer to &struct v4l2_prio_state with device's Priority state.
+ *       If NULL, then v4l2_dev->prio will be used.
+ * @name: video device name
+ * @vfl_type: V4L device type
+ * @vfl_dir: V4L receiver, transmitter or m2m
+ * @minor: device node 'minor'. It is set to -1 if the registration failed
+ * @num: number of the video device node
+ * @flags: video device flags. Use bitops to set/clear/test flags
+ * @index: attribute to differentiate multiple indices on one physical device
+ * @fh_lock: Lock for all v4l2_fhs
+ * @fh_list: List of &struct v4l2_fh
+ * @dev_debug: Internal device debug flags, not for use by drivers
+ * @tvnorms: Supported tv norms
+ *
+ * @release: video device release() callback
+ * @ioctl_ops: pointer to &struct v4l2_ioctl_ops with ioctl callbacks
+ *
+ * @valid_ioctls: bitmap with the valid ioctls for this device
+ * @disable_locking: bitmap with the ioctls that don't require locking
+ * @lock: pointer to &struct mutex serialization lock
+ *
+ * .. note::
+ *      Only set @dev_parent if that can't be deduced from @v4l2_dev.
+ */
+
 struct video_device
 {
 #if defined(CONFIG_MEDIA_CONTROLLER)
@@ -89,59 +216,45 @@ struct video_device
         struct media_intf_devnode *intf_devnode;
         struct media_pipeline pipe;
 #endif
-        /* device ops */
         const struct v4l2_file_operations *fops;
 
-        /* device capabilities as used in v4l2_capabilities */
         u32 device_caps;
 
         /* sysfs */
-        struct device dev;              /* v4l device */
-        struct cdev *cdev;              /* character device */
+        struct device dev;
+        struct cdev *cdev;
 
-        struct v4l2_device *v4l2_dev;   /* v4l2_device parent */
-        /* Only set parent if that can't be deduced from v4l2_dev */
-        struct device *dev_parent;      /* device parent */
+        struct v4l2_device *v4l2_dev;
+        struct device *dev_parent;
 
-        /* Control handler associated with this device node. May be NULL. */
         struct v4l2_ctrl_handler *ctrl_handler;
 
-        /* vb2_queue associated with this device node. May be NULL. */
         struct vb2_queue *queue;
 
-        /* Priority state. If NULL, then v4l2_dev->prio will be used. */
         struct v4l2_prio_state *prio;
 
         /* device info */
         char name[32];
-        int vfl_type;   /* device type */
-        int vfl_dir;    /* receiver, transmitter or m2m */
-        /* 'minor' is set to -1 if the registration failed */
+        int vfl_type;
+        int vfl_dir;
         int minor;
         u16 num;
-        /* use bitops to set/clear/test flags */
         unsigned long flags;
-        /* attribute to differentiate multiple indices on one physical device */
         int index;
 
         /* V4L2 file handles */
-        spinlock_t              fh_lock; /* Lock for all v4l2_fhs */
-        struct list_head        fh_list; /* List of struct v4l2_fh */
+        spinlock_t              fh_lock;
+        struct list_head        fh_list;
 
-        /* Internal device debug flags, not for use by drivers */
         int dev_debug;
 
-        /* Video standard vars */
-        v4l2_std_id tvnorms;            /* Supported tv norms */
+        v4l2_std_id tvnorms;
 
         /* callbacks */
         void (*release)(struct video_device *vdev);
-
-        /* ioctl callbacks */
         const struct v4l2_ioctl_ops *ioctl_ops;
         DECLARE_BITMAP(valid_ioctls, BASE_VIDIOC_PRIVATE);
 
-        /* serialization lock */
         DECLARE_BITMAP(disable_locking, BASE_VIDIOC_PRIVATE);
         struct mutex *lock;
 };
@@ -151,88 +264,241 @@ struct video_device
 /* dev to video-device */
 #define to_video_device(cd) container_of(cd, struct video_device, dev)
 
+/**
+ * __video_register_device - register video4linux devices
+ *
+ * @vdev: struct video_device to register
+ * @type: type of device to register
+ * @nr:   which device node number is desired:
+ *      (0 == /dev/video0, 1 == /dev/video1, ..., -1 == first free)
+ * @warn_if_nr_in_use: warn if the desired device node number
+ *        was already in use and another number was chosen instead.
+ * @owner: module that owns the video device node
+ *
+ * The registration code assigns minor numbers and device node numbers
+ * based on the requested type and registers the new device node with
+ * the kernel.
+ *
+ * This function assumes that struct video_device was zeroed when it
+ * was allocated and does not contain any stale date.
+ *
+ * An error is returned if no free minor or device node number could be
+ * found, or if the registration of the device node failed.
+ *
+ * Returns 0 on success.
+ *
+ * Valid values for @type are:
+ *
+ *      - %VFL_TYPE_GRABBER - A frame grabber
+ *      - %VFL_TYPE_VBI - Vertical blank data (undecoded)
+ *      - %VFL_TYPE_RADIO - A radio card
+ *      - %VFL_TYPE_SUBDEV - A subdevice
+ *      - %VFL_TYPE_SDR - Software Defined Radio
+ *
+ * .. note::
+ *
+ *      This function is meant to be used only inside the V4L2 core.
+ *      Drivers should use video_register_device() or
+ *      video_register_device_no_warn().
+ */
 int __must_check __video_register_device(struct video_device *vdev, int type,
                 int nr, int warn_if_nr_in_use, struct module *owner);
 
-/* Register video devices. Note that if video_register_device fails,
-   the release() callback of the video_device structure is *not* called, so
-   the caller is responsible for freeing any data. Usually that means that
-   you call video_device_release() on failure. */
+/**
+ *  video_register_device - register video4linux devices
+ *
+ * @vdev: struct video_device to register
+ * @type: type of device to register
+ * @nr:   which device node number is desired:
+ *      (0 == /dev/video0, 1 == /dev/video1, ..., -1 == first free)
+ *
+ * Internally, it calls __video_register_device(). Please see its
+ * documentation for more details.
+ *
+ * .. note::
+ *      if video_register_device fails, the release() callback of
+ *      &struct video_device structure is *not* called, so the caller
+ *      is responsible for freeing any data. Usually that means that
+ *      you video_device_release() should be called on failure.
+ */
 static inline int __must_check video_register_device(struct video_device *vdev,
                 int type, int nr)
 {
         return __video_register_device(vdev, type, nr, 1, vdev->fops->owner);
 }
 
-/* Same as video_register_device, but no warning is issued if the desired
-   device node number was already in use. */
+/**
+ *  video_register_device_no_warn - register video4linux devices
+ *
+ * @vdev: struct video_device to register
+ * @type: type of device to register
+ * @nr:   which device node number is desired:
+ *      (0 == /dev/video0, 1 == /dev/video1, ..., -1 == first free)
+ *
+ * This function is identical to video_register_device() except that no
+ * warning is issued if the desired device node number was already in use.
+ *
+ * Internally, it calls __video_register_device(). Please see its
+ * documentation for more details.
+ *
+ * .. note::
+ *      if video_register_device fails, the release() callback of
+ *      &struct video_device structure is *not* called, so the caller
+ *      is responsible for freeing any data. Usually that means that
+ *      you video_device_release() should be called on failure.
+ */
 static inline int __must_check video_register_device_no_warn(
                 struct video_device *vdev, int type, int nr)
 {
         return __video_register_device(vdev, type, nr, 0, vdev->fops->owner);
 }
 
-/* Unregister video devices. Will do nothing if vdev == NULL or
-   video_is_registered() returns false. */
+/**
+ * video_unregister_device - Unregister video devices.
+ *
+ * @vdev: &struct video_device to register
+ *
+ * Does nothing if vdev == NULL or if video_is_registered() returns false.
+ */
 void video_unregister_device(struct video_device *vdev);
 
-/* helper functions to alloc/release struct video_device, the
-   latter can also be used for video_device->release(). */
+/**
+ * video_device_alloc - helper function to alloc &struct video_device
+ *
+ * Returns NULL if %-ENOMEM or a &struct video_device on success.
+ */
 struct video_device * __must_check video_device_alloc(void);
 
-/* this release function frees the vdev pointer */
+/**
+ * video_device_release - helper function to release &struct video_device
+ *
+ * @vdev: pointer to &struct video_device
+ *
+ * Can also be used for video_device->release().
+ */
 void video_device_release(struct video_device *vdev);
 
-/* this release function does nothing, use when the video_device is a
-   static global struct. Note that having a static video_device is
-   a dubious construction at best. */
+/**
+ * video_device_release_empty - helper function to implement the
+ *      video_device->release() callback.
+ *
+ * @vdev: pointer to &struct video_device
+ *
+ * This release function does nothing.
+ *
+ * It should be used when the video_device is a static global struct.
+ *
+ * .. note::
+ *      Having a static video_device is a dubious construction at best.
+ */
 void video_device_release_empty(struct video_device *vdev);
 
-/* returns true if cmd is a known V4L2 ioctl */
+/**
+ * v4l2_is_known_ioctl - Checks if a given cmd is a known V4L ioctl
+ *
+ * @cmd: ioctl command
+ *
+ * returns true if cmd is a known V4L2 ioctl
+ */
 bool v4l2_is_known_ioctl(unsigned int cmd);
 
-/* mark that this command shouldn't use core locking */
-static inline void v4l2_disable_ioctl_locking(struct video_device *vdev, unsigned int cmd)
+/** v4l2_disable_ioctl_locking - mark that a given command
+ *      shouldn't use core locking
+ *
+ * @vdev: pointer to &struct video_device
+ * @cmd: ioctl command
+ */
+static inline void v4l2_disable_ioctl_locking(struct video_device *vdev,
+                                              unsigned int cmd)
 {
         if (_IOC_NR(cmd) < BASE_VIDIOC_PRIVATE)
                 set_bit(_IOC_NR(cmd), vdev->disable_locking);
 }
 
-/* Mark that this command isn't implemented. This must be called before
-   video_device_register. See also the comments in determine_valid_ioctls().
-   This function allows drivers to provide just one v4l2_ioctl_ops struct, but
-   disable ioctls based on the specific card that is actually found. */
-static inline void v4l2_disable_ioctl(struct video_device *vdev, unsigned int cmd)
+/**
+ * v4l2_disable_ioctl- mark that a given command isn't implemented.
+ *      shouldn't use core locking
+ *
+ * @vdev: pointer to &struct video_device
+ * @cmd: ioctl command
+ *
+ * This function allows drivers to provide just one v4l2_ioctl_ops struct, but
+ * disable ioctls based on the specific card that is actually found.
+ *
+ * .. note::
+ *
+ *    This must be called before video_register_device.
+ *    See also the comments for determine_valid_ioctls().
+ */
+static inline void v4l2_disable_ioctl(struct video_device *vdev,
+                                      unsigned int cmd)
 {
         if (_IOC_NR(cmd) < BASE_VIDIOC_PRIVATE)
                 set_bit(_IOC_NR(cmd), vdev->valid_ioctls);
 }
 
-/* helper functions to access driver private data. */
+/**
+ * video_get_drvdata - gets private data from &struct video_device.
+ *
+ * @vdev: pointer to &struct video_device
+ *
+ * returns a pointer to the private data
+ */
 static inline void *video_get_drvdata(struct video_device *vdev)
 {
         return dev_get_drvdata(&vdev->dev);
 }
 
+/**
+ * video_set_drvdata - sets private data from &struct video_device.
+ *
+ * @vdev: pointer to &struct video_device
+ * @data: private data pointer
+ */
 static inline void video_set_drvdata(struct video_device *vdev, void *data)
 {
         dev_set_drvdata(&vdev->dev, data);
 }
 
+/**
+ * video_devdata - gets &struct video_device from struct file.
+ *
+ * @file: pointer to struct file
+ */
 struct video_device *video_devdata(struct file *file);
 
-/* Combine video_get_drvdata and video_devdata as this is
-   used very often. */
+/**
+ * video_drvdata - gets private data from &struct video_device using the
+ *      struct file.
+ *
+ * @file: pointer to struct file
+ *
+ * This is function combines both video_get_drvdata() and video_devdata()
+ * as this is used very often.
+ */
 static inline void *video_drvdata(struct file *file)
 {
         return video_get_drvdata(video_devdata(file));
 }
 
+/**
+ * video_device_node_name - returns the video device name
+ *
+ * @vdev: pointer to &struct video_device
+ *
+ * Returns the device name string
+ */
 static inline const char *video_device_node_name(struct video_device *vdev)
 {
         return dev_name(&vdev->dev);
 }
 
+/**
+ * video_is_registered - returns true if the &struct video_device is registered.
+ *
+ *
+ * @vdev: pointer to &struct video_device
+ */
 static inline int video_is_registered(struct video_device *vdev)
 {
         return test_bit(V4L2_FL_REGISTERED, &vdev->flags);