Linux 4.6-rc6

[cris-mirror.git] / include / media / v4l2-ctrls.h

/*
    V4L2 controls support header.

    Copyright (C) 2010  Hans Verkuil <hverkuil@xs4all.nl>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifndef _V4L2_CTRLS_H
#define _V4L2_CTRLS_H

#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/videodev2.h>

/* forward references */
struct file;
struct v4l2_ctrl_handler;
struct v4l2_ctrl_helper;
struct v4l2_ctrl;
struct video_device;
struct v4l2_subdev;
struct v4l2_subscribed_event;
struct v4l2_fh;
struct poll_table_struct;

/**
 * union v4l2_ctrl_ptr - A pointer to a control value.
 * @p_s32:      Pointer to a 32-bit signed value.
 * @p_s64:      Pointer to a 64-bit signed value.
 * @p_u8:       Pointer to a 8-bit unsigned value.
 * @p_u16:      Pointer to a 16-bit unsigned value.
 * @p_u32:      Pointer to a 32-bit unsigned value.
 * @p_char:     Pointer to a string.
 * @p:          Pointer to a compound value.
 */
union v4l2_ctrl_ptr {
        s32 *p_s32;
        s64 *p_s64;
        u8 *p_u8;
        u16 *p_u16;
        u32 *p_u32;
        char *p_char;
        void *p;
};

/**
 * struct v4l2_ctrl_ops - The control operations that the driver has to provide.
 * @g_volatile_ctrl: Get a new value for this control. Generally only relevant
 *              for volatile (and usually read-only) controls such as a control
 *              that returns the current signal strength which changes
 *              continuously.
 *              If not set, then the currently cached value will be returned.
 * @try_ctrl:   Test whether the control's value is valid. Only relevant when
 *              the usual min/max/step checks are not sufficient.
 * @s_ctrl:     Actually set the new control value. s_ctrl is compulsory. The
 *              ctrl->handler->lock is held when these ops are called, so no
 *              one else can access controls owned by that handler.
 */
struct v4l2_ctrl_ops {
        int (*g_volatile_ctrl)(struct v4l2_ctrl *ctrl);
        int (*try_ctrl)(struct v4l2_ctrl *ctrl);
        int (*s_ctrl)(struct v4l2_ctrl *ctrl);
};

/**
 * struct v4l2_ctrl_type_ops - The control type operations that the driver
 *                             has to provide.
 *
 * @equal: return true if both values are equal.
 * @init: initialize the value.
 * @log: log the value.
 * @validate: validate the value. Return 0 on success and a negative value otherwise.
 */
struct v4l2_ctrl_type_ops {
        bool (*equal)(const struct v4l2_ctrl *ctrl, u32 idx,
                      union v4l2_ctrl_ptr ptr1,
                      union v4l2_ctrl_ptr ptr2);
        void (*init)(const struct v4l2_ctrl *ctrl, u32 idx,
                     union v4l2_ctrl_ptr ptr);
        void (*log)(const struct v4l2_ctrl *ctrl);
        int (*validate)(const struct v4l2_ctrl *ctrl, u32 idx,
                        union v4l2_ctrl_ptr ptr);
};

typedef void (*v4l2_ctrl_notify_fnc)(struct v4l2_ctrl *ctrl, void *priv);

/**
 * struct v4l2_ctrl - The control structure.
 * @node:       The list node.
 * @ev_subs:    The list of control event subscriptions.
 * @handler:    The handler that owns the control.
 * @cluster:    Point to start of cluster array.
 * @ncontrols:  Number of controls in cluster array.
 * @done:       Internal flag: set for each processed control.
 * @is_new:     Set when the user specified a new value for this control. It
 *              is also set when called from v4l2_ctrl_handler_setup. Drivers
 *              should never set this flag.
 * @has_changed: Set when the current value differs from the new value. Drivers
 *              should never use this flag.
 * @is_private: If set, then this control is private to its handler and it
 *              will not be added to any other handlers. Drivers can set
 *              this flag.
 * @is_auto:   If set, then this control selects whether the other cluster
 *              members are in 'automatic' mode or 'manual' mode. This is
 *              used for autogain/gain type clusters. Drivers should never
 *              set this flag directly.
 * @is_int:    If set, then this control has a simple integer value (i.e. it
 *              uses ctrl->val).
 * @is_string: If set, then this control has type V4L2_CTRL_TYPE_STRING.
 * @is_ptr:     If set, then this control is an array and/or has type >= V4L2_CTRL_COMPOUND_TYPES
 *              and/or has type V4L2_CTRL_TYPE_STRING. In other words, struct
 *              v4l2_ext_control uses field p to point to the data.
 * @is_array: If set, then this control contains an N-dimensional array.
 * @has_volatiles: If set, then one or more members of the cluster are volatile.
 *              Drivers should never touch this flag.
 * @call_notify: If set, then call the handler's notify function whenever the
 *              control's value changes.
 * @manual_mode_value: If the is_auto flag is set, then this is the value
 *              of the auto control that determines if that control is in
 *              manual mode. So if the value of the auto control equals this
 *              value, then the whole cluster is in manual mode. Drivers should
 *              never set this flag directly.
 * @ops:        The control ops.
 * @type_ops:   The control type ops.
 * @id: The control ID.
 * @name:       The control name.
 * @type:       The control type.
 * @minimum:    The control's minimum value.
 * @maximum:    The control's maximum value.
 * @default_value: The control's default value.
 * @step:       The control's step value for non-menu controls.
 * @elems:      The number of elements in the N-dimensional array.
 * @elem_size:  The size in bytes of the control.
 * @dims:       The size of each dimension.
 * @nr_of_dims:The number of dimensions in @dims.
 * @menu_skip_mask: The control's skip mask for menu controls. This makes it
 *              easy to skip menu items that are not valid. If bit X is set,
 *              then menu item X is skipped. Of course, this only works for
 *              menus with <= 32 menu items. There are no menus that come
 *              close to that number, so this is OK. Should we ever need more,
 *              then this will have to be extended to a u64 or a bit array.
 * @qmenu:      A const char * array for all menu items. Array entries that are
 *              empty strings ("") correspond to non-existing menu items (this
 *              is in addition to the menu_skip_mask above). The last entry
 *              must be NULL.
 * @flags:      The control's flags.
 * @cur:        The control's current value.
 * @val:        The control's new s32 value.
 * @priv:       The control's private pointer. For use by the driver. It is
 *              untouched by the control framework. Note that this pointer is
 *              not freed when the control is deleted. Should this be needed
 *              then a new internal bitfield can be added to tell the framework
 *              to free this pointer.
 * @p_cur:      The control's current value represented via an union with
 *              provides a standard way of accessing control types
 *              through a pointer.
 * @p_new:      The control's new value represented via an union with provides
 *              a standard way of accessing control types
 *              through a pointer.
 */
struct v4l2_ctrl {
        /* Administrative fields */
        struct list_head node;
        struct list_head ev_subs;
        struct v4l2_ctrl_handler *handler;
        struct v4l2_ctrl **cluster;
        unsigned ncontrols;
        unsigned int done:1;

        unsigned int is_new:1;
        unsigned int has_changed:1;
        unsigned int is_private:1;
        unsigned int is_auto:1;
        unsigned int is_int:1;
        unsigned int is_string:1;
        unsigned int is_ptr:1;
        unsigned int is_array:1;
        unsigned int has_volatiles:1;
        unsigned int call_notify:1;
        unsigned int manual_mode_value:8;

        const struct v4l2_ctrl_ops *ops;
        const struct v4l2_ctrl_type_ops *type_ops;
        u32 id;
        const char *name;
        enum v4l2_ctrl_type type;
        s64 minimum, maximum, default_value;
        u32 elems;
        u32 elem_size;
        u32 dims[V4L2_CTRL_MAX_DIMS];
        u32 nr_of_dims;
        union {
                u64 step;
                u64 menu_skip_mask;
        };
        union {
                const char * const *qmenu;
                const s64 *qmenu_int;
        };
        unsigned long flags;
        void *priv;
        s32 val;
        struct {
                s32 val;
        } cur;

        union v4l2_ctrl_ptr p_new;
        union v4l2_ctrl_ptr p_cur;
};

/**
 * struct v4l2_ctrl_ref - The control reference.
 * @node:       List node for the sorted list.
 * @next:       Single-link list node for the hash.
 * @ctrl:       The actual control information.
 * @helper:     Pointer to helper struct. Used internally in prepare_ext_ctrls().
 *
 * Each control handler has a list of these refs. The list_head is used to
 * keep a sorted-by-control-ID list of all controls, while the next pointer
 * is used to link the control in the hash's bucket.
 */
struct v4l2_ctrl_ref {
        struct list_head node;
        struct v4l2_ctrl_ref *next;
        struct v4l2_ctrl *ctrl;
        struct v4l2_ctrl_helper *helper;
};

/**
 * struct v4l2_ctrl_handler - The control handler keeps track of all the
 * controls: both the controls owned by the handler and those inherited
 * from other handlers.
 * @_lock:      Default for "lock".
 * @lock:       Lock to control access to this handler and its controls.
 *              May be replaced by the user right after init.
 * @ctrls:      The list of controls owned by this handler.
 * @ctrl_refs:  The list of control references.
 * @cached:     The last found control reference. It is common that the same
 *              control is needed multiple times, so this is a simple
 *              optimization.
 * @buckets:    Buckets for the hashing. Allows for quick control lookup.
 * @notify:     A notify callback that is called whenever the control changes value.
 *              Note that the handler's lock is held when the notify function
 *              is called!
 * @notify_priv: Passed as argument to the v4l2_ctrl notify callback.
 * @nr_of_buckets: Total number of buckets in the array.
 * @error:      The error code of the first failed control addition.
 */
struct v4l2_ctrl_handler {
        struct mutex _lock;
        struct mutex *lock;
        struct list_head ctrls;
        struct list_head ctrl_refs;
        struct v4l2_ctrl_ref *cached;
        struct v4l2_ctrl_ref **buckets;
        v4l2_ctrl_notify_fnc notify;
        void *notify_priv;
        u16 nr_of_buckets;
        int error;
};

/**
 * struct v4l2_ctrl_config - Control configuration structure.
 * @ops:        The control ops.
 * @type_ops:   The control type ops. Only needed for compound controls.
 * @id: The control ID.
 * @name:       The control name.
 * @type:       The control type.
 * @min:        The control's minimum value.
 * @max:        The control's maximum value.
 * @step:       The control's step value for non-menu controls.
 * @def:        The control's default value.
 * @dims:       The size of each dimension.
 * @elem_size:  The size in bytes of the control.
 * @flags:      The control's flags.
 * @menu_skip_mask: The control's skip mask for menu controls. This makes it
 *              easy to skip menu items that are not valid. If bit X is set,
 *              then menu item X is skipped. Of course, this only works for
 *              menus with <= 64 menu items. There are no menus that come
 *              close to that number, so this is OK. Should we ever need more,
 *              then this will have to be extended to a bit array.
 * @qmenu:      A const char * array for all menu items. Array entries that are
 *              empty strings ("") correspond to non-existing menu items (this
 *              is in addition to the menu_skip_mask above). The last entry
 *              must be NULL.
 * @qmenu_int:  A const s64 integer array for all menu items of the type
 *              V4L2_CTRL_TYPE_INTEGER_MENU.
 * @is_private: If set, then this control is private to its handler and it
 *              will not be added to any other handlers.
 */
struct v4l2_ctrl_config {
        const struct v4l2_ctrl_ops *ops;
        const struct v4l2_ctrl_type_ops *type_ops;
        u32 id;
        const char *name;
        enum v4l2_ctrl_type type;
        s64 min;
        s64 max;
        u64 step;
        s64 def;
        u32 dims[V4L2_CTRL_MAX_DIMS];
        u32 elem_size;
        u32 flags;
        u64 menu_skip_mask;
        const char * const *qmenu;
        const s64 *qmenu_int;
        unsigned int is_private:1;
};

/*
 * v4l2_ctrl_fill() - Fill in the control fields based on the control ID.
 *
 * This works for all standard V4L2 controls.
 * For non-standard controls it will only fill in the given arguments
 * and @name will be NULL.
 *
 * This function will overwrite the contents of @name, @type and @flags.
 * The contents of @min, @max, @step and @def may be modified depending on
 * the type.
 *
 * Do not use in drivers! It is used internally for backwards compatibility
 * control handling only. Once all drivers are converted to use the new
 * control framework this function will no longer be exported.
 */
void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
                    s64 *min, s64 *max, u64 *step, s64 *def, u32 *flags);


/**
 * v4l2_ctrl_handler_init_class() - Initialize the control handler.
 * @hdl:        The control handler.
 * @nr_of_controls_hint: A hint of how many controls this handler is
 *              expected to refer to. This is the total number, so including
 *              any inherited controls. It doesn't have to be precise, but if
 *              it is way off, then you either waste memory (too many buckets
 *              are allocated) or the control lookup becomes slower (not enough
 *              buckets are allocated, so there are more slow list lookups).
 *              It will always work, though.
 * @key:        Used by the lock validator if CONFIG_LOCKDEP is set.
 * @name:       Used by the lock validator if CONFIG_LOCKDEP is set.
 *
 * Returns an error if the buckets could not be allocated. This error will
 * also be stored in @hdl->error.
 *
 * Never use this call directly, always use the v4l2_ctrl_handler_init
 * macro that hides the @key and @name arguments.
 */
int v4l2_ctrl_handler_init_class(struct v4l2_ctrl_handler *hdl,
                                 unsigned nr_of_controls_hint,
                                 struct lock_class_key *key, const char *name);

#ifdef CONFIG_LOCKDEP
#define v4l2_ctrl_handler_init(hdl, nr_of_controls_hint)                \
(                                                                       \
        ({                                                              \
                static struct lock_class_key _key;                      \
                v4l2_ctrl_handler_init_class(hdl, nr_of_controls_hint,  \
                                        &_key,                          \
                                        KBUILD_BASENAME ":"             \
                                        __stringify(__LINE__) ":"       \
                                        "(" #hdl ")->_lock");           \
        })                                                              \
)
#else
#define v4l2_ctrl_handler_init(hdl, nr_of_controls_hint)                \
        v4l2_ctrl_handler_init_class(hdl, nr_of_controls_hint, NULL, NULL)
#endif

/**
 * v4l2_ctrl_handler_free() - Free all controls owned by the handler and free
 * the control list.
 * @hdl:        The control handler.
 *
 * Does nothing if @hdl == NULL.
 */
void v4l2_ctrl_handler_free(struct v4l2_ctrl_handler *hdl);

/**
 * v4l2_ctrl_lock() - Helper function to lock the handler
 * associated with the control.
 * @ctrl:       The control to lock.
 */
static inline void v4l2_ctrl_lock(struct v4l2_ctrl *ctrl)
{
        mutex_lock(ctrl->handler->lock);
}

/**
 * v4l2_ctrl_unlock() - Helper function to unlock the handler
 * associated with the control.
 * @ctrl:       The control to unlock.
 */
static inline void v4l2_ctrl_unlock(struct v4l2_ctrl *ctrl)
{
        mutex_unlock(ctrl->handler->lock);
}

/**
 * v4l2_ctrl_handler_setup() - Call the s_ctrl op for all controls belonging
 * to the handler to initialize the hardware to the current control values.
 * @hdl:        The control handler.
 *
 * Button controls will be skipped, as are read-only controls.
 *
 * If @hdl == NULL, then this just returns 0.
 */
int v4l2_ctrl_handler_setup(struct v4l2_ctrl_handler *hdl);

/**
 * v4l2_ctrl_handler_log_status() - Log all controls owned by the handler.
 * @hdl:        The control handler.
 * @prefix:     The prefix to use when logging the control values. If the
 *              prefix does not end with a space, then ": " will be added
 *              after the prefix. If @prefix == NULL, then no prefix will be
 *              used.
 *
 * For use with VIDIOC_LOG_STATUS.
 *
 * Does nothing if @hdl == NULL.
 */
void v4l2_ctrl_handler_log_status(struct v4l2_ctrl_handler *hdl,
                                  const char *prefix);

/**
 * v4l2_ctrl_new_custom() - Allocate and initialize a new custom V4L2
 * control.
 * @hdl:        The control handler.
 * @cfg:        The control's configuration data.
 * @priv:       The control's driver-specific private data.
 *
 * If the &v4l2_ctrl struct could not be allocated then NULL is returned
 * and @hdl->error is set to the error code (if it wasn't set already).
 */
struct v4l2_ctrl *v4l2_ctrl_new_custom(struct v4l2_ctrl_handler *hdl,
                        const struct v4l2_ctrl_config *cfg, void *priv);

/**
 * v4l2_ctrl_new_std() - Allocate and initialize a new standard V4L2 non-menu control.
 * @hdl:        The control handler.
 * @ops:        The control ops.
 * @id: The control ID.
 * @min:        The control's minimum value.
 * @max:        The control's maximum value.
 * @step:       The control's step value
 * @def:        The control's default value.
 *
 * If the &v4l2_ctrl struct could not be allocated, or the control
 * ID is not known, then NULL is returned and @hdl->error is set to the
 * appropriate error code (if it wasn't set already).
 *
 * If @id refers to a menu control, then this function will return NULL.
 *
 * Use v4l2_ctrl_new_std_menu() when adding menu controls.
 */
struct v4l2_ctrl *v4l2_ctrl_new_std(struct v4l2_ctrl_handler *hdl,
                        const struct v4l2_ctrl_ops *ops,
                        u32 id, s64 min, s64 max, u64 step, s64 def);

/**
 * v4l2_ctrl_new_std_menu() - Allocate and initialize a new standard V4L2 menu control.
 * @hdl:        The control handler.
 * @ops:        The control ops.
 * @id: The control ID.
 * @max:        The control's maximum value.
 * @mask:       The control's skip mask for menu controls. This makes it
 *              easy to skip menu items that are not valid. If bit X is set,
 *              then menu item X is skipped. Of course, this only works for
 *              menus with <= 64 menu items. There are no menus that come
 *              close to that number, so this is OK. Should we ever need more,
 *              then this will have to be extended to a bit array.
 * @def:        The control's default value.
 *
 * Same as v4l2_ctrl_new_std(), but @min is set to 0 and the @mask value
 * determines which menu items are to be skipped.
 *
 * If @id refers to a non-menu control, then this function will return NULL.
 */
struct v4l2_ctrl *v4l2_ctrl_new_std_menu(struct v4l2_ctrl_handler *hdl,
                        const struct v4l2_ctrl_ops *ops,
                        u32 id, u8 max, u64 mask, u8 def);

/**
 * v4l2_ctrl_new_std_menu_items() - Create a new standard V4L2 menu control
 * with driver specific menu.
 * @hdl:        The control handler.
 * @ops:        The control ops.
 * @id: The control ID.
 * @max:        The control's maximum value.
 * @mask:       The control's skip mask for menu controls. This makes it
 *              easy to skip menu items that are not valid. If bit X is set,
 *              then menu item X is skipped. Of course, this only works for
 *              menus with <= 64 menu items. There are no menus that come
 *              close to that number, so this is OK. Should we ever need more,
 *              then this will have to be extended to a bit array.
 * @def:        The control's default value.
 * @qmenu:      The new menu.
 *
 * Same as v4l2_ctrl_new_std_menu(), but @qmenu will be the driver specific
 * menu of this control.
 *
 */
struct v4l2_ctrl *v4l2_ctrl_new_std_menu_items(struct v4l2_ctrl_handler *hdl,
                        const struct v4l2_ctrl_ops *ops, u32 id, u8 max,
                        u64 mask, u8 def, const char * const *qmenu);

/**
 * v4l2_ctrl_new_int_menu() - Create a new standard V4L2 integer menu control.
 * @hdl:        The control handler.
 * @ops:        The control ops.
 * @id: The control ID.
 * @max:        The control's maximum value.
 * @def:        The control's default value.
 * @qmenu_int:  The control's menu entries.
 *
 * Same as v4l2_ctrl_new_std_menu(), but @mask is set to 0 and it additionaly
 * takes as an argument an array of integers determining the menu items.
 *
 * If @id refers to a non-integer-menu control, then this function will return NULL.
 */
struct v4l2_ctrl *v4l2_ctrl_new_int_menu(struct v4l2_ctrl_handler *hdl,
                        const struct v4l2_ctrl_ops *ops,
                        u32 id, u8 max, u8 def, const s64 *qmenu_int);

/**
 * v4l2_ctrl_add_handler() - Add all controls from handler @add to
 * handler @hdl.
 * @hdl:        The control handler.
 * @add:        The control handler whose controls you want to add to
 *              the @hdl control handler.
 * @filter:     This function will filter which controls should be added.
 *
 * Does nothing if either of the two handlers is a NULL pointer.
 * If @filter is NULL, then all controls are added. Otherwise only those
 * controls for which @filter returns true will be added.
 * In case of an error @hdl->error will be set to the error code (if it
 * wasn't set already).
 */
int v4l2_ctrl_add_handler(struct v4l2_ctrl_handler *hdl,
                          struct v4l2_ctrl_handler *add,
                          bool (*filter)(const struct v4l2_ctrl *ctrl));

/**
 * v4l2_ctrl_radio_filter() - Standard filter for radio controls.
 * @ctrl:       The control that is filtered.
 *
 * This will return true for any controls that are valid for radio device
 * nodes. Those are all of the V4L2_CID_AUDIO_* user controls and all FM
 * transmitter class controls.
 *
 * This function is to be used with v4l2_ctrl_add_handler().
 */
bool v4l2_ctrl_radio_filter(const struct v4l2_ctrl *ctrl);

/**
 * v4l2_ctrl_cluster() - Mark all controls in the cluster as belonging to that cluster.
 * @ncontrols:  The number of controls in this cluster.
 * @controls:   The cluster control array of size @ncontrols.
 */
void v4l2_ctrl_cluster(unsigned ncontrols, struct v4l2_ctrl **controls);


/**
 * v4l2_ctrl_auto_cluster() - Mark all controls in the cluster as belonging to
 * that cluster and set it up for autofoo/foo-type handling.
 * @ncontrols:  The number of controls in this cluster.
 * @controls:   The cluster control array of size @ncontrols. The first control
 *              must be the 'auto' control (e.g. autogain, autoexposure, etc.)
 * @manual_val: The value for the first control in the cluster that equals the
 *              manual setting.
 * @set_volatile: If true, then all controls except the first auto control will
 *              be volatile.
 *
 * Use for control groups where one control selects some automatic feature and
 * the other controls are only active whenever the automatic feature is turned
 * off (manual mode). Typical examples: autogain vs gain, auto-whitebalance vs
 * red and blue balance, etc.
 *
 * The behavior of such controls is as follows:
 *
 * When the autofoo control is set to automatic, then any manual controls
 * are set to inactive and any reads will call g_volatile_ctrl (if the control
 * was marked volatile).
 *
 * When the autofoo control is set to manual, then any manual controls will
 * be marked active, and any reads will just return the current value without
 * going through g_volatile_ctrl.
 *
 * In addition, this function will set the V4L2_CTRL_FLAG_UPDATE flag
 * on the autofoo control and V4L2_CTRL_FLAG_INACTIVE on the foo control(s)
 * if autofoo is in auto mode.
 */
void v4l2_ctrl_auto_cluster(unsigned ncontrols, struct v4l2_ctrl **controls,
                        u8 manual_val, bool set_volatile);


/**
 * v4l2_ctrl_find() - Find a control with the given ID.
 * @hdl:        The control handler.
 * @id: The control ID to find.
 *
 * If @hdl == NULL this will return NULL as well. Will lock the handler so
 * do not use from inside &v4l2_ctrl_ops.
 */
struct v4l2_ctrl *v4l2_ctrl_find(struct v4l2_ctrl_handler *hdl, u32 id);

/**
 * v4l2_ctrl_activate() - Make the control active or inactive.
 * @ctrl:       The control to (de)activate.
 * @active:     True if the control should become active.
 *
 * This sets or clears the V4L2_CTRL_FLAG_INACTIVE flag atomically.
 * Does nothing if @ctrl == NULL.
 * This will usually be called from within the s_ctrl op.
 * The V4L2_EVENT_CTRL event will be generated afterwards.
 *
 * This function assumes that the control handler is locked.
 */
void v4l2_ctrl_activate(struct v4l2_ctrl *ctrl, bool active);

/**
 * v4l2_ctrl_grab() - Mark the control as grabbed or not grabbed.
 * @ctrl:       The control to (de)activate.
 * @grabbed:    True if the control should become grabbed.
 *
 * This sets or clears the V4L2_CTRL_FLAG_GRABBED flag atomically.
 * Does nothing if @ctrl == NULL.
 * The V4L2_EVENT_CTRL event will be generated afterwards.
 * This will usually be called when starting or stopping streaming in the
 * driver.
 *
 * This function assumes that the control handler is not locked and will
 * take the lock itself.
 */
void v4l2_ctrl_grab(struct v4l2_ctrl *ctrl, bool grabbed);


/**
 *__v4l2_ctrl_modify_range() - Unlocked variant of v4l2_ctrl_modify_range()
 *
 * @ctrl:       The control to update.
 * @min:        The control's minimum value.
 * @max:        The control's maximum value.
 * @step:       The control's step value
 * @def:        The control's default value.
 *
 * Update the range of a control on the fly. This works for control types
 * INTEGER, BOOLEAN, MENU, INTEGER MENU and BITMASK. For menu controls the
 * @step value is interpreted as a menu_skip_mask.
 *
 * An error is returned if one of the range arguments is invalid for this
 * control type.
 *
 * This function assumes that the control handler is not locked and will
 * take the lock itself.
 */
int __v4l2_ctrl_modify_range(struct v4l2_ctrl *ctrl,
                             s64 min, s64 max, u64 step, s64 def);

/**
 * v4l2_ctrl_modify_range() - Update the range of a control.
 * @ctrl:       The control to update.
 * @min:        The control's minimum value.
 * @max:        The control's maximum value.
 * @step:       The control's step value
 * @def:        The control's default value.
 *
 * Update the range of a control on the fly. This works for control types
 * INTEGER, BOOLEAN, MENU, INTEGER MENU and BITMASK. For menu controls the
 * @step value is interpreted as a menu_skip_mask.
 *
 * An error is returned if one of the range arguments is invalid for this
 * control type.
 *
 * This function assumes that the control handler is not locked and will
 * take the lock itself.
 */
static inline int v4l2_ctrl_modify_range(struct v4l2_ctrl *ctrl,
                                         s64 min, s64 max, u64 step, s64 def)
{
        int rval;

        v4l2_ctrl_lock(ctrl);
        rval = __v4l2_ctrl_modify_range(ctrl, min, max, step, def);
        v4l2_ctrl_unlock(ctrl);

        return rval;
}

/**
 * v4l2_ctrl_notify() - Function to set a notify callback for a control.
 * @ctrl:       The control.
 * @notify:     The callback function.
 * @priv:       The callback private handle, passed as argument to the callback.
 *
 * This function sets a callback function for the control. If @ctrl is NULL,
 * then it will do nothing. If @notify is NULL, then the notify callback will
 * be removed.
 *
 * There can be only one notify. If another already exists, then a WARN_ON
 * will be issued and the function will do nothing.
 */
void v4l2_ctrl_notify(struct v4l2_ctrl *ctrl, v4l2_ctrl_notify_fnc notify, void *priv);

/**
 * v4l2_ctrl_get_name() - Get the name of the control
 * @id:         The control ID.
 *
 * This function returns the name of the given control ID or NULL if it isn't
 * a known control.
 */
const char *v4l2_ctrl_get_name(u32 id);

/**
 * v4l2_ctrl_get_menu() - Get the menu string array of the control
 * @id:         The control ID.
 *
 * This function returns the NULL-terminated menu string array name of the
 * given control ID or NULL if it isn't a known menu control.
 */
const char * const *v4l2_ctrl_get_menu(u32 id);

/**
 * v4l2_ctrl_get_int_menu() - Get the integer menu array of the control
 * @id:         The control ID.
 * @len:        The size of the integer array.
 *
 * This function returns the integer array of the given control ID or NULL if it
 * if it isn't a known integer menu control.
 */
const s64 *v4l2_ctrl_get_int_menu(u32 id, u32 *len);

/**
 * v4l2_ctrl_g_ctrl() - Helper function to get the control's value from within a driver.
 * @ctrl:       The control.
 *
 * This returns the control's value safely by going through the control
 * framework. This function will lock the control's handler, so it cannot be
 * used from within the &v4l2_ctrl_ops functions.
 *
 * This function is for integer type controls only.
 */
s32 v4l2_ctrl_g_ctrl(struct v4l2_ctrl *ctrl);

/**
 * __v4l2_ctrl_s_ctrl() - Unlocked variant of v4l2_ctrl_s_ctrl().
 * @ctrl:       The control.
 * @val:        The new value.
 *
 * This set the control's new value safely by going through the control
 * framework. This function will lock the control's handler, so it cannot be
 * used from within the &v4l2_ctrl_ops functions.
 *
 * This function is for integer type controls only.
 */
int __v4l2_ctrl_s_ctrl(struct v4l2_ctrl *ctrl, s32 val);

/** v4l2_ctrl_s_ctrl() - Helper function to set the control's value from within a driver.
 * @ctrl:       The control.
 * @val:        The new value.
 *
 * This set the control's new value safely by going through the control
 * framework. This function will lock the control's handler, so it cannot be
 * used from within the &v4l2_ctrl_ops functions.
 *
 * This function is for integer type controls only.
 */
static inline int v4l2_ctrl_s_ctrl(struct v4l2_ctrl *ctrl, s32 val)
{
        int rval;

        v4l2_ctrl_lock(ctrl);
        rval = __v4l2_ctrl_s_ctrl(ctrl, val);
        v4l2_ctrl_unlock(ctrl);

        return rval;
}

/**
 * v4l2_ctrl_g_ctrl_int64() - Helper function to get a 64-bit control's value
 *      from within a driver.
 * @ctrl:       The control.
 *
 * This returns the control's value safely by going through the control
 * framework. This function will lock the control's handler, so it cannot be
 * used from within the &v4l2_ctrl_ops functions.
 *
 * This function is for 64-bit integer type controls only.
 */
s64 v4l2_ctrl_g_ctrl_int64(struct v4l2_ctrl *ctrl);

/**
 * __v4l2_ctrl_s_ctrl_int64() - Unlocked variant of v4l2_ctrl_s_ctrl_int64().
 *
 * @ctrl:       The control.
 * @val:        The new value.
 *
 * This set the control's new value safely by going through the control
 * framework. This function will lock the control's handler, so it cannot be
 * used from within the &v4l2_ctrl_ops functions.
 *
 * This function is for 64-bit integer type controls only.
 */
int __v4l2_ctrl_s_ctrl_int64(struct v4l2_ctrl *ctrl, s64 val);

/** v4l2_ctrl_s_ctrl_int64() - Helper function to set a 64-bit control's value
 *      from within a driver.
 *
 * @ctrl:       The control.
 * @val:        The new value.
 *
 * This set the control's new value safely by going through the control
 * framework. This function will lock the control's handler, so it cannot be
 * used from within the &v4l2_ctrl_ops functions.
 *
 * This function is for 64-bit integer type controls only.
 */
static inline int v4l2_ctrl_s_ctrl_int64(struct v4l2_ctrl *ctrl, s64 val)
{
        int rval;

        v4l2_ctrl_lock(ctrl);
        rval = __v4l2_ctrl_s_ctrl_int64(ctrl, val);
        v4l2_ctrl_unlock(ctrl);

        return rval;
}

/** __v4l2_ctrl_s_ctrl_string() - Unlocked variant of v4l2_ctrl_s_ctrl_string().
 *
 * @ctrl:       The control.
 * @s:          The new string.
 *
 * This set the control's new string safely by going through the control
 * framework. This function will lock the control's handler, so it cannot be
 * used from within the &v4l2_ctrl_ops functions.
 *
 * This function is for string type controls only.
 */
int __v4l2_ctrl_s_ctrl_string(struct v4l2_ctrl *ctrl, const char *s);

/** v4l2_ctrl_s_ctrl_string() - Helper function to set a control's string value
 *       from within a driver.
 *
 * @ctrl:       The control.
 * @s:          The new string.
 *
 * This set the control's new string safely by going through the control
 * framework. This function will lock the control's handler, so it cannot be
 * used from within the &v4l2_ctrl_ops functions.
 *
 * This function is for string type controls only.
 */
static inline int v4l2_ctrl_s_ctrl_string(struct v4l2_ctrl *ctrl, const char *s)
{
        int rval;

        v4l2_ctrl_lock(ctrl);
        rval = __v4l2_ctrl_s_ctrl_string(ctrl, s);
        v4l2_ctrl_unlock(ctrl);

        return rval;
}

/* Internal helper functions that deal with control events. */
extern const struct v4l2_subscribed_event_ops v4l2_ctrl_sub_ev_ops;
void v4l2_ctrl_replace(struct v4l2_event *old, const struct v4l2_event *new);
void v4l2_ctrl_merge(const struct v4l2_event *old, struct v4l2_event *new);

/* Can be used as a vidioc_log_status function that just dumps all controls
   associated with the filehandle. */
int v4l2_ctrl_log_status(struct file *file, void *fh);

/* Can be used as a vidioc_subscribe_event function that just subscribes
   control events. */
int v4l2_ctrl_subscribe_event(struct v4l2_fh *fh,
                                const struct v4l2_event_subscription *sub);

/* Can be used as a poll function that just polls for control events. */
unsigned int v4l2_ctrl_poll(struct file *file, struct poll_table_struct *wait);

/* Helpers for ioctl_ops. If hdl == NULL then they will all return -EINVAL. */
int v4l2_queryctrl(struct v4l2_ctrl_handler *hdl, struct v4l2_queryctrl *qc);
int v4l2_query_ext_ctrl(struct v4l2_ctrl_handler *hdl, struct v4l2_query_ext_ctrl *qc);
int v4l2_querymenu(struct v4l2_ctrl_handler *hdl, struct v4l2_querymenu *qm);
int v4l2_g_ctrl(struct v4l2_ctrl_handler *hdl, struct v4l2_control *ctrl);
int v4l2_s_ctrl(struct v4l2_fh *fh, struct v4l2_ctrl_handler *hdl,
                                                struct v4l2_control *ctrl);
int v4l2_g_ext_ctrls(struct v4l2_ctrl_handler *hdl, struct v4l2_ext_controls *c);
int v4l2_try_ext_ctrls(struct v4l2_ctrl_handler *hdl, struct v4l2_ext_controls *c);
int v4l2_s_ext_ctrls(struct v4l2_fh *fh, struct v4l2_ctrl_handler *hdl,
                                                struct v4l2_ext_controls *c);

/* Helpers for subdevices. If the associated ctrl_handler == NULL then they
   will all return -EINVAL. */
int v4l2_subdev_queryctrl(struct v4l2_subdev *sd, struct v4l2_queryctrl *qc);
int v4l2_subdev_querymenu(struct v4l2_subdev *sd, struct v4l2_querymenu *qm);
int v4l2_subdev_g_ext_ctrls(struct v4l2_subdev *sd, struct v4l2_ext_controls *cs);
int v4l2_subdev_try_ext_ctrls(struct v4l2_subdev *sd, struct v4l2_ext_controls *cs);
int v4l2_subdev_s_ext_ctrls(struct v4l2_subdev *sd, struct v4l2_ext_controls *cs);
int v4l2_subdev_g_ctrl(struct v4l2_subdev *sd, struct v4l2_control *ctrl);
int v4l2_subdev_s_ctrl(struct v4l2_subdev *sd, struct v4l2_control *ctrl);

/* Can be used as a subscribe_event function that just subscribes control
   events. */
int v4l2_ctrl_subdev_subscribe_event(struct v4l2_subdev *sd, struct v4l2_fh *fh,
                                     struct v4l2_event_subscription *sub);

/* Log all controls owned by subdev's control handler. */
int v4l2_ctrl_subdev_log_status(struct v4l2_subdev *sd);

#endif