path: root/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_char:	Pointer to a string.
 * @p:		Pointer to a compound value.
 */
union v4l2_ctrl_ptr {
	s32 *p_s32;
	s64 *p_s64;
	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,
		      union v4l2_ctrl_ptr ptr1,
		      union v4l2_ctrl_ptr ptr2);
	void (*init)(const struct v4l2_ctrl *ctrl,
		     union v4l2_ctrl_ptr ptr);
	void (*log)(const struct v4l2_ctrl *ctrl);
	int (*validate)(const struct v4l2_ctrl *ctrl,
			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.
  * @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.
  * @val64:	The control's new s64 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.
  */
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 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.
  * @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_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_ctrl() - Add a control from another handler to this handler.
  * @hdl:	The control handler.
  * @ctrl:	The control to add.
  *
  * It will return NULL if it was unable to add the control reference.
  * If the control already belonged to the handler, then it will do
  * nothing and just return @ctrl.
  */
struct v4l2_ctrl *v4l2_ctrl_add_ctrl(struct v4l2_ctrl_handler *hdl,
					  struct v4l2_ctrl *ctrl);

/** 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() - 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.
  */
int v4l2_ctrl_modify_range(struct v4l2_ctrl *ctrl,
			s64 min, s64 max, u64 step, s64 def);

/** 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_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_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() - 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.
  */
int v4l2_ctrl_s_ctrl(struct v4l2_ctrl *ctrl, s32 val);

/** 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() - 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.
  */
int v4l2_ctrl_s_ctrl_int64(struct v4l2_ctrl *ctrl, s64 val);

/* 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