linux/sound/core/vmaster.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Virtual master and follower controls
 *
 *  Copyright (c) 2008 by Takashi Iwai <[email protected]>
 */

#include <linux/slab.h>
#include <linux/export.h>
#include <sound/core.h>
#include <sound/control.h>
#include <sound/tlv.h>

/*
 * a subset of information returned via ctl info callback
 */
struct link_ctl_info { … };

/*
 * link master - this contains a list of follower controls that are
 * identical types, i.e. info returns the same value type and value
 * ranges, but may have different number of counts.
 *
 * The master control is so far only mono volume/switch for simplicity.
 * The same value will be applied to all followers.
 */
struct link_master { … };

/*
 * link follower - this contains a follower control element
 *
 * It fakes the control callbacks with additional attenuation by the
 * master control.  A follower may have either one or two channels.
 */

struct link_follower { … };

static int follower_update(struct link_follower *follower)
{ … }

/* get the follower ctl info and save the initial values */
static int follower_init(struct link_follower *follower)
{ … }

/* initialize master volume */
static int master_init(struct link_master *master)
{ … }

static int follower_get_val(struct link_follower *follower,
			    struct snd_ctl_elem_value *ucontrol)
{ … }

static int follower_put_val(struct link_follower *follower,
			    struct snd_ctl_elem_value *ucontrol)
{ … }

/*
 * ctl callbacks for followers
 */
static int follower_info(struct snd_kcontrol *kcontrol,
			 struct snd_ctl_elem_info *uinfo)
{ … }

static int follower_get(struct snd_kcontrol *kcontrol,
			struct snd_ctl_elem_value *ucontrol)
{ … }

static int follower_put(struct snd_kcontrol *kcontrol,
			struct snd_ctl_elem_value *ucontrol)
{ … }

static int follower_tlv_cmd(struct snd_kcontrol *kcontrol,
			    int op_flag, unsigned int size,
			    unsigned int __user *tlv)
{ … }

static void follower_free(struct snd_kcontrol *kcontrol)
{ … }

/*
 * Add a follower control to the group with the given master control
 *
 * All followers must be the same type (returning the same information
 * via info callback).  The function doesn't check it, so it's your
 * responsibility.
 *
 * Also, some additional limitations:
 * - at most two channels
 * - logarithmic volume control (dB level), no linear volume
 * - master can only attenuate the volume, no gain
 */
int _snd_ctl_add_follower(struct snd_kcontrol *master,
			  struct snd_kcontrol *follower,
			  unsigned int flags)
{ … }
EXPORT_SYMBOL(…);

/**
 * snd_ctl_add_followers - add multiple followers to vmaster
 * @card: card instance
 * @master: the target vmaster kcontrol object
 * @list: NULL-terminated list of name strings of followers to be added
 *
 * Adds the multiple follower kcontrols with the given names.
 * Returns 0 for success or a negative error code.
 */
int snd_ctl_add_followers(struct snd_card *card, struct snd_kcontrol *master,
			  const char * const *list)
{ … }
EXPORT_SYMBOL_GPL(…);

/*
 * ctl callbacks for master controls
 */
static int master_info(struct snd_kcontrol *kcontrol,
		      struct snd_ctl_elem_info *uinfo)
{ … }

static int master_get(struct snd_kcontrol *kcontrol,
		      struct snd_ctl_elem_value *ucontrol)
{ … }

static int sync_followers(struct link_master *master, int old_val, int new_val)
{ … }

static int master_put(struct snd_kcontrol *kcontrol,
		      struct snd_ctl_elem_value *ucontrol)
{ … }

static void master_free(struct snd_kcontrol *kcontrol)
{ … }


/**
 * snd_ctl_make_virtual_master - Create a virtual master control
 * @name: name string of the control element to create
 * @tlv: optional TLV int array for dB information
 *
 * Creates a virtual master control with the given name string.
 *
 * After creating a vmaster element, you can add the follower controls
 * via snd_ctl_add_follower() or snd_ctl_add_follower_uncached().
 *
 * The optional argument @tlv can be used to specify the TLV information
 * for dB scale of the master control.  It should be a single element
 * with #SNDRV_CTL_TLVT_DB_SCALE, #SNDRV_CTL_TLV_DB_MINMAX or
 * #SNDRV_CTL_TLVT_DB_MINMAX_MUTE type, and should be the max 0dB.
 *
 * Return: The created control element, or %NULL for errors (ENOMEM).
 */
struct snd_kcontrol *snd_ctl_make_virtual_master(char *name,
						 const unsigned int *tlv)
{ … }
EXPORT_SYMBOL(…);

/**
 * snd_ctl_add_vmaster_hook - Add a hook to a vmaster control
 * @kcontrol: vmaster kctl element
 * @hook: the hook function
 * @private_data: the private_data pointer to be saved
 *
 * Adds the given hook to the vmaster control element so that it's called
 * at each time when the value is changed.
 *
 * Return: Zero.
 */
int snd_ctl_add_vmaster_hook(struct snd_kcontrol *kcontrol,
			     void (*hook)(void *private_data, int),
			     void *private_data)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * snd_ctl_sync_vmaster - Sync the vmaster followers and hook
 * @kcontrol: vmaster kctl element
 * @hook_only: sync only the hook
 *
 * Forcibly call the put callback of each follower and call the hook function
 * to synchronize with the current value of the given vmaster element.
 * NOP when NULL is passed to @kcontrol.
 */
void snd_ctl_sync_vmaster(struct snd_kcontrol *kcontrol, bool hook_only)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * snd_ctl_apply_vmaster_followers - Apply function to each vmaster follower
 * @kctl: vmaster kctl element
 * @func: function to apply
 * @arg: optional function argument
 *
 * Apply the function @func to each follower kctl of the given vmaster kctl.
 *
 * Return: 0 if successful, or a negative error code
 */
int snd_ctl_apply_vmaster_followers(struct snd_kcontrol *kctl,
				    int (*func)(struct snd_kcontrol *vfollower,
						struct snd_kcontrol *follower,
						void *arg),
				    void *arg)
{ … }
EXPORT_SYMBOL_GPL(…);