vmaster.c

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/*
 * Virtual master and slave controls
 *
 *  Copyright (c) 2008 by Takashi Iwai <[email protected]>
 *
 *  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, version 2.
 *
 */

#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 {
    snd_ctl_elem_type_t type; /* value type */
    int count;      /* item count */
    int min_val, max_val;   /* min, max values */
};

/*
 * link master - this contains a list of slave 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 slaves.
 */
struct link_master {
    struct list_head slaves;
    struct link_ctl_info info;
    int val;        /* the master value */
    unsigned int tlv[4];
    void (*hook)(void *private_data, int);
    void *hook_private_data;
};

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

struct link_slave {
    struct list_head list;
    struct link_master *master;
    struct link_ctl_info info;
    int vals[2];        /* current values */
    unsigned int flags;
    struct snd_kcontrol *kctl; /* original kcontrol pointer */
    struct snd_kcontrol slave; /* the copy of original control entry */
};

static int slave_update(struct link_slave *slave)
{
    struct snd_ctl_elem_value *uctl;
    int err, ch;

    uctl = kmalloc(sizeof(*uctl), GFP_KERNEL);
    if (!uctl)
        return -ENOMEM;
    uctl->id = slave->slave.id;
    err = slave->slave.get(&slave->slave, uctl);
    for (ch = 0; ch < slave->info.count; ch++)
        slave->vals[ch] = uctl->value.integer.value[ch];
    kfree(uctl);
    return 0;
}

/* get the slave ctl info and save the initial values */
static int slave_init(struct link_slave *slave)
{
    struct snd_ctl_elem_info *uinfo;
    int err;

    if (slave->info.count) {
        /* already initialized */
        if (slave->flags & SND_CTL_SLAVE_NEED_UPDATE)
            return slave_update(slave);
        return 0;
    }

    uinfo = kmalloc(sizeof(*uinfo), GFP_KERNEL);
    if (!uinfo)
        return -ENOMEM;
    uinfo->id = slave->slave.id;
    err = slave->slave.info(&slave->slave, uinfo);
    if (err < 0) {
        kfree(uinfo);
        return err;
    }
    slave->info.type = uinfo->type;
    slave->info.count = uinfo->count;
    if (slave->info.count > 2  ||
        (slave->info.type != SNDRV_CTL_ELEM_TYPE_INTEGER &&
         slave->info.type != SNDRV_CTL_ELEM_TYPE_BOOLEAN)) {
        snd_printk(KERN_ERR "invalid slave element\n");
        kfree(uinfo);
        return -EINVAL;
    }
    slave->info.min_val = uinfo->value.integer.min;
    slave->info.max_val = uinfo->value.integer.max;
    kfree(uinfo);

    return slave_update(slave);
}

/* initialize master volume */
static int master_init(struct link_master *master)
{
    struct link_slave *slave;

    if (master->info.count)
        return 0; /* already initialized */

    list_for_each_entry(slave, &master->slaves, list) {
        int err = slave_init(slave);
        if (err < 0)
            return err;
        master->info = slave->info;
        master->info.count = 1; /* always mono */
        /* set full volume as default (= no attenuation) */
        master->val = master->info.max_val;
        if (master->hook)
            master->hook(master->hook_private_data, master->val);
        return 1;
    }
    return -ENOENT;
}

static int slave_get_val(struct link_slave *slave,
             struct snd_ctl_elem_value *ucontrol)
{
    int err, ch;

    err = slave_init(slave);
    if (err < 0)
        return err;
    for (ch = 0; ch < slave->info.count; ch++)
        ucontrol->value.integer.value[ch] = slave->vals[ch];
    return 0;
}

static int slave_put_val(struct link_slave *slave,
             struct snd_ctl_elem_value *ucontrol)
{
    int err, ch, vol;

    err = master_init(slave->master);
    if (err < 0)
        return err;

    switch (slave->info.type) {
    case SNDRV_CTL_ELEM_TYPE_BOOLEAN:
        for (ch = 0; ch < slave->info.count; ch++)
            ucontrol->value.integer.value[ch] &=
                !!slave->master->val;
        break;
    case SNDRV_CTL_ELEM_TYPE_INTEGER:
        for (ch = 0; ch < slave->info.count; ch++) {
            /* max master volume is supposed to be 0 dB */
            vol = ucontrol->value.integer.value[ch];
            vol += slave->master->val - slave->master->info.max_val;
            if (vol < slave->info.min_val)
                vol = slave->info.min_val;
            else if (vol > slave->info.max_val)
                vol = slave->info.max_val;
            ucontrol->value.integer.value[ch] = vol;
        }
        break;
    }
    return slave->slave.put(&slave->slave, ucontrol);
}

/*
 * ctl callbacks for slaves
 */
static int slave_info(struct snd_kcontrol *kcontrol,
              struct snd_ctl_elem_info *uinfo)
{
    struct link_slave *slave = snd_kcontrol_chip(kcontrol);
    return slave->slave.info(&slave->slave, uinfo);
}

static int slave_get(struct snd_kcontrol *kcontrol,
             struct snd_ctl_elem_value *ucontrol)
{
    struct link_slave *slave = snd_kcontrol_chip(kcontrol);
    return slave_get_val(slave, ucontrol);
}

static int slave_put(struct snd_kcontrol *kcontrol,
             struct snd_ctl_elem_value *ucontrol)
{
    struct link_slave *slave = snd_kcontrol_chip(kcontrol);
    int err, ch, changed = 0;

    err = slave_init(slave);
    if (err < 0)
        return err;
    for (ch = 0; ch < slave->info.count; ch++) {
        if (slave->vals[ch] != ucontrol->value.integer.value[ch]) {
            changed = 1;
            slave->vals[ch] = ucontrol->value.integer.value[ch];
        }
    }
    if (!changed)
        return 0;
    return slave_put_val(slave, ucontrol);
}

static int slave_tlv_cmd(struct snd_kcontrol *kcontrol,
             int op_flag, unsigned int size,
             unsigned int __user *tlv)
{
    struct link_slave *slave = snd_kcontrol_chip(kcontrol);
    /* FIXME: this assumes that the max volume is 0 dB */
    return slave->slave.tlv.c(&slave->slave, op_flag, size, tlv);
}

static void slave_free(struct snd_kcontrol *kcontrol)
{
    struct link_slave *slave = snd_kcontrol_chip(kcontrol);
    if (slave->slave.private_free)
        slave->slave.private_free(&slave->slave);
    if (slave->master)
        list_del(&slave->list);
    kfree(slave);
}

/*
 * Add a slave control to the group with the given master control
 *
 * All slaves 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_slave(struct snd_kcontrol *master, struct snd_kcontrol *slave,
               unsigned int flags)
{
    struct link_master *master_link = snd_kcontrol_chip(master);
    struct link_slave *srec;

    srec = kzalloc(sizeof(*srec) +
               slave->count * sizeof(*slave->vd), GFP_KERNEL);
    if (!srec)
        return -ENOMEM;
    srec->kctl = slave;
    srec->slave = *slave;
    memcpy(srec->slave.vd, slave->vd, slave->count * sizeof(*slave->vd));
    srec->master = master_link;
    srec->flags = flags;

    /* override callbacks */
    slave->info = slave_info;
    slave->get = slave_get;
    slave->put = slave_put;
    if (slave->vd[0].access & SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK)
        slave->tlv.c = slave_tlv_cmd;
    slave->private_data = srec;
    slave->private_free = slave_free;

    list_add_tail(&srec->list, &master_link->slaves);
    return 0;
}
EXPORT_SYMBOL(_snd_ctl_add_slave);

/*
 * ctl callbacks for master controls
 */
static int master_info(struct snd_kcontrol *kcontrol,
              struct snd_ctl_elem_info *uinfo)
{
    struct link_master *master = snd_kcontrol_chip(kcontrol);
    int ret;

    ret = master_init(master);
    if (ret < 0)
        return ret;
    uinfo->type = master->info.type;
    uinfo->count = master->info.count;
    uinfo->value.integer.min = master->info.min_val;
    uinfo->value.integer.max = master->info.max_val;
    return 0;
}

static int master_get(struct snd_kcontrol *kcontrol,
              struct snd_ctl_elem_value *ucontrol)
{
    struct link_master *master = snd_kcontrol_chip(kcontrol);
    int err = master_init(master);
    if (err < 0)
        return err;
    ucontrol->value.integer.value[0] = master->val;
    return 0;
}

static int master_put(struct snd_kcontrol *kcontrol,
              struct snd_ctl_elem_value *ucontrol)
{
    struct link_master *master = snd_kcontrol_chip(kcontrol);
    struct link_slave *slave;
    struct snd_ctl_elem_value *uval;
    int err, old_val;

    err = master_init(master);
    if (err < 0)
        return err;
    old_val = master->val;
    if (ucontrol->value.integer.value[0] == old_val)
        return 0;

    uval = kmalloc(sizeof(*uval), GFP_KERNEL);
    if (!uval)
        return -ENOMEM;
    list_for_each_entry(slave, &master->slaves, list) {
        master->val = old_val;
        uval->id = slave->slave.id;
        slave_get_val(slave, uval);
        master->val = ucontrol->value.integer.value[0];
        slave_put_val(slave, uval);
    }
    kfree(uval);
    if (master->hook && !err)
        master->hook(master->hook_private_data, master->val);
    return 1;
}

static void master_free(struct snd_kcontrol *kcontrol)
{
    struct link_master *master = snd_kcontrol_chip(kcontrol);
    struct link_slave *slave, *n;

    /* free all slave links and retore the original slave kctls */
    list_for_each_entry_safe(slave, n, &master->slaves, list) {
        struct snd_kcontrol *sctl = slave->kctl;
        struct list_head olist = sctl->list;
        memcpy(sctl, &slave->slave, sizeof(*sctl));
        memcpy(sctl->vd, slave->slave.vd,
               sctl->count * sizeof(*sctl->vd));
        sctl->list = olist; /* keep the current linked-list */
        kfree(slave);
    }
    kfree(master);
}


struct snd_kcontrol *snd_ctl_make_virtual_master(char *name,
                         const unsigned int *tlv)
{
    struct link_master *master;
    struct snd_kcontrol *kctl;
    struct snd_kcontrol_new knew;

    memset(&knew, 0, sizeof(knew));
    knew.iface = SNDRV_CTL_ELEM_IFACE_MIXER;
    knew.name = name;
    knew.info = master_info;

    master = kzalloc(sizeof(*master), GFP_KERNEL);
    if (!master)
        return NULL;
    INIT_LIST_HEAD(&master->slaves);

    kctl = snd_ctl_new1(&knew, master);
    if (!kctl) {
        kfree(master);
        return NULL;
    }
    /* override some callbacks */
    kctl->info = master_info;
    kctl->get = master_get;
    kctl->put = master_put;
    kctl->private_free = master_free;

    /* additional (constant) TLV read */
    if (tlv &&
        (tlv[0] == SNDRV_CTL_TLVT_DB_SCALE ||
         tlv[0] == SNDRV_CTL_TLVT_DB_MINMAX ||
         tlv[0] == SNDRV_CTL_TLVT_DB_MINMAX_MUTE)) {
        kctl->vd[0].access |= SNDRV_CTL_ELEM_ACCESS_TLV_READ;
        memcpy(master->tlv, tlv, sizeof(master->tlv));
        kctl->tlv.p = master->tlv;
    }

    return kctl;
}
EXPORT_SYMBOL(snd_ctl_make_virtual_master);

int snd_ctl_add_vmaster_hook(struct snd_kcontrol *kcontrol,
                 void (*hook)(void *private_data, int),
                 void *private_data)
{
    struct link_master *master = snd_kcontrol_chip(kcontrol);
    master->hook = hook;
    master->hook_private_data = private_data;
    return 0;
}
EXPORT_SYMBOL_GPL(snd_ctl_add_vmaster_hook);

void snd_ctl_sync_vmaster_hook(struct snd_kcontrol *kcontrol)
{
    struct link_master *master;
    if (!kcontrol)
        return;
    master = snd_kcontrol_chip(kcontrol);
    if (master->hook)
        master->hook(master->hook_private_data, master->val);
}
EXPORT_SYMBOL_GPL(snd_ctl_sync_vmaster_hook);