[ALSA] Add virtual master control helpers

Added helper functions to implement virtual master volume controls.
The virtual master control is a control element that has multiple
slave controls.  The value of master element is equally added to
slave elements.
The functions are written for general purpose, but it's put in the
HD-audio directory as now, since HD-audio driver is the only user.
It should be moved to the common place once after other drivers use
vmaster.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

sound/pci/hda/Makefile

@@ -2,7 +2,7 @@ snd-hda-intel-y := hda_intel.o
 # since snd-hda-intel is the only driver using hda-codec,
 # merge it into a single module although it was originally
 # designed to be individual modules
-snd-hda-intel-y += hda_codec.o
+snd-hda-intel-y += hda_codec.o vmaster.o
 snd-hda-intel-$(CONFIG_PROC_FS) += hda_proc.o
 snd-hda-intel-$(CONFIG_SND_HDA_HWDEP) += hda_hwdep.o
 snd-hda-intel-$(CONFIG_SND_HDA_GENERIC) += hda_generic.o

sound/pci/hda/hda_local.h

@@ -398,4 +398,11 @@ int snd_hda_check_amp_list_power(struct hda_codec *codec,
 				 hda_nid_t nid);
 #endif /* CONFIG_SND_HDA_POWER_SAVE */
 
+/*
+ * virtual master control
+ */
+struct snd_kcontrol *snd_ctl_make_virtual_master(char *name,
+						 const unsigned int *tlv);
+int snd_ctl_add_slave(struct snd_kcontrol *master, struct snd_kcontrol *slave);
+		      
 #endif /* __SOUND_HDA_LOCAL_H */

sound/pci/hda/vmaster.c

+/*
+ * Virtual master and slave controls
+ *
+ *  Copyright (c) 2008 by Takashi Iwai <tiwai@suse.de>
+ *
+ *  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 <sound/core.h>
+#include <sound/control.h>
+
+/*
+ * a subset of information returned via ctl info callback
+ */
+struct link_ctl_info {
+	int 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 */
+};
+
+/*
+ * 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 */
+	struct snd_kcontrol slave; /* the copy of original control entry */
+};
+
+/* get the slave ctl info and save the initial values */
+static int slave_init(struct link_slave *slave)
+{
+	struct snd_ctl_elem_info *uinfo;
+	struct snd_ctl_elem_value *uctl;
+	int err, ch;
+
+	if (slave->info.count)
+		return 0; /* already initialized */
+
+	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);
+
+	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;
+}
+
+/* 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;
+		return 0;
+	}
+	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 fucntion 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)
+{
+	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->slave = *slave;
+	memcpy(srec->slave.vd, slave->vd, slave->count * sizeof(*slave->vd));
+	srec->master = master_link;
+
+	/* 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;
+}
+
+/*
+ * 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);
+	return 1;
+}
+
+static void master_free(struct snd_kcontrol *kcontrol)
+{
+	struct link_master *master = snd_kcontrol_chip(kcontrol);
+	struct link_slave *slave;
+
+	list_for_each_entry(slave, &master->slaves, list)
+		slave->master = NULL;
+	kfree(master);
+}
+
+
+/*
+ * Create a virtual master control with the given name
+ */
+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) {
+		/* FIXME: this assumes that the max volume is 0 dB */
+		kctl->vd[0].access |= SNDRV_CTL_ELEM_ACCESS_TLV_READ;
+		kctl->tlv.p = tlv;
+	}
+	return kctl;
+}