[RFC] [Patch 1/2] Add virtual master control

[Takashi Iwai <tiwai@suse.de>]

This patch adds the virtual master control to sound core.


Takashi

diff -r 1207d46e60b3 core/Kconfig
--- a/core/Kconfig	Mon Dec 03 15:15:59 2007 +0100
+++ b/core/Kconfig	Mon Dec 03 15:46:17 2007 +0100
@@ -15,6 +15,9 @@ config SND_RAWMIDI
 config SND_RAWMIDI
 	tristate
 	depends on SND
+
+config SND_VMASTER
+	bool
 
 config SND_SEQUENCER
 	tristate "Sequencer support"
diff -r 1207d46e60b3 core/Makefile
--- a/core/Makefile	Mon Dec 03 15:15:59 2007 +0100
+++ b/core/Makefile	Mon Dec 03 15:46:17 2007 +0100
@@ -6,6 +6,7 @@ snd-y     := sound.o init.o memory.o inf
 snd-y     := sound.o init.o memory.o info.o control.o misc.o device.o
 snd-$(CONFIG_ISA_DMA_API) += isadma.o
 snd-$(CONFIG_SND_OSSEMUL) += sound_oss.o info_oss.o
+snd-$(CONFIG_SND_VMASTER) += vmaster.o
 
 snd-pcm-objs := pcm.o pcm_native.o pcm_lib.o pcm_timer.o pcm_misc.o \
 		pcm_memory.o
diff -r 1207d46e60b3 core/vmaster.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/core/vmaster.c	Mon Dec 03 15:46:17 2007 +0100
@@ -0,0 +1,379 @@
+/*
+ * Virtual master and slave controls
+ *
+ *  Copyright (c) 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; 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
+ *
+ */
+
+#include <sound/driver.h>
+#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;
+}
+
+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);
+	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;
+}
+
+EXPORT_SYMBOL(snd_ctl_make_virtual_master);
diff -r 1207d46e60b3 include/control.h
--- a/include/control.h	Mon Dec 03 15:15:59 2007 +0100
+++ b/include/control.h	Mon Dec 03 15:46:17 2007 +0100
@@ -169,4 +169,12 @@ int snd_ctl_boolean_stereo_info(struct s
 int snd_ctl_boolean_stereo_info(struct snd_kcontrol *kcontrol,
 				struct snd_ctl_elem_info *uinfo);
 
+/*
+ * 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_CONTROL_H */