[3/4] regulator: Provide optional dummy regulator for consumers

diff --git a/drivers/regulator/Kconfig b/drivers/regulator/Kconfig
index 262f62e..d424772 100644
--- a/drivers/regulator/Kconfig
+++ b/drivers/regulator/Kconfig
@@ -27,6 +27,17 @@  config REGULATOR_DEBUG
 	help
 	  Say yes here to enable debugging support.
 
+config REGULATOR_DUMMY
+	bool "Provide a dummy regulator if regulator lookups fail"
+	help
+	  If this option is enabled then when a regulator lookup fails
+	  and the board has not specified that it has provided full
+	  constraints then the regulator core will provide an always
+	  enabled dummy regulator will be provided, allowing consumer
+	  drivers to continue.
+
+	  A warning will be generated when this substitution is done.
+
 config REGULATOR_FIXED_VOLTAGE
 	tristate "Fixed voltage regulator support"
 	help
diff --git a/drivers/regulator/Makefile b/drivers/regulator/Makefile
index b3c806c..ca2d9ab 100644
--- a/drivers/regulator/Makefile
+++ b/drivers/regulator/Makefile
@@ -9,6 +9,7 @@  obj-$(CONFIG_REGULATOR_VIRTUAL_CONSUMER) += virtual.o
 obj-$(CONFIG_REGULATOR_USERSPACE_CONSUMER) += userspace-consumer.o
 
 obj-$(CONFIG_REGULATOR_BQ24022) += bq24022.o
+obj-$(CONFIG_REGULATOR_DUMMY) += dummy.o
 obj-$(CONFIG_REGULATOR_LP3971) += lp3971.o
 obj-$(CONFIG_REGULATOR_MAX1586) += max1586.o
 obj-$(CONFIG_REGULATOR_TWL4030) += twl-regulator.o
diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 114a36d..f7feb56 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -23,6 +23,8 @@ 
 #include <linux/regulator/driver.h>
 #include <linux/regulator/machine.h>
 
+#include "dummy.h"
+
 #define REGULATOR_VERSION "0.5"
 
 static DEFINE_MUTEX(regulator_list_mutex);
@@ -1115,6 +1117,22 @@  static struct regulator *_regulator_get(struct device *dev, const char *id,
 			goto found;
 		}
 	}
+
+#ifdef CONFIG_REGULATOR_DUMMY
+	if (!devname)
+		devname = "deviceless";
+
+	/* If the board didn't flag that it was fully constrained then
+	 * substitute in a dummy regulator so consumers can continue.
+	 */
+	if (!has_full_constraints) {
+		pr_warning("%s supply %s not found, using dummy regulator\n",
+			   devname, id);
+		rdev = dummy_regulator_rdev;
+		goto found;
+	}
+#endif
+
 	mutex_unlock(&regulator_list_mutex);
 	return regulator;
 
@@ -2451,8 +2469,15 @@  EXPORT_SYMBOL_GPL(regulator_get_init_drvdata);
 
 static int __init regulator_init(void)
 {
+	int ret;
+
 	printk(KERN_INFO "regulator: core version %s\n", REGULATOR_VERSION);
-	return class_register(&regulator_class);
+
+	ret = class_register(&regulator_class);
+
+	regulator_dummy_init();
+
+	return ret;
 }
 
 /* init early to allow our consumers to complete system booting */
diff --git a/drivers/regulator/dummy.c b/drivers/regulator/dummy.c
new file mode 100644
index 0000000..c7410bd
--- /dev/null
+++ b/drivers/regulator/dummy.c
@@ -0,0 +1,66 @@ 
+/*
+ * dummy.c
+ *
+ * Copyright 2010 Wolfson Microelectronics PLC.
+ *
+ * Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
+ *
+ * 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 is useful for systems with mixed controllable and
+ * non-controllable regulators, as well as for allowing testing on
+ * systems with no controllable regulators.
+ */
+
+#include <linux/err.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/machine.h>
+
+#include "dummy.h"
+
+struct regulator_dev *dummy_regulator_rdev;
+
+static struct regulator_init_data dummy_initdata;
+
+static struct regulator_ops dummy_ops;
+
+static struct regulator_desc dummy_desc = {
+	.name = "dummy",
+	.id = -1,
+	.type = REGULATOR_VOLTAGE,
+	.owner = THIS_MODULE,
+	.ops = &dummy_ops,
+};
+
+static struct platform_device *dummy_pdev;
+
+void __init regulator_dummy_init(void)
+{
+	int ret;
+
+	dummy_pdev = platform_device_alloc("reg-dummy", -1);
+	if (!dummy_pdev) {
+		pr_err("Failed to allocate dummy regulator device\n");
+		return;
+	}
+
+	ret = platform_device_add(dummy_pdev);
+	if (ret != 0) {
+		pr_err("Failed to register dummy regulator device: %d\n", ret);
+		platform_device_put(dummy_pdev);
+		return;
+	}
+
+	dummy_regulator_rdev = regulator_register(&dummy_desc, NULL,
+						  &dummy_initdata, NULL);
+	if (IS_ERR(dummy_regulator_rdev)) {
+		ret = PTR_ERR(dummy_regulator_rdev);
+		pr_err("Failed to register regulator: %d\n", ret);
+		platform_device_unregister(dummy_pdev);
+		return;
+	}
+}
diff --git a/drivers/regulator/dummy.h b/drivers/regulator/dummy.h
new file mode 100644
index 0000000..3921c0e
--- /dev/null
+++ b/drivers/regulator/dummy.h
@@ -0,0 +1,31 @@ 
+/*
+ * dummy.h
+ *
+ * Copyright 2010 Wolfson Microelectronics PLC.
+ *
+ * Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
+ *
+ * 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 is useful for systems with mixed controllable and
+ * non-controllable regulators, as well as for allowing testing on
+ * systems with no controllable regulators.
+ */
+
+#ifndef _DUMMY_H
+#define _DUMMY_H
+
+struct regulator_dev;
+
+extern struct regulator_dev *dummy_regulator_rdev;
+
+#ifdef CONFIG_REGULATOR_DUMMY
+void __init regulator_dummy_init(void);
+#else
+static inline void regulator_dummy_init(void) { }
+#endif
+
+#endif