regulator: Provide optional dummy regulator for consumers

In order to ease transitions with drivers are boards start using regulators
provide an option to cause all regulator_get() calls to succeed, with a
dummy always on regulator being supplied where one has not been configured.
A warning is printed whenever the dummy regulator is used to aid system
development.

This regulator does not implement any regulator operations but will allow
simple consumers which only do enable() and disable() calls to run. It
is kept separate from the fixed voltage regulator to avoid Kconfig
confusion on the part of users when it is extended to allow boards to
explicitly use the dummy regulator to simplify cases where the majority
of supplies are from fixed regulators without software control.

This option is currently only effective for systems which do not specify
full constriants. If required an override could also be provided to allow
these systems to use the dummy regulator, though it is likely that
unconfigured supplies on such systems will lead to error due to
regulators being powered down more aggressively when not in use.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>

1 files changed, 26 insertions, 1 deletions

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 75a26f78091..c7bbe30010f 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -24,6 +24,8 @@
 #include <linux/regulator/driver.h>
 #include <linux/regulator/machine.h>
 
+#include "dummy.h"
+
 #define REGULATOR_VERSION "0.5"
 
 static DEFINE_MUTEX(regulator_list_mutex);
@@ -1123,6 +1125,22 @@ 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;
 
@@ -2483,8 +2501,15 @@ 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 */