PM / Runtime: Add sysfs switch for disabling device run-time PM

Add new device sysfs attribute, power/control, allowing the user
space to block the run-time power management of the devices.  If this
attribute is set to "on", the driver of the device won't be able to power
manage it at run time (without breaking the rules) and the device will
always be in the full power state (except when the entire system goes
into a sleep state).

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Alan Stern <stern@rowland.harvard.edu>

1 files changed, 51 insertions, 0 deletions

diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
index 596aeecfdffe..c011ff15632c 100644
--- a/drivers/base/power/sysfs.c
+++ b/drivers/base/power/sysfs.c
@@ -4,9 +4,25 @@
 
 #include <linux/device.h>
 #include <linux/string.h>
+#include <linux/pm_runtime.h>
 #include "power.h"
 
 /*
+ *	control - Report/change current runtime PM setting of the device
+ *
+ *	Runtime power management of a device can be blocked with the help of
+ *	this attribute.  All devices have one of the following two values for
+ *	the power/control file:
+ *
+ *	 + "auto\n" to allow the device to be power managed at run time;
+ *	 + "on\n" to prevent the device from being power managed at run time;
+ *
+ *	The default for all devices is "auto", which means that devices may be
+ *	subject to automatic power management, depending on their drivers.
+ *	Changing this attribute to "on" prevents the driver from power managing
+ *	the device at run time.  Doing that while the device is suspended causes
+ *	it to be woken up.
+ *
  *	wakeup - Report/change current wakeup option for device
  *
  *	Some devices support "wakeup" events, which are hardware signals
@@ -43,6 +59,38 @@
 static const char enabled[] = "enabled";
 static const char disabled[] = "disabled";
 
+#ifdef CONFIG_PM_RUNTIME
+static const char ctrl_auto[] = "auto";
+static const char ctrl_on[] = "on";
+
+static ssize_t control_show(struct device *dev, struct device_attribute *attr,
+			    char *buf)
+{
+	return sprintf(buf, "%s\n",
+				dev->power.runtime_auto ? ctrl_auto : ctrl_on);
+}
+
+static ssize_t control_store(struct device * dev, struct device_attribute *attr,
+			     const char * buf, size_t n)
+{
+	char *cp;
+	int len = n;
+
+	cp = memchr(buf, '\n', n);
+	if (cp)
+		len = cp - buf;
+	if (len == sizeof ctrl_auto - 1 && strncmp(buf, ctrl_auto, len) == 0)
+		pm_runtime_allow(dev);
+	else if (len == sizeof ctrl_on - 1 && strncmp(buf, ctrl_on, len) == 0)
+		pm_runtime_forbid(dev);
+	else
+		return -EINVAL;
+	return n;
+}
+
+static DEVICE_ATTR(control, 0644, control_show, control_store);
+#endif
+
 static ssize_t
 wake_show(struct device * dev, struct device_attribute *attr, char * buf)
 {
@@ -79,6 +127,9 @@ static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store);
 
 
 static struct attribute * power_attrs[] = {
+#ifdef CONFIG_PM_RUNTIME
+	&dev_attr_control.attr,
+#endif
 	&dev_attr_wakeup.attr,
 	NULL,
 };