PM / Runtime: Add no_callbacks flag

Some devices, such as USB interfaces, cannot be power-managed
independently of their parents, i.e., they cannot be put in low power
while the parent remains at full power.  This patch (as1425) creates a
new "no_callbacks" flag, which tells the PM core not to invoke the
runtime-PM callback routines for the such devices but instead to
assume that the callbacks always succeed.  In addition, the
non-debugging runtime-PM sysfs attributes for the devices are removed,
since they are pretty much meaningless.

The advantage of this scheme comes not so much from avoiding the
callbacks themselves, but rather from the fact that without the need
for a process context in which to run the callbacks, more work can be
done in interrupt context.

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

1 files changed, 49 insertions, 7 deletions

diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
index 8859780817e1..b5708c47ce2d 100644
--- a/drivers/base/power/sysfs.c
+++ b/drivers/base/power/sysfs.c
@@ -81,6 +81,9 @@
 static const char enabled[] = "enabled";
 static const char disabled[] = "disabled";
 
+const char power_group_name[] = "power";
+EXPORT_SYMBOL_GPL(power_group_name);
+
 #ifdef CONFIG_PM_RUNTIME
 static const char ctrl_auto[] = "auto";
 static const char ctrl_on[] = "on";
@@ -390,12 +393,6 @@ static DEVICE_ATTR(async, 0644, async_show, async_store);
 #endif /* CONFIG_PM_ADVANCED_DEBUG */
 
 static struct attribute * power_attrs[] = {
-#ifdef CONFIG_PM_RUNTIME
-        &dev_attr_control.attr,
-        &dev_attr_runtime_status.attr,
-        &dev_attr_runtime_suspended_time.attr,
-        &dev_attr_runtime_active_time.attr,
-#endif
         &dev_attr_wakeup.attr,
 #ifdef CONFIG_PM_SLEEP
         &dev_attr_wakeup_count.attr,
@@ -409,6 +406,7 @@ static struct attribute * power_attrs[] = {
 #ifdef CONFIG_PM_ADVANCED_DEBUG
         &dev_attr_async.attr,
 #ifdef CONFIG_PM_RUNTIME
+        &dev_attr_runtime_status.attr,
         &dev_attr_runtime_usage.attr,
         &dev_attr_runtime_active_kids.attr,
         &dev_attr_runtime_enabled.attr,
@@ -417,10 +415,52 @@ static struct attribute * power_attrs[] = {
         NULL,
 };
 static struct attribute_group pm_attr_group = {
-        .name   = "power",
+        .name   = power_group_name,
         .attrs  = power_attrs,
 };
 
+#ifdef CONFIG_PM_RUNTIME
+
+static struct attribute *runtime_attrs[] = {
+#ifndef CONFIG_PM_ADVANCED_DEBUG
+        &dev_attr_runtime_status.attr,
+#endif
+        &dev_attr_control.attr,
+        &dev_attr_runtime_suspended_time.attr,
+        &dev_attr_runtime_active_time.attr,
+        NULL,
+};
+static struct attribute_group pm_runtime_attr_group = {
+        .name   = power_group_name,
+        .attrs  = runtime_attrs,
+};
+
+int dpm_sysfs_add(struct device *dev)
+{
+        int rc;
+
+        rc = sysfs_create_group(&dev->kobj, &pm_attr_group);
+        if (rc == 0 && !dev->power.no_callbacks) {
+                rc = sysfs_merge_group(&dev->kobj, &pm_runtime_attr_group);
+                if (rc)
+                        sysfs_remove_group(&dev->kobj, &pm_attr_group);
+        }
+        return rc;
+}
+
+void rpm_sysfs_remove(struct device *dev)
+{
+        sysfs_unmerge_group(&dev->kobj, &pm_runtime_attr_group);
+}
+
+void dpm_sysfs_remove(struct device *dev)
+{
+        rpm_sysfs_remove(dev);
+        sysfs_remove_group(&dev->kobj, &pm_attr_group);
+}
+
+#else /* CONFIG_PM_RUNTIME */
+
 int dpm_sysfs_add(struct device * dev)
 {
         return sysfs_create_group(&dev->kobj, &pm_attr_group);
@@ -430,3 +470,5 @@ void dpm_sysfs_remove(struct device * dev)
 {
         sysfs_remove_group(&dev->kobj, &pm_attr_group);
 }
+
+#endif