PM / Runtime: Return special error code if runtime PM is disabled

Some callers of pm_runtime_get_sync() and other runtime PM helper
functions, scsi_autopm_get_host() and scsi_autopm_get_device() in
particular, need to distinguish error codes returned when runtime PM
is disabled (i.e. power.disable_depth is nonzero for the given
device) from error codes returned in other situations.  For this
reason, make the runtime PM helper functions return -EACCES when
power.disable_depth is nonzero and ensure that this error code
won't be returned by them in any other circumstances.  Modify
scsi_autopm_get_host() and scsi_autopm_get_device() to check the
error code returned by pm_runtime_get_sync() and ignore -EACCES.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

Documentation/power/runtime_pm.txt

@@ -291,7 +291,8 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
     - execute the subsystem-level suspend callback for the device; returns 0 on
       success, 1 if the device's run-time PM status was already 'suspended', or
       error code on failure, where -EAGAIN or -EBUSY means it is safe to attempt
-      to suspend the device again in future
+      to suspend the device again in future and -EACCES means that
+      'power.disable_depth' is different from 0
 
   int pm_runtime_autosuspend(struct device *dev);
     - same as pm_runtime_suspend() except that the autosuspend delay is taken
@@ -304,7 +305,8 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
       success, 1 if the device's run-time PM status was already 'active' or
       error code on failure, where -EAGAIN means it may be safe to attempt to
       resume the device again in future, but 'power.runtime_error' should be
-      checked additionally
+      checked additionally, and -EACCES means that 'power.disable_depth' is
+      different from 0
 
   int pm_request_idle(struct device *dev);
     - submit a request to execute the subsystem-level idle callback for the

drivers/base/power/runtime.c

@@ -135,8 +135,9 @@ static int rpm_check_suspend_allowed(struct device *dev)
 
 	if (dev->power.runtime_error)
 		retval = -EINVAL;
-	else if (atomic_read(&dev->power.usage_count) > 0
-	    || dev->power.disable_depth > 0)
+	else if (dev->power.disable_depth > 0)
+		retval = -EACCES;
+	else if (atomic_read(&dev->power.usage_count) > 0)
 		retval = -EAGAIN;
 	else if (!pm_children_suspended(dev))
 		retval = -EBUSY;
@@ -262,7 +263,7 @@ static int rpm_callback(int (*cb)(struct device *), struct device *dev)
 		spin_lock_irq(&dev->power.lock);
 	}
 	dev->power.runtime_error = retval;
-	return retval;
+	return retval != -EACCES ? retval : -EIO;
 }
 
 /**
@@ -458,7 +459,7 @@ static int rpm_resume(struct device *dev, int rpmflags)
 	if (dev->power.runtime_error)
 		retval = -EINVAL;
 	else if (dev->power.disable_depth > 0)
-		retval = -EAGAIN;
+		retval = -EACCES;
 	if (retval)
 		goto out;
 

drivers/scsi/scsi_pm.c

@@ -144,9 +144,9 @@ int scsi_autopm_get_device(struct scsi_device *sdev)
 	int	err;
 
 	err = pm_runtime_get_sync(&sdev->sdev_gendev);
-	if (err < 0)
+	if (err < 0 && err !=-EACCES)
 		pm_runtime_put_sync(&sdev->sdev_gendev);
-	else if (err > 0)
+	else
 		err = 0;
 	return err;
 }
@@ -173,9 +173,9 @@ int scsi_autopm_get_host(struct Scsi_Host *shost)
 	int	err;
 
 	err = pm_runtime_get_sync(&shost->shost_gendev);
-	if (err < 0)
+	if (err < 0 && err !=-EACCES)
 		pm_runtime_put_sync(&shost->shost_gendev);
-	else if (err > 0)
+	else
 		err = 0;
 	return err;
 }