[PATCH] PM / Runtime: Rework RPM get callback routines

[Andrzej Hajda]

PM uses three separate functions to fetch RPM callbacks.
These functions uses quite complicated macro in their body.
The patch replaces these routines with one small macro and
one helper function.

Signed-off-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
---
Hi,

I guess such constructs (offsetof and void* arithmetic) are little bit
controversial. On the other side they seems to me more clear than the
current solution. For sure they produce better code:
   8186	     72	     24	   8282	   205a	drivers/base/power/runtime.old.o
   7938	     72	     24	   8034	   1f62	drivers/base/power/runtime.o

Regards
Andrzej
---
 drivers/base/power/runtime.c | 69 +++++++++++++++++++++-----------------------
 1 file changed, 33 insertions(+), 36 deletions(-)

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 67c7938..8f1ab84 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -13,42 +13,39 @@
 #include <trace/events/rpm.h>
 #include "power.h"
 
-#define RPM_GET_CALLBACK(dev, cb)				\
-({								\
-	int (*__rpm_cb)(struct device *__d);			\
-								\
-	if (dev->pm_domain)					\
-		__rpm_cb = dev->pm_domain->ops.cb;		\
-	else if (dev->type && dev->type->pm)			\
-		__rpm_cb = dev->type->pm->cb;			\
-	else if (dev->class && dev->class->pm)			\
-		__rpm_cb = dev->class->pm->cb;			\
-	else if (dev->bus && dev->bus->pm)			\
-		__rpm_cb = dev->bus->pm->cb;			\
-	else							\
-		__rpm_cb = NULL;				\
-								\
-	if (!__rpm_cb && dev->driver && dev->driver->pm)	\
-		__rpm_cb = dev->driver->pm->cb;			\
-								\
-	__rpm_cb;						\
-})
-
-static int (*rpm_get_suspend_cb(struct device *dev))(struct device *)
-{
-	return RPM_GET_CALLBACK(dev, runtime_suspend);
-}
+typedef int (*pm_callback_t)(struct device *);
 
-static int (*rpm_get_resume_cb(struct device *dev))(struct device *)
+static pm_callback_t __rpm_get_callback(struct device *dev, size_t cb_offset)
 {
-	return RPM_GET_CALLBACK(dev, runtime_resume);
+	pm_callback_t cb;
+	const struct dev_pm_ops *ops;
+
+	if (dev->pm_domain)
+		ops = &dev->pm_domain->ops;
+	else if (dev->type && dev->type->pm)
+		ops = dev->type->pm;
+	else if (dev->class && dev->class->pm)
+		ops = dev->class->pm;
+	else if (dev->bus && dev->bus->pm)
+		ops = dev->bus->pm;
+	else
+		ops = NULL;
+
+	if (ops)
+		cb = *(pm_callback_t *)((void *)ops + cb_offset);
+	else
+		cb = NULL;
+
+	if (!cb && dev->driver && dev->driver->pm)
+		cb = *(pm_callback_t *)((void *)dev->driver->pm + cb_offset);
+
+	return cb;
 }
 
+#define RPM_GET_CALLBACK(dev, callback) \
+		__rpm_get_callback(dev, offsetof(struct dev_pm_ops, callback))
+
 #ifdef CONFIG_PM_RUNTIME
-static int (*rpm_get_idle_cb(struct device *dev))(struct device *)
-{
-	return RPM_GET_CALLBACK(dev, runtime_idle);
-}
 
 static int rpm_resume(struct device *dev, int rpmflags);
 static int rpm_suspend(struct device *dev, int rpmflags);
@@ -347,7 +344,7 @@ static int rpm_idle(struct device *dev, int rpmflags)
 
 	dev->power.idle_notification = true;
 
-	callback = rpm_get_idle_cb(dev);
+	callback = RPM_GET_CALLBACK(dev, runtime_idle);
 
 	if (callback)
 		retval = __rpm_callback(callback, dev);
@@ -517,7 +514,7 @@ static int rpm_suspend(struct device *dev, int rpmflags)
 
 	__update_runtime_status(dev, RPM_SUSPENDING);
 
-	callback = rpm_get_suspend_cb(dev);
+	callback = RPM_GET_CALLBACK(dev, runtime_suspend);
 
 	retval = rpm_callback(callback, dev);
 	if (retval)
@@ -737,7 +734,7 @@ static int rpm_resume(struct device *dev, int rpmflags)
 
 	__update_runtime_status(dev, RPM_RESUMING);
 
-	callback = rpm_get_resume_cb(dev);
+	callback = RPM_GET_CALLBACK(dev, runtime_resume);
 
 	retval = rpm_callback(callback, dev);
 	if (retval) {
@@ -1431,7 +1428,7 @@ int pm_runtime_force_suspend(struct device *dev)
 	if (pm_runtime_status_suspended(dev))
 		return 0;
 
-	callback = rpm_get_suspend_cb(dev);
+	callback = RPM_GET_CALLBACK(dev, runtime_suspend);
 
 	if (!callback) {
 		ret = -ENOSYS;
@@ -1467,7 +1464,7 @@ int pm_runtime_force_resume(struct device *dev)
 	int (*callback)(struct device *);
 	int ret = 0;
 
-	callback = rpm_get_resume_cb(dev);
+	callback = RPM_GET_CALLBACK(dev, runtime_resume);
 
 	if (!callback) {
 		ret = -ENOSYS;
-- 
1.9.1

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