[PATCH] PM / OPP: predictable fail results for opp_find* functions

[Nishanth Menon]

Currently the opp_find* functions return -ENODEV when:
a) it cant find a device (e.g. request for an OPP search on device
   which was not registered)
b) When it cant find a match for the search strategy used

This makes life a little in-efficient for users such as devfreq
to make reasonable judgement before switching search strategies.

So, standardize the return results as following:
 -EINVAL for bad pointer parameters
 -ENODEV when device cannot be found
 -ERANGE when search fails

This has the following benefit for devfreq implementation:

Current code:
opp = opp_find_freq_floor(dev, freq);
/* Following search triggers even for un-registered device */
if (opp == ERR_PTR(-ENODEV))
	opp = opp_find_freq_ceil(dev, freq);

Vs (after this change):
opp = opp_find_freq_floor(dev, freq);
/* Will only be triggered if search logic fails: intended usage */
if (opp == ERR_PTR(-ERANGE))
	opp = opp_find_freq_ceil(dev, freq);

Cc: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
Cc: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxx>
Cc: Kevin Hilman <khilman@xxxxxx>
Cc: linux-pm@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx

Signed-off-by: Nishanth Menon <nm@xxxxxx>
---
 drivers/base/power/opp.c  |   27 +++++++++++++++++++--------
 drivers/devfreq/devfreq.c |    4 ++--
 2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c
index 04d443f..a60a8d1 100644
--- a/drivers/base/power/opp.c
+++ b/drivers/base/power/opp.c
@@ -233,7 +233,10 @@ EXPORT_SYMBOL(opp_get_opp_count);
  *
  * Searches for exact match in the opp list and returns pointer to the matching
  * opp if found, else returns ERR_PTR in case of error and should be handled
- * using IS_ERR.
+ * using IS_ERR. Error return values can be:
+ * EINVAL:	for bad pointer
+ * ERANGE:	no match found for search
+ * ENODEV:	if device not found in list of registered devices
  *
  * Note: available is a modifier for the search. if available=true, then the
  * match is for exact matching frequency and is available in the stored OPP
@@ -252,7 +255,7 @@ struct opp *opp_find_freq_exact(struct device *dev, unsigned long freq,
 				bool available)
 {
 	struct device_opp *dev_opp;
-	struct opp *temp_opp, *opp = ERR_PTR(-ENODEV);
+	struct opp *temp_opp, *opp = ERR_PTR(-ERANGE);
 
 	dev_opp = find_device_opp(dev);
 	if (IS_ERR(dev_opp)) {
@@ -282,7 +285,11 @@ EXPORT_SYMBOL(opp_find_freq_exact);
  * for a device.
  *
  * Returns matching *opp and refreshes *freq accordingly, else returns
- * ERR_PTR in case of error and should be handled using IS_ERR.
+ * ERR_PTR in case of error and should be handled using IS_ERR. Error return
+ * values can be:
+ * EINVAL:	for bad pointer
+ * ERANGE:	no match found for search
+ * ENODEV:	if device not found in list of registered devices
  *
  * Locking: This function must be called under rcu_read_lock(). opp is a rcu
  * protected pointer. The reason for the same is that the opp pointer which is
@@ -293,7 +300,7 @@ EXPORT_SYMBOL(opp_find_freq_exact);
 struct opp *opp_find_freq_ceil(struct device *dev, unsigned long *freq)
 {
 	struct device_opp *dev_opp;
-	struct opp *temp_opp, *opp = ERR_PTR(-ENODEV);
+	struct opp *temp_opp, *opp = ERR_PTR(-ERANGE);
 
 	if (!dev || !freq) {
 		dev_err(dev, "%s: Invalid argument freq=%p\n", __func__, freq);
@@ -302,7 +309,7 @@ struct opp *opp_find_freq_ceil(struct device *dev, unsigned long *freq)
 
 	dev_opp = find_device_opp(dev);
 	if (IS_ERR(dev_opp))
-		return opp;
+		return ERR_CAST(dev_opp);
 
 	list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node) {
 		if (temp_opp->available && temp_opp->rate >= *freq) {
@@ -325,7 +332,11 @@ EXPORT_SYMBOL(opp_find_freq_ceil);
  * for a device.
  *
  * Returns matching *opp and refreshes *freq accordingly, else returns
- * ERR_PTR in case of error and should be handled using IS_ERR.
+ * ERR_PTR in case of error and should be handled using IS_ERR. Error return
+ * values can be:
+ * EINVAL:	for bad pointer
+ * ERANGE:	no match found for search
+ * ENODEV:	if device not found in list of registered devices
  *
  * Locking: This function must be called under rcu_read_lock(). opp is a rcu
  * protected pointer. The reason for the same is that the opp pointer which is
@@ -336,7 +347,7 @@ EXPORT_SYMBOL(opp_find_freq_ceil);
 struct opp *opp_find_freq_floor(struct device *dev, unsigned long *freq)
 {
 	struct device_opp *dev_opp;
-	struct opp *temp_opp, *opp = ERR_PTR(-ENODEV);
+	struct opp *temp_opp, *opp = ERR_PTR(-ERANGE);
 
 	if (!dev || !freq) {
 		dev_err(dev, "%s: Invalid argument freq=%p\n", __func__, freq);
@@ -345,7 +356,7 @@ struct opp *opp_find_freq_floor(struct device *dev, unsigned long *freq)
 
 	dev_opp = find_device_opp(dev);
 	if (IS_ERR(dev_opp))
-		return opp;
+		return ERR_CAST(dev_opp);
 
 	list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node) {
 		if (temp_opp->available) {
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index e4d48d2..3838f99 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -656,14 +656,14 @@ struct opp *devfreq_recommended_opp(struct device *dev, unsigned long *freq,
 		opp = opp_find_freq_floor(dev, freq);
 
 		/* If not available, use the closest opp */
-		if (opp == ERR_PTR(-ENODEV))
+		if (opp == ERR_PTR(-ERANGE))
 			opp = opp_find_freq_ceil(dev, freq);
 	} else {
 		/* The freq is an lower bound. opp should be higher */
 		opp = opp_find_freq_ceil(dev, freq);
 
 		/* If not available, use the closest opp */
-		if (opp == ERR_PTR(-ENODEV))
+		if (opp == ERR_PTR(-ERANGE))
 			opp = opp_find_freq_floor(dev, freq);
 	}
 
-- 
1.7.9.5

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