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Date:   Mon, 03 Apr 2017 18:04:58 +0200
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     "mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Ramiro.Oliveira@...opsys.com" <Ramiro.Oliveira@...opsys.com>
Subject: Re: [PATCH v1] reset: Make optional stuff optional for all users

On Mon, 2017-04-03 at 18:23 +0300, Andy Shevchenko wrote:
> On Mon, 2017-04-03 at 17:09 +0200, Philipp Zabel wrote:
> > On Mon, 2017-04-03 at 14:33 +0000, Shevchenko, Andriy wrote:
> > > On Mon, 2017-04-03 at 17:31 +0300, Andy Shevchenko wrote:
> > > > On Mon, 2017-04-03 at 16:27 +0200, Philipp Zabel wrote:
> > > > > 
> > > > > >  	int rstc_id;
> > > > > >  	int ret;
> > > > > >  
> > > > > > -	if (!node)
> > > > > > -		return ERR_PTR(-EINVAL);
> > > > > > -
> > > > > 
> > > > > This should be
> > > > > 
> > > > > 	if (!node)
> > > > > 		return optional ? NULL : ERR_PTR(-EINVAL);
> > > > > 
> > > > > instead. Can you confirm this works for Intel boards with DW
> > > > > UART? I
> > > > > can
> > > > > fix it up when applying if you agree.
> > > > 
> > > > I don't think it worth to change. I specifically checked all of_*
> > > > calls
> > > > in that function and they cope pretty nice with node == NULL.
> > 
> > __of_reset_control_get called with id != NULL calls
> > of_property_match_string first, which then returns -EINVAL if
> > node == NULL, which makes __of_reset_control_get return NULL if
> > optional
> > or -ENOENT otherwise, even though the correct return value would be
> > -EINVAL in the DT case.
> 
> Error handling mess as usual. :-)
>
> > 
> > __of_reset_control_get called with id == NULL calls
> > of_parse_phandle_with_args first, which calls
> > __of_parse_phandle_with_args, which returns an undefined value if
> > np == NULL, as far as I can tell:
> > of_for_each_phandle first calls of_phandle_iterator_init, which, when
> > called with np == NULL clears the iterator structure returns -ENOENT.
> > The return value is ignored in the of_for_each_phandle macro, and
> > of_phandle_iterator_next is then called and returns -ENOENT because
> > it->cur == NULL, ending the loop without ever assigning a value to rc.
> > __of_parse_phandle_with_args then returns the uninitialized value.
> 
> It returns -ENOENT. Error value is kept in function variable rc.

Thanks for the correction. That's still the wrong error code IMHO, but
it certainly makes your patch unproblematic.

> > The point being, instead of having to regularly forage through a
> > number
> > of of_ API functions to make sure my expectations are still met, I'd
> > prefer to keep the check in place.
> 
> I would not insist, I already shared my view on this.

Appreciated. With a correct understanding of the current of_* error
return paths it makes a lot more sense.

> I really don't like ping-ponging of the code. Perhaps you would fix it
> once for the best now?

How about:

----------8<----------
>From 75205aeaf52cef5c62710630cceb871468175c12 Mon Sep 17 00:00:00 2001
From: Philipp Zabel <p.zabel@...gutronix.de>
Date: Fri, 5 Feb 2016 13:41:39 +0100
Subject: [PATCH] reset: add exported __reset_control_get, return NULL if
 optional

Rename the internal __reset_control_get/put functions to
__reset_control_get/put_internal and add an exported
__reset_control_get equivalent to __of_reset_control_get
that takes a struct device parameter.
This avoids the confusing call to __of_reset_control_get in
the non-DT case and fixes the devm_reset_control_get_optional
function to return NULL if RESET_CONTROLLER is enabled but
dev->of_node == NULL.

Fixes: bb475230b8e5 ("reset: make optional functions really optional")
Reported-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Ramiro Oliveira <Ramiro.Oliveira@...opsys.com>
Signed-off-by: Philipp Zabel <p.zabel@...gutronix.de>
---
 drivers/reset/core.c  | 22 ++++++++++++++++------
 include/linux/reset.h | 22 ++++++++++++++--------
 2 files changed, 30 insertions(+), 14 deletions(-)

diff --git a/drivers/reset/core.c b/drivers/reset/core.c
index f1e5e65388bb5..d227168c8971a 100644
--- a/drivers/reset/core.c
+++ b/drivers/reset/core.c
@@ -275,7 +275,7 @@ int reset_control_status(struct reset_control *rstc)
 }
 EXPORT_SYMBOL_GPL(reset_control_status);
 
-static struct reset_control *__reset_control_get(
+static struct reset_control *__reset_control_get_internal(
 				struct reset_controller_dev *rcdev,
 				unsigned int index, bool shared)
 {
@@ -308,7 +308,7 @@ static struct reset_control *__reset_control_get(
 	return rstc;
 }
 
-static void __reset_control_put(struct reset_control *rstc)
+static void __reset_control_put_internal(struct reset_control *rstc)
 {
 	lockdep_assert_held(&reset_list_mutex);
 
@@ -377,7 +377,7 @@ struct reset_control *__of_reset_control_get(struct device_node *node,
 	}
 
 	/* reset_list_mutex also protects the rcdev's reset_control list */
-	rstc = __reset_control_get(rcdev, rstc_id, shared);
+	rstc = __reset_control_get_internal(rcdev, rstc_id, shared);
 
 	mutex_unlock(&reset_list_mutex);
 
@@ -385,6 +385,17 @@ struct reset_control *__of_reset_control_get(struct device_node *node,
 }
 EXPORT_SYMBOL_GPL(__of_reset_control_get);
 
+struct reset_control *__reset_control_get(struct device *dev, const char *id,
+					  int index, bool shared, bool optional)
+{
+	if (dev->of_node)
+		return __of_reset_control_get(dev->of_node, id, index, shared,
+					      optional);
+	else
+		return optional ? NULL : ERR_PTR(-EINVAL);
+}
+EXPORT_SYMBOL_GPL(__reset_control_get);
+
 /**
  * reset_control_put - free the reset controller
  * @rstc: reset controller
@@ -396,7 +407,7 @@ void reset_control_put(struct reset_control *rstc)
 		return;
 
 	mutex_lock(&reset_list_mutex);
-	__reset_control_put(rstc);
+	__reset_control_put_internal(rstc);
 	mutex_unlock(&reset_list_mutex);
 }
 EXPORT_SYMBOL_GPL(reset_control_put);
@@ -417,8 +428,7 @@ struct reset_control *__devm_reset_control_get(struct device *dev,
 	if (!ptr)
 		return ERR_PTR(-ENOMEM);
 
-	rstc = __of_reset_control_get(dev ? dev->of_node : NULL,
-				      id, index, shared, optional);
+	rstc = __reset_control_get(dev, id, index, shared, optional);
 	if (!IS_ERR(rstc)) {
 		*ptr = rstc;
 		devres_add(dev, ptr);
diff --git a/include/linux/reset.h b/include/linux/reset.h
index 96fb139bdd08f..13d8681210d54 100644
--- a/include/linux/reset.h
+++ b/include/linux/reset.h
@@ -15,6 +15,9 @@ int reset_control_status(struct reset_control *rstc);
 struct reset_control *__of_reset_control_get(struct device_node *node,
 				     const char *id, int index, bool shared,
 				     bool optional);
+struct reset_control *__reset_control_get(struct device *dev, const char *id,
+					  int index, bool shared,
+					  bool optional);
 void reset_control_put(struct reset_control *rstc);
 struct reset_control *__devm_reset_control_get(struct device *dev,
 				     const char *id, int index, bool shared,
@@ -72,6 +75,13 @@ static inline struct reset_control *__of_reset_control_get(
 	return optional ? NULL : ERR_PTR(-ENOTSUPP);
 }
 
+static inline struct reset_control *__reset_control_get(
+					struct device *dev, const char *id,
+					int index, bool shared, bool optional)
+{
+	return optional ? NULL : ERR_PTR(-ENOTSUPP);
+}
+
 static inline struct reset_control *__devm_reset_control_get(
 					struct device *dev, const char *id,
 					int index, bool shared, bool optional)
@@ -102,8 +112,7 @@ __must_check reset_control_get_exclusive(struct device *dev, const char *id)
 #ifndef CONFIG_RESET_CONTROLLER
 	WARN_ON(1);
 #endif
-	return __of_reset_control_get(dev ? dev->of_node : NULL, id, 0, false,
-									false);
+	return __reset_control_get(dev, id, 0, false, false);
 }
 
 /**
@@ -131,22 +140,19 @@ __must_check reset_control_get_exclusive(struct device *dev, const char *id)
 static inline struct reset_control *reset_control_get_shared(
 					struct device *dev, const char *id)
 {
-	return __of_reset_control_get(dev ? dev->of_node : NULL, id, 0, true,
-									false);
+	return __reset_control_get(dev, id, 0, true, false);
 }
 
 static inline struct reset_control *reset_control_get_optional_exclusive(
 					struct device *dev, const char *id)
 {
-	return __of_reset_control_get(dev ? dev->of_node : NULL, id, 0, false,
-									true);
+	return __reset_control_get(dev, id, 0, false, true);
 }
 
 static inline struct reset_control *reset_control_get_optional_shared(
 					struct device *dev, const char *id)
 {
-	return __of_reset_control_get(dev ? dev->of_node : NULL, id, 0, true,
-									true);
+	return __reset_control_get(dev, id, 0, true, true);
 }
 
 /**
-- 
2.11.0
---------->8----------

That should make both the __reset_control_get stub and implementation
return NULL if optional && (dev->of_node == NULL), and stop calling
__of_reset_control_get in the non-DT case, while maintaining the -EINVAL
error return value if of_reset_control_get* is called with node == NULL.

regards
Philipp

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