linux-kernel - [PATCH v4 13/20] power_supply: Increment power supply use counter when obtaining references

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Date:	Mon, 23 Feb 2015 12:47:34 +0100
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Sebastian Reichel <sre@...nel.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <lenb@...nel.org>, Jiri Kosina <jkosina@...e.cz>,
	David Herrmann <dh.herrmann@...glemail.com>,
	Cezary Jackiewicz <cezary.jackiewicz@...il.com>,
	Darren Hart <dvhart@...radead.org>,
	Support Opensource <support.opensource@...semi.com>,
	Milo Kim <milo.kim@...com>,
	Julian Andres Klode <jak@...-linux.org>,
	Marc Dietrich <marvin24@....de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-acpi@...r.kernel.org, linux-input@...r.kernel.org,
	platform-driver-x86@...r.kernel.org,
	patches@...nsource.wolfsonmicro.com, ac100@...ts.launchpad.net,
	linux-tegra@...r.kernel.org, devel@...verdev.osuosl.org,
	Linus Walleij <linus.walleij@...aro.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>,
	linux-arm-kernel@...ts.infradead.org,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Daniel Mack <daniel@...que.org>,
	Haojian Zhuang <haojian.zhuang@...il.com>,
	Robert Jarzmik <robert.jarzmik@...e.fr>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Pavel Machek <pavel@....cz>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Subject: [PATCH v4 13/20] power_supply: Increment power supply use counter when
 obtaining references

Increment the power_supply.use_cnt usage counter on:
 - power_supply_get_by_phandle()
 - power_supply_get_by_name()
and decrement it on power_supply_put() call.

This helps tracking of valid usage of power supply instance by
consumers. The usage counter itself also allows safe calling of
power_supply_get_property-like functions even when driver unregisters
this power supply.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
Reviewed-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
---
 drivers/power/power_supply_core.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/power/power_supply_core.c b/drivers/power/power_supply_core.c
index a94f8c9d5e1e..819430a0bfa6 100644
--- a/drivers/power/power_supply_core.c
+++ b/drivers/power/power_supply_core.c
@@ -349,10 +349,16 @@ static int power_supply_match_device_by_name(struct device *dev, const void *dat
  */
 struct power_supply *power_supply_get_by_name(const char *name)
 {
+	struct power_supply *psy = NULL;
 	struct device *dev = class_find_device(power_supply_class, NULL, name,
 					power_supply_match_device_by_name);
 
-	return dev ? dev_get_drvdata(dev) : NULL;
+	if (dev) {
+		psy = dev_get_drvdata(dev);
+		atomic_inc(&psy->use_cnt);
+	}
+
+	return psy;
 }
 EXPORT_SYMBOL_GPL(power_supply_get_by_name);
 
@@ -367,6 +373,7 @@ void power_supply_put(struct power_supply *psy)
 {
 	might_sleep();
 
+	atomic_dec(&psy->use_cnt);
 	put_device(&psy->dev);
 }
 EXPORT_SYMBOL_GPL(power_supply_put);
@@ -393,6 +400,7 @@ struct power_supply *power_supply_get_by_phandle(struct device_node *np,
 							const char *property)
 {
 	struct device_node *power_supply_np;
+	struct power_supply *psy = NULL;
 	struct device *dev;
 
 	power_supply_np = of_parse_phandle(np, property, 0);
@@ -404,7 +412,12 @@ struct power_supply *power_supply_get_by_phandle(struct device_node *np,
 
 	of_node_put(power_supply_np);
 
-	return dev ? dev_get_drvdata(dev) : NULL;
+	if (dev) {
+		psy = dev_get_drvdata(dev);
+		atomic_inc(&psy->use_cnt);
+	}
+
+	return psy;
 }
 EXPORT_SYMBOL_GPL(power_supply_get_by_phandle);
 #endif /* CONFIG_OF */
-- 
1.9.1

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