linux-kernel - [PATCH] power_supply: fix return value of get

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Date:	Mon, 13 Jun 2016 17:03:41 -0400
From:	Rhyland Klein <rklein@...dia.com>
To:	Sebastian Reichel <sre@...nel.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>
CC:	<linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Rhyland Klein <rklein@...dia.com>
Subject: [PATCH] power_supply: fix return value of get_property

power_supply_get_property() should ideally return -EAGAIN if it is
called while the power_supply is being registered. There was no way
previously to determine if use_cnt == 0 meant that the power_supply
wasn't fully registered yet, or if it had already been unregistered.

Add a new boolean to the power_supply struct to simply show if
registration is completed.

Signed-off-by: Rhyland Klein <rklein@...dia.com>
---
This patch continues what was discussed with the patch
"power_supply: power_supply_read_temp only if use_cnt > 0".
Looking at the thermal code, it looks like we should indeed return
EAGAIN if possible, and since this change is fairly simple, I think
it makes sense to do it.

 drivers/power/power_supply_core.c | 6 +++++-
 include/linux/power_supply.h      | 1 +
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/power/power_supply_core.c b/drivers/power/power_supply_core.c
index b13cd074c52a..a39a47672979 100644
--- a/drivers/power/power_supply_core.c
+++ b/drivers/power/power_supply_core.c
@@ -491,8 +491,11 @@ int power_supply_get_property(struct power_supply *psy,
 			    enum power_supply_property psp,
 			    union power_supply_propval *val)
 {
-	if (atomic_read(&psy->use_cnt) <= 0)
+	if (atomic_read(&psy->use_cnt) <= 0) {
+		if (!psy->initialized)
+			return -EAGAIN;
 		return -ENODEV;
+	}
 
 	return psy->desc->get_property(psy, psp, val);
 }
@@ -775,6 +778,7 @@ __power_supply_register(struct device *parent,
 	if (rc)
 		goto create_triggers_failed;
 
+	psy->initialized = true;
 	/*
 	 * Update use_cnt after any uevents (most notably from device_add()).
 	 * We are here still during driver's probe but
diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
index 751061790626..3965503315ef 100644
--- a/include/linux/power_supply.h
+++ b/include/linux/power_supply.h
@@ -248,6 +248,7 @@ struct power_supply {
 	struct delayed_work deferred_register_work;
 	spinlock_t changed_lock;
 	bool changed;
+	bool initialized;
 	atomic_t use_cnt;
 #ifdef CONFIG_THERMAL
 	struct thermal_zone_device *tzd;
-- 
1.9.1