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Subject[PATCH] power_supply: sysfs: Bring back write to writeable properties
Date
The fix for NULL pointer exception related to calling uevent for not
finished probe caused to set all writeable properties as non-writeable.
This was caused by checking if property is writeable before the initial
increase of power supply usage counter and in the same time using
wrapper over property_is_writeable(). The wrapper returns ENODEV if the
usage counter is still 0.

The call trace looked like:
device probe:
power_supply_register()
use_cnt = 0;
device_add()
create sysfs entries
power_supply_attr_is_visible()
power_supply_property_is_writeable()
if (use_cnt == 0) return -ENODEV;
use_cnt++;

Replace the usage of wrapper with direct call to property_is_writeable()
from driver. This should be safe call during device probe because
implementations of this callback just return 0/1 for different
properties and they do not access any of the driver's internal data.

Fixes: 8e59c7f23410 ("power_supply: Fix NULL pointer dereference during bq27x00_battery probe")
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
---
drivers/power/power_supply_sysfs.c | 2 +-
include/linux/power_supply.h | 5 +++++
2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/power/power_supply_sysfs.c b/drivers/power/power_supply_sysfs.c
index af026806cba5..ed2d7fd0c734 100644
--- a/drivers/power/power_supply_sysfs.c
+++ b/drivers/power/power_supply_sysfs.c
@@ -223,7 +223,7 @@ static umode_t power_supply_attr_is_visible(struct kobject *kobj,

if (property == attrno) {
if (psy->desc->property_is_writeable &&
- power_supply_property_is_writeable(psy, property) > 0)
+ psy->desc->property_is_writeable(psy, property) > 0)
mode |= S_IWUSR;

return mode;
diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
index a80f1fd01ddb..0395bcb18ddb 100644
--- a/include/linux/power_supply.h
+++ b/include/linux/power_supply.h
@@ -206,6 +206,11 @@ struct power_supply_desc {
int (*set_property)(struct power_supply *psy,
enum power_supply_property psp,
const union power_supply_propval *val);
+ /*
+ * property_is_writeable() will be called during registration
+ * of power supply. If this happens during device probe then it must
+ * not access internal data of device (because probe did not end).
+ */
int (*property_is_writeable)(struct power_supply *psy,
enum power_supply_property psp);
void (*external_power_changed)(struct power_supply *psy);
--
1.9.1


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