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Commit 5c6e3a97 authored Jun 08, 2015 by Krzysztof Kozlowski Committed by Sebastian Reichel Jun 10, 2015

power_supply: sysfs: Bring back write to writeable properties



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: 8e59c7f2 ("power_supply: Fix NULL pointer dereference during bq27x00_battery probe")
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

parent fb323ecc

drivers/power/power_supply_sysfs.c

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -223,7 +223,7 @@ static umode_t power_supply_attr_is_visible(struct kobject *kobj,

	if (property == attrno) {		if (property == attrno) {
	if (psy->desc->property_is_writeable &&		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;		mode \|= S_IWUSR;

	return mode;		return mode;

include/linux/power_supply.h

+5 −0

Original line number	Original line	Diff line number	Diff line
	@@ -206,6 +206,11 @@ struct power_supply_desc {
	int (set_property)(struct power_supply psy,		int (set_property)(struct power_supply psy,
	enum power_supply_property psp,		enum power_supply_property psp,
	const union power_supply_propval *val);		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,		int (property_is_writeable)(struct power_supply psy,
	enum power_supply_property psp);		enum power_supply_property psp);
	void (external_power_changed)(struct power_supply psy);		void (external_power_changed)(struct power_supply psy);