[PATCH] [2.6.24-rc] ACPI: register power_supply subdevice only when battery is present

[Andrey Borzenkov <arvidjaar@mail.ru>]

On Sunday 28 October 2007, Andrey Borzenkov wrote:
> On Saturday 27 October 2007, Anton Vorontsov wrote:
> > On Sat, Oct 27, 2007 at 08:54:30PM +0400, Andrey Borzenkov wrote:
> > > I am not exactly sure about this one ... what other power_supply class
> > > drivers do? Should I fix HAL instead (but then, I do not know whether
> > > HAL is the only application that is using this interface).
> >
> > Well, PROP_PRESENT wasn't my idea, currently it's used by pmu and
> > olpc drivers becuase it's not trivial to register/unregister their
> > batteries on physical insertion/removal. I have some plans to teach
> > at least pmu batteries to not use PROP_PRESENT. I don't have any
> > OLPC, thus I can't convert it.
> >
> > To sum this: the good way to handle "missing" batteries is to
> > unregister them, so they'll not show up in the /sys/class/power_supply.
>
> Well, in this case HAL behaviour makes sense (default to present == true
> if "present" attribute is missing)
>
> > Is that possible with the ACPI?
>
> At least looking in ACPI specs, this looks possible. What currently is
> presented as battery object is actually battery bay according to ACPI spec:
>
> Unlike most other devices, when a battery is inserted or removed from the
> system, the device itself (the
> battery bay) is still considered to be present in the system.
>
> When battery is inserted/removed, ACPI notifies us and we can check whether
> battery is actually present and update registration accordingly. From the
> sysfs structure POV probably nothing has to be changed; just when and how
> power_supply is registered
> under /sys/devices/LNXSYSTM:00/device:00/PNP0C0A:0n
>
> Alexey, does it make sense (or doable)?

or would you take attached patch as prototype? :) This works on my system and 
does not crash it immediately. Here is event sequence I get:

UEVENT[1193556388.161539] add      /module/battery (module)
ACTION=add
DEVPATH=/module/battery
SUBSYSTEM=module
SEQNUM=3243

UEVENT[1193556388.177069] add      /bus/acpi/drivers/battery (drivers)
ACTION=add
DEVPATH=/bus/acpi/drivers/battery
SUBSYSTEM=drivers
SEQNUM=3244

UEVENT[1193556388.212721] 
add      /devices/LNXSYSTM:00/device:00/PNP0C0A:00/power_supply/BAT1 
(power_supply)
ACTION=add
DEVPATH=/devices/LNXSYSTM:00/device:00/PNP0C0A:00/power_supply/BAT1
SUBSYSTEM=power_supply
SEQNUM=3245

UEVENT[1193556388.223113] 
change   /devices/LNXSYSTM:00/device:00/PNP0C0A:00/power_supply/BAT1 
(power_supply)
ACTION=change
DEVPATH=/devices/LNXSYSTM:00/device:00/PNP0C0A:00/power_supply/BAT1
SUBSYSTEM=power_supply
POWER_SUPPLY_NAME=BAT1
POWER_SUPPLY_TYPE=Battery
POWER_SUPPLY_STATUS=Full
POWER_SUPPLY_PRESENT=1
POWER_SUPPLY_TECHNOLOGY=Unknown
POWER_SUPPLY_VOLTAGE_MIN_DESIGN=10800000
POWER_SUPPLY_VOLTAGE_NOW=0
POWER_SUPPLY_CURRENT_NOW=0
POWER_SUPPLY_ENERGY_FULL_DESIGN=38880000
POWER_SUPPLY_ENERGY_FULL=37530000
POWER_SUPPLY_ENERGY_NOW=0
POWER_SUPPLY_MODEL_NAME=XM2038P04
POWER_SUPPLY_MANUFACTURER=
SEQNUM=3246

physically remove battery

UEVENT[1193556483.326303] 
remove   /devices/LNXSYSTM:00/device:00/PNP0C0A:00/power_supply/BAT1 
(power_supply)
ACTION=remove
DEVPATH=/devices/LNXSYSTM:00/device:00/PNP0C0A:00/power_supply/BAT1
SUBSYSTEM=power_supply
POWER_SUPPLY_NAME=BAT1
POWER_SUPPLY_TYPE=Battery
POWER_SUPPLY_PRESENT=0
SEQNUM=3252


battery back

UEVENT[1193556510.339045] 
add      /devices/LNXSYSTM:00/device:00/PNP0C0A:00/power_supply/BAT1 
(power_supply)
ACTION=add
DEVPATH=/devices/LNXSYSTM:00/device:00/PNP0C0A:00/power_supply/BAT1
SUBSYSTEM=power_supply
SEQNUM=3253

UEVENT[1193556510.339387] 
change   /devices/LNXSYSTM:00/device:00/PNP0C0A:00/power_supply/BAT1 
(power_supply)
ACTION=change
DEVPATH=/devices/LNXSYSTM:00/device:00/PNP0C0A:00/power_supply/BAT1
SUBSYSTEM=power_supply
POWER_SUPPLY_NAME=BAT1
POWER_SUPPLY_TYPE=Battery
POWER_SUPPLY_STATUS=Charging
POWER_SUPPLY_PRESENT=1
POWER_SUPPLY_TECHNOLOGY=Unknown
POWER_SUPPLY_VOLTAGE_MIN_DESIGN=10800000
POWER_SUPPLY_VOLTAGE_NOW=11340000
POWER_SUPPLY_CURRENT_NOW=13197000
POWER_SUPPLY_ENERGY_FULL_DESIGN=38880000
POWER_SUPPLY_ENERGY_FULL=37530000
POWER_SUPPLY_ENERGY_NOW=37519000
POWER_SUPPLY_MODEL_NAME=XM2038P04
POWER_SUPPLY_MANUFACTURER=
SEQNUM=3254

We'll probably need to teach user space to distinguish between battery and 
battery bay (and not to crash when battery is removed :) ) but that is all 
doable once we settle on kernel implementation.

Subject: [PATCH] [2.6.24-rc] ACPI: register power_supply subdevice only when battery is present
From: Andrey Borzenkov <arvidjaar@mail.ru>

Make sure no power_supply object is present unless we actualy detect
presence of battery. This fixes ghost batteries detected by HAL

Signed-off-by: Andrey Borzenkov <arvidjaar@mail.ru>

---

 drivers/acpi/battery.c |   98 ++++++++++++++++++++++++++++++------------------
 1 files changed, 61 insertions(+), 37 deletions(-)

diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
index d33cb49..f37e509 100644
--- a/drivers/acpi/battery.c
+++ b/drivers/acpi/battery.c
@@ -390,14 +390,64 @@ static int acpi_battery_init_alarm(struct acpi_battery *battery)
 	return acpi_battery_set_alarm(battery);
 }
 
+static ssize_t acpi_battery_alarm_show(struct device *dev,
+					struct device_attribute *attr,
+					char *buf)
+{
+	struct acpi_battery *battery = to_acpi_battery(dev_get_drvdata(dev));
+	return sprintf(buf, "%d\n", battery->alarm * 1000);
+}
+
+static ssize_t acpi_battery_alarm_store(struct device *dev,
+					struct device_attribute *attr,
+					const char *buf, size_t count)
+{
+	unsigned long x;
+	struct acpi_battery *battery = to_acpi_battery(dev_get_drvdata(dev));
+	if (sscanf(buf, "%ld\n", &x) == 1)
+		battery->alarm = x/1000;
+	if (acpi_battery_present(battery))
+		acpi_battery_set_alarm(battery);
+	return count;
+}
+
+static struct device_attribute alarm_attr = {
+	.attr = {.name = "alarm", .mode = 0644, .owner = THIS_MODULE},
+	.show = acpi_battery_alarm_show,
+	.store = acpi_battery_alarm_store,
+};
+
+static int sysfs_add_battery(struct acpi_battery *battery)
+{
+	int result = 0;
+
+	result = power_supply_register(&battery->device->dev, &battery->bat);
+	result = device_create_file(battery->bat.dev, &alarm_attr);
+
+	return result;
+}
+
+static int sysfs_remove_battery(struct acpi_battery *battery)
+{
+	if (battery->bat.dev) {
+		device_remove_file(battery->bat.dev, &alarm_attr);
+		power_supply_unregister(&battery->bat);
+		battery->bat.dev = NULL;
+	}
+
+	return 0;
+}
+
 static int acpi_battery_update(struct acpi_battery *battery)
 {
-	int saved_present = acpi_battery_present(battery);
 	int result = acpi_battery_get_status(battery);
-	if (result || !acpi_battery_present(battery))
+	if (result)
 		return result;
-	if (saved_present != acpi_battery_present(battery) ||
-	    !battery->update_time) {
+	if (!acpi_battery_present(battery)) {
+		sysfs_remove_battery(battery);
+		return 0;
+	}
+	if (!battery->bat.dev) {
 		battery->update_time = 0;
 		result = acpi_battery_get_info(battery);
 		if (result)
@@ -411,6 +461,7 @@ static int acpi_battery_update(struct acpi_battery *battery)
 			battery->bat.num_properties =
 				ARRAY_SIZE(energy_battery_props);
 		}
+		sysfs_add_battery(battery);
 		acpi_battery_init_alarm(battery);
 	}
 	return acpi_battery_get_state(battery);
@@ -693,33 +744,6 @@ static void acpi_battery_remove_fs(struct acpi_device *device)
 
 #endif
 
-static ssize_t acpi_battery_alarm_show(struct device *dev,
-					struct device_attribute *attr,
-					char *buf)
-{
-	struct acpi_battery *battery = to_acpi_battery(dev_get_drvdata(dev));
-	return sprintf(buf, "%d\n", battery->alarm * 1000);
-}
-
-static ssize_t acpi_battery_alarm_store(struct device *dev,
-					struct device_attribute *attr,
-					const char *buf, size_t count)
-{
-	unsigned long x;
-	struct acpi_battery *battery = to_acpi_battery(dev_get_drvdata(dev));
-	if (sscanf(buf, "%ld\n", &x) == 1)
-		battery->alarm = x/1000;
-	if (acpi_battery_present(battery))
-		acpi_battery_set_alarm(battery);
-	return count;
-}
-
-static struct device_attribute alarm_attr = {
-	.attr = {.name = "alarm", .mode = 0644, .owner = THIS_MODULE},
-	.show = acpi_battery_alarm_show,
-	.store = acpi_battery_alarm_store,
-};
-
 /* --------------------------------------------------------------------------
                                  Driver Interface
    -------------------------------------------------------------------------- */
@@ -737,7 +761,9 @@ static void acpi_battery_notify(acpi_handle handle, u32 event, void *data)
 	acpi_bus_generate_netlink_event(device->pnp.device_class,
 					device->dev.bus_id, event,
 					acpi_battery_present(battery));
-	kobject_uevent(&battery->bat.dev->kobj, KOBJ_CHANGE);
+	/* acpi_batter_update could remove power_supply object */
+	if (battery->bat.dev)
+		kobject_uevent(&battery->bat.dev->kobj, KOBJ_CHANGE);
 }
 
 static int acpi_battery_add(struct acpi_device *device)
@@ -755,17 +781,15 @@ static int acpi_battery_add(struct acpi_device *device)
 	strcpy(acpi_device_class(device), ACPI_BATTERY_CLASS);
 	acpi_driver_data(device) = battery;
 	mutex_init(&battery->lock);
+	battery->bat.name = acpi_device_bid(device);
+	battery->bat.type = POWER_SUPPLY_TYPE_BATTERY;
+	battery->bat.get_property = acpi_battery_get_property;
 	acpi_battery_update(battery);
 #ifdef CONFIG_ACPI_PROCFS
 	result = acpi_battery_add_fs(device);
 	if (result)
 		goto end;
 #endif
-	battery->bat.name = acpi_device_bid(device);
-	battery->bat.type = POWER_SUPPLY_TYPE_BATTERY;
-	battery->bat.get_property = acpi_battery_get_property;
-	result = power_supply_register(&battery->device->dev, &battery->bat);
-	result = device_create_file(battery->bat.dev, &alarm_attr);
 	status = acpi_install_notify_handler(device->handle,
 					     ACPI_ALL_NOTIFY,
 					     acpi_battery_notify, battery);

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