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

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Date:	Sun, 28 Oct 2007 11:37:26 +0400
From:	Andrey Borzenkov <arvidjaar@...l.ru>
To:	cbou@...l.ru
Cc:	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	dwmw2@...radead.org, Alexey Starikovskiy <aystarik@...il.com>
Subject: [PATCH] [2.6.24-rc] ACPI: register power_supply subdevice only when battery is present

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.

View attachment "fix_ACPI_battery_registration" of type "text/x-diff" (5390 bytes)

Download attachment "signature.asc " of type "application/pgp-signature" (190 bytes)