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freebsd-skq/share/man/man4/acpi_battery.4
hrs 4f4d8e5e8e Add _BIX (Battery Information Extended) object support. 
ACPI Control Method Batteries have a _BIF and/or _BIX object which
provide static properties of the battery.  FreeBSD acpi_cmbat module
supported _BIF object only, which was deprecated as of ACPI 4.0.
_BIX is an extended version of _BIF defined in ACPI 4.0 or later.

As of writing, _BIX has two revisions.  One is in ACPI 4.0 (rev.0) and
another is in ACPI 6.0 (rev.1).  It seems that hardware vendors still
stick to _BIF only or _BIX rev.0 + _BIF for the maximum compatibility.
Microsoft requires _BIX rev.0 for Windows machines, so there are some
laptop machines with _BIX rev.0 only. In this case, FreeBSD does not
recognize the battery information.

After this change, the acpi_cmbat module gets battery information from
_BIX or _BIF object and internally uses _BIX rev.1 data structure as
the primary information store in the kernel.  ACPIIO_BATT_GET_BI[FX]
returns an acpi_bi[fx] structure built by using information obtained
from a _BIF or a _BIX object found on the system.  The revision number
field can be used to check which field is available.  The acpiconf(8)
utility will show additional information if _BIX is available.

Although ABIs of ACPIIO_BATT_* were changed, the existing APIs for
userland utilities are not changed and the backward-compatible ABIs
are provided.  This means that older versions of acpiconf(8) can also
work with the new kernel. The (union acpi_battery_ioctl_arg) was
padded to 256 byte long to avoid another ABI change in the future.
A _BIX object with its revision number >1 will be treated as
compatible with the rev.1 _BIX format.

Reviewed by:	takawata
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D23728
2020-02-19 06:28:55 +00:00

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.\"
.\" Copyright (c) 2019 Takanori Watanabe
.\" All rights reserved.
.\"
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.\" $FreeBSD$
.\"
.Dd February 16, 2020
.Dt ACPI_BATTERY 4
.Os
.Sh NAME
.Nm acpi_battery
.Nd ACPI battery management subsystem
.Sh SYNOPSIS
.Cd "device acpi"
.Sh DESCRIPTION
The
.Nm
is a driver for battery management features of the ACPI module.
.Pp
An ACPI-compatible battery device supports either a Control
Method Battery interface or a Smart Battery subsystem interface.
The former is accessed by the AML
.Pq ACPI Machine Language
code control methods,
and the latter is controlled directly through the ACPI EC
.Pq Embedded Controller
typically via an SMBus interface.
.Pp
This driver supports the
.Xr sysctl 8
and
.Xr ioctl 2
interfaces as well as the
.Xr devd 8
event notification interface.
.Sh IOCTLS
Every ioctl for the
.Nm
driver takes a single integer value for the battery unit
number as an argument,
and returns a specific structure for each request.
A special unit number
.Dv ACPI_BATTERY_ALL_UNITS
specifies all of the attached units
and reports accumulated information.
.Bl -tag -width indent
.It Dv ACPIIO_BATT_GET_UNITS Vt int
Returns the number of battery units in the system.
The unit number argument will be ignored.
.It Dv ACPIIO_BATT_GET_BATTINFO Vt struct acpi_battinfo
Returns the following:
.Bl -tag -width indent
.It Va cap
Battery capacity in percent,
.It Va min
Remaining battery life in minutes,
.It Va state
Current status of the battery encoded in the following:
.Bl -tag -width indent
.It Dv ACPI_BATT_STAT_DISCHARG Pq 0x0001
Battery is discharging,
.It Dv ACPI_BATT_STAT_CHARGING Pq 0x0002
Battery is being charged, or
.It Dv ACPI_BATT_STAT_CRITICAL Pq 0x0004
Remaining battery life is critically low.
.El
.Pp
Note that the status bits of each battery will be
consolidated when
.Dv ACPI_BATTERY_ALL_UNITS
is specified.
.It Va rate
Current battery discharging rate in mW.
.Li -1
means not discharging right now.
.El
.It Dv ACPIIO_BATT_GET_BIX Vt struct acpi_bix
Returns battery information given by the ACPI
.Li _BIX Pq Battery Information
object,
which is the static portion of the Control Method
Battery information.
In the case of a Smart Battery attached to
SMBus or a Control Method Battery with a
.Li _BIF
object,
this ioctl will build a
.Vt struct acpi_bix
structure based on the obtained information
and return it.
.Bl -tag -width indent
.It Va rev
Revision number of the object.
There are the following well-known values:
.Bl -tag -width indent
.It Dv ACPI_BIX_REV_0 Pq 0x0000
A
.Li _BIX
object in ACPI 4.0.
.It Dv ACPI_BIX_REV_1 Pq 0x0001
A
.Li _BIX
object in ACPI 6.0.
.It Dv ACPI_BIX_REV_BIF Pq 0xffff
A
.Li _BIX
object built from the
.Li _BIF
object found on the system.
.El
.Pp
Note that this field should be checked by using
.Fn ACPI_BIX_REV_MIN_CHECK var rev
macro when checking the minimum revision number.
.It Va units
Indicates the units used by the battery to report its
capacity and charge rate encoded in the following:
.Bl -tag -width indent
.It ACPI_BIX_UNITS_MW Pq 0x00000000
in mW
.Pq power
.It ACPI_BIX_UNITS_MA Pq 0x00000001
in mA
.Pq current
.El
.Pp
Note that capacity is expressed in mWh or mAh,
and rate is expressed in mW or mA,
respectively.
.It Va dcap
The Battery's design capacity,
which is the nominal capacity of a new battery.
This is expressed as power or current depending on
the value of
.Va units .
.It Va lfcap
Predicted battery capacity when fully charged.
Typically this will decrease every charging cycle.
.It btech
Battery technology:
.Bl -tag -width indent
.It 0x00000000 Primary cell Pq non-rechargable
.It 0x00000001 Secondary cell Pq rechargable
.El
.It Va dvol
Design voltage in mV,
which is the nominal voltage of a new battery.
.It Va wcap
Design capacity of warning.
When a discharging battery device reaches this capacity,
notification is sent to the system.
.It Va lcap
Design capacity of low.
.It Va cycles
.Pq rev 0 or newer
The number of cycles the battery has experienced.
A cycle means an amount of discharge occurred which was
approximately equal to the value of Design Capacity.
.It Va accuracy
.Pq rev 0 or newer
The accuracy of the battery capacity measurement,
in thousandth of a percent.
.It Va stmax
.Pq rev 0 or newer
The Maximum Sampling Time of the battery in
milliseconds.
This is the maximum duration between two consecutive
measurements of the battery's capacities specified in
.Li _BST .
If two succeeding readings of
.Li _BST
beyond this duration occur,
two different results can be returned.
.It Va stmin
.Pq rev 0 or newer
The Minimum Sampling Time of the battery in
milliseconds.
.It Va aimax
.Pq rev 0 or newer
The Maximum Average Interval of the battery in
milliseconds.
This is the length of time within which the battery
averages the capacity measurements specified in
.Li _BST .
The Sampling Time specifies the frequency of measurements,
and the Average Interval specifies the width of the time
window of every measurement.
.It Va aimin
.Pq rev 0 or newer
The Minimum Average Interval of the battery in
milliseconds.
.It Va gra1
Battery capacity granularity between
.Va low
and
.Va warning .
This is expressed as power or current depending on
the value of
.Va units .
.It Va gra2
Battery capacity granularity between
.Va warning
and
.Va full .
This is expressed as power or current depending on
the value of
.Va units .
.It Va model
Model number of the battery as a string.
.It Va serial
Serial number of the battery as a string.
.It Va type
Type identifier of the battery as a string.
.It Va oeminfo
OEM-specific information of the battery as a string.
.It Va scap
.Pq rev 1 or newer
Battery swapping capability encoded in the following:
.Bl -tag -width indent
.It ACPI_BIX_SCAP_NO Pq 0x00000000
Non-swappable
.It ACPI_BIX_SCAP_COLD Pq 0x00000001
Cold-swappable
.It ACPI_BIX_SCAP_HOT Pq 0x00000010
Hot-swappable
.El
.El
.It Dv ACPIIO_BATT_GET_BIF Vt struct acpi_bif
.Pq deprecated
Returns battery information given by the ACPI
.Li _BIF Pq Battery Information
object,
which was deprecated in ACPI 4.0 specification.
The data structure is a subset of
.Vt struct acpi_bix .
.Pp
Note that this ioctl will built a
.Vt struct acpi_bif
structure based on the obtained information
even if this object is not available and a
.Li _BIX
object is found.
.It ACPIIO_BATT_GET_BST Vt struct acpi_bst
Returns battery information given by the ACPI
.Li _BST Pq Battery Status
object,
which is the present battery status.
In the case of a Smart Battery attached to SMBus,
this ioctl will build a
.Vt struct acpi_bst
structure based on the obtained information
and return it.
.Bl -tag -width indent
.It Va state
Battery state.
The value is encoded in the same way as
.Va state
of
.Vt struct acpi_battinfo .
.It Va rate
Battery present rate of charging or discharging.
The unit of the value depends on
.Va unit
of
.Vt struct acpi_bif .
.It Va cap
Battery remaining capacity.
The unit of this value depends on
.Va unit
of
.Vt struct acpi_bif .
.It Va volt
Battery present voltage.
.El
.El
.Sh SYSCTL VARIABLES
The following
.Xr sysctl 8
variables export battery status.
Note that they are accumulated status of all of the
connected batteries:
.Bl -tag -width indent
.It Va hw.acpi.battery.info_expire
Information cache expiration time in seconds.
The battery information obtained by
.Li _BIX
or
.Li _BIF
object will be stored and reused for successive
read access to this MIB within the specified period.
.It Va hw.acpi.battery.units
Number of battery units in the system.
.It Va hw.acpi.battery.state
Current battery charging status.
This is same as
.Va state
of
.Vt struct acpi_battinfo .
.It Va hw.acpi.battery.rate
Current battery discharging rate in mW.
.It Va hw.acpi.battery.time
Remaining battery life in minutes.
If the battery is not discharging,
the value shows
.Li -1 .
.It Va hw.acpi.battery.life
Battery capacity in percent.
.El
.Sh EVENT NOTIFICATIONS
Battery-related event notifications are sent
to the userland via the
.Xr devd 8
interface.
See
.Pa /etc/devd.conf
and
.Xr devd.conf 5
for more details.
Note that notifications are supported only by
the Control Method Battery.
.Pp
The
.Nm
driver sends events with the following attributes:
.Pp
.Bl -tag -width "subsystem" -compact
.It system
.Li ACPI
.It subsystem
.Li CMBAT
.It type
The fully qualified battery object path as in the ASL.
.It notify
An integer designating the event:
.Pp
.Bl -tag -width indent -compact
.It Li 0x80
Battery status was changed.
.It Li 0x81
Battery information was changed.
.El
.El
.Sh SEE ALSO
.Xr acpi 4 ,
.Xr acpiconf 8
.Sh AUTHORS
.An -nosplit
.An Nate Lawson Aq Mt njl@FreeBSD.org ,
.An Munehiro Matsuda ,
.An Takanori Watanabe Aq Mt takawata@FreeBSD.org ,
.An Mitsuru IWASAKI Aq Mt iwasaki@FreeBSD.org ,
.An Hans Petter Selasky Aq Mt hselasky@FreeBSD.org ,
and
.An Hiroki Sato Aq Mt hrs@FreeBSD.org .
.Pp
This manual page was written by
.An Takanori Watanabe Aq Mt takawata@FreeBSD.org
and
.An Hiroki Sato Aq Mt hrs@FreeBSD.org .
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