定義acpi battery 結構體保存global的一些參數
struct acpi_battery {
struct mutex lock;
struct mutex sysfs_lock;
struct power_supply *bat;
struct power_supply_desc bat_desc;
struct acpi_device *device;
struct notifier_block pm_nb;
struct list_head list;
unsigned long update_time;
int revision;
int rate_now;
int capacity_now;
int voltage_now;
int design_capacity;
int full_charge_capacity;
int technology;
int design_voltage;
int design_capacity_warning;
int design_capacity_low;
int cycle_count;
int measurement_accuracy;
int max_sampling_time;
int min_sampling_time;
int max_averaging_interval;
int min_averaging_interval;
int capacity_granularity_1;
int capacity_granularity_2;
int alarm;
char model_number[32];
char serial_number[32];
char type[32];
char oem_info[32];
int state;
int power_unit;
unsigned long flags;
};
ACPI battery 結構體中很多的參數都有一個offset
/* --------------------------------------------------------------------------
Battery Management
-------------------------------------------------------------------------- */
struct acpi_offsets {
size_t offset; /* offset inside struct acpi_sbs_battery */
u8 mode; /* int or string? */
};
static const struct acpi_offsets state_offsets[] = {
{offsetof(struct acpi_battery, state), 0},
{offsetof(struct acpi_battery, rate_now), 0},
{offsetof(struct acpi_battery, capacity_now), 0},
{offsetof(struct acpi_battery, voltage_now), 0},
};
static const struct acpi_offsets info_offsets[] = {
{offsetof(struct acpi_battery, power_unit), 0},
{offsetof(struct acpi_battery, design_capacity), 0},
{offsetof(struct acpi_battery, full_charge_capacity), 0},
{offsetof(struct acpi_battery, technology), 0},
{offsetof(struct acpi_battery, design_voltage), 0},
{offsetof(struct acpi_battery, design_capacity_warning), 0},
{offsetof(struct acpi_battery, design_capacity_low), 0},
{offsetof(struct acpi_battery, capacity_granularity_1), 0},
{offsetof(struct acpi_battery, capacity_granularity_2), 0},
{offsetof(struct acpi_battery, model_number), 1},
{offsetof(struct acpi_battery, serial_number), 1},
{offsetof(struct acpi_battery, type), 1},
{offsetof(struct acpi_battery, oem_info), 1},
};
static const struct acpi_offsets extended_info_offsets[] = {
{offsetof(struct acpi_battery, revision), 0},
{offsetof(struct acpi_battery, power_unit), 0},
{offsetof(struct acpi_battery, design_capacity), 0},
{offsetof(struct acpi_battery, full_charge_capacity), 0},
{offsetof(struct acpi_battery, technology), 0},
{offsetof(struct acpi_battery, design_voltage), 0},
{offsetof(struct acpi_battery, design_capacity_warning), 0},
{offsetof(struct acpi_battery, design_capacity_low), 0},
{offsetof(struct acpi_battery, cycle_count), 0},
{offsetof(struct acpi_battery, measurement_accuracy), 0},
{offsetof(struct acpi_battery, max_sampling_time), 0},
{offsetof(struct acpi_battery, min_sampling_time), 0},
{offsetof(struct acpi_battery, max_averaging_interval), 0},
{offsetof(struct acpi_battery, min_averaging_interval), 0},
{offsetof(struct acpi_battery, capacity_granularity_1), 0},
{offsetof(struct acpi_battery, capacity_granularity_2), 0},
{offsetof(struct acpi_battery, model_number), 1},
{offsetof(struct acpi_battery, serial_number), 1},
{offsetof(struct acpi_battery, type), 1},
{offsetof(struct acpi_battery, oem_info), 1},
};
然後開始battery 參數的初始化流程
用acpi_evaluate_object 去call BIOS ACPI的_BIX 方法或者_BIF
在acpi的spec 中定義如下：
_BIF
Battery Information – returns a Control Method Battery information block.
Section 10.2.2.1
_BIX
Battery Information Extended – returns a Control Method Battery extended information block.
Section 10.2.2.2
10.2.2.2 _BIX (Battery Information Extended)
The _BIX object returns the static portion of the Control Method Battery information. This information remains constant until the battery is changed. The _BIX object returns all information available via the _BIF object plus additional battery information. The _BIF object is deprecated in lieu of _BIX in ACPI 4.0.
Arguments:
None
Return Value:
A Package containing the battery information as described below
Return Value Information:
_BIX returns a package in the format below
Package {
// ASCIIZ is ASCII character string terminated with a 0x00.
Revision //Integer
Power Unit //Integer (DWORD)
Design Capacity //Integer (DWORD)
Last Full Charge Capacity //Integer (DWORD)
Battery Technology //Integer (DWORD)
Design Voltage //Integer (DWORD)
Design Capacity of Warning //Integer (DWORD)
Design Capacity of Low //Integer (DWORD)
Cycle Count //Integer (DWORD)
Measurement Accuracy //Integer (DWORD)
Max Sampling Time //Integer (DWORD)
Min Sampling Time //Integer (DWORD)
Max Averaging Interval //Integer (DWORD)
Min Averaging Interval //Integer (DWORD)
Battery Capacity Granularity 1 //Integer (DWORD)
Battery Capacity Granularity 2 //Integer (DWORD)
Model Number //String (ASCIIZ)
Serial Number //String (ASCIIZ)
Battery Type //String (ASCIIZ)
OEM Information //String (ASCIIZ)
Battery Swapping Capability //Integer (DWORD)
}
Kernel 通過ACPi方法 獲取了battery的全部參數，然後填充這些參數到kernel的driver中，之後直接查詢kernel的參數，而不是去掉ACPI 去查找.
常見的ACPI 操作。
static int acpi_battery_get_info(struct acpi_battery *battery)
{
const int xinfo = test_bit(ACPI_BATTERY_XINFO_PRESENT, &battery->flags);
int use_bix;
int result = -ENODEV;
if (!acpi_battery_present(battery))
return 0;
for (use_bix = xinfo ? 1 : 0; use_bix >= 0; use_bix--) {
struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
acpi_status status = AE_ERROR;
mutex_lock(&battery->lock);
status = acpi_evaluate_object(battery->device->handle,
use_bix ? "_BIX":"_BIF",
NULL, &buffer);
mutex_unlock(&battery->lock);
if (ACPI_FAILURE(status)) {
ACPI_EXCEPTION((AE_INFO, status, "Evaluating %s",
use_bix ? "_BIX":"_BIF"));
} else {
result = extract_battery_info(use_bix,
battery,
&buffer);
kfree(buffer.pointer);
break;
}
}
if (!result && !use_bix && xinfo)
pr_warn(FW_BUG "The _BIX method is broken, using _BIF.\n");
return result;
}
通過ACPI 方法從BIOS 獲取全部電池相關的參數
status = acpi_evaluate_object(battery->device->handle,
use_bix ? “_BIX”:"_BIF",
NULL, &buffer);
然後提取相關的Battery info 填充acpi_battery 結構體內各個battery 參數
result = extract_battery_info(use_bix,
battery,
&buffer);
static int extract_battery_info(const int use_bix,
struct acpi_battery *battery,
const struct acpi_buffer *buffer)
{
int result = -EFAULT;
if (use_bix && battery_bix_broken_package)
result = extract_package(battery, buffer->pointer,
extended_info_offsets + 1,
ARRAY_SIZE(extended_info_offsets) - 1);
else if (use_bix)
result = extract_package(battery, buffer->pointer,
extended_info_offsets,
ARRAY_SIZE(extended_info_offsets));
else
result = extract_package(battery, buffer->pointer,
info_offsets, ARRAY_SIZE(info_offsets));
if (test_bit(ACPI_BATTERY_QUIRK_PERCENTAGE_CAPACITY, &battery->flags))
battery->full_charge_capacity = battery->design_capacity;
if (test_bit(ACPI_BATTERY_QUIRK_THINKPAD_MAH, &battery->flags) &&
battery->power_unit && battery->design_voltage) {
battery->design_capacity = battery->design_capacity *
10000 / battery->design_voltage;
battery->full_charge_capacity = battery->full_charge_capacity *
10000 / battery->design_voltage;
battery->design_capacity_warning =
battery->design_capacity_warning *
10000 / battery->design_voltage;
/* Curiously, design_capacity_low, unlike the rest of them,
is correct. */
/* capacity_granularity_* equal 1 on the systems tested, so
it's impossible to tell if they would need an adjustment
or not if their values were higher. */
}
if (test_bit(ACPI_BATTERY_QUIRK_DEGRADED_FULL_CHARGE, &battery->flags) &&
battery->capacity_now > battery->full_charge_capacity)
battery->capacity_now = battery->full_charge_capacity;
return result;
}