battery: Add the battery hooking API

This is a patch that implements a generic hooking API for the
generic ACPI battery driver.

With this new generic API, drivers can expose platform specific
behaviour via sysfs attributes in /sys/class/power_supply/BATn/
in a generic way.

A perfect example of the need for this API are Lenovo ThinkPads.

Lenovo ThinkPads have a ACPI extension that allows the setting of
start and stop charge thresholds in the EC and battery firmware
via ACPI. The thinkpad_acpi module can use this API to expose
sysfs attributes that it controls inside the ACPI battery driver
sysfs tree, under /sys/class/power_supply/BATN/.

The file drivers/acpi/battery.h has been moved to
include/acpi/battery.h and the includes inside ac.c, sbs.c, and
battery.c have been adjusted to reflect that.

When drivers hooks into the API, the API calls add_battery() for
each battery in the system that passes it a acpi_battery
struct. Then, the drivers can use device_create_file() to create
new sysfs attributes with that struct and identify the batteries
for per-battery attributes.

Signed-off-by: Ognjen Galic <smclt30p@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/include/acpi/battery.h b/include/acpi/battery.h
new file mode 100644
index 000000000000..5d8f5d910c82
--- /dev/null
+++ b/include/acpi/battery.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ACPI_BATTERY_H
+#define __ACPI_BATTERY_H
+
+#define ACPI_BATTERY_CLASS "battery"
+
+#define ACPI_BATTERY_NOTIFY_STATUS	0x80
+#define ACPI_BATTERY_NOTIFY_INFO	0x81
+#define ACPI_BATTERY_NOTIFY_THRESHOLD   0x82
+
+struct acpi_battery_hook {
+	const char *name;
+	int (*add_battery)(struct power_supply *battery);
+	int (*remove_battery)(struct power_supply *battery);
+	struct list_head list;
+};
+
+void battery_hook_register(struct acpi_battery_hook *hook);
+void battery_hook_unregister(struct acpi_battery_hook *hook);
+
+#endif