battery: Add the internal Battery API

This patch adds an API for internal BlueZ code to expose battery
information to org.bluez.Battery1 interface. The motivation behind this
is that there is going to be other places than GATT BAS handler that
exposes battery information, for example internal plugins and the
BatteryProvider1 D-Bus API for external clients.

Reviewed-by: Daniel Winkler <danielwinkler@google.com>

1 files changed, 191 insertions, 0 deletions

diff --git a/src/battery.c b/src/battery.c
new file mode 100644
index 000000000..87a6b91fb
--- /dev/null
+++ b/src/battery.c
@@ -0,0 +1,191 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *
+ *  BlueZ - Bluetooth protocol stack for Linux
+ *
+ *  Copyright (C) 2020  Google LLC
+ *
+ *
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#define _GNU_SOURCE
+#include <stdbool.h>
+#include <stdint.h>
+#include <glib.h>
+
+#include "gdbus/gdbus.h"
+#include "lib/bluetooth.h"
+#include "src/shared/queue.h"
+#include "src/shared/util.h"
+#include "battery.h"
+#include "dbus-common.h"
+#include "adapter.h"
+#include "log.h"
+
+#define BATTERY_INTERFACE "org.bluez.Battery1"
+
+#define BATTERY_MAX_PERCENTAGE 100
+
+struct btd_battery {
+	char *path; /* D-Bus object path, owns pointer */
+	uint8_t percentage; /* valid between 0 to 100 inclusively */
+};
+
+static struct queue *batteries = NULL;
+
+static void battery_add(struct btd_battery *battery)
+{
+	if (!batteries)
+		batteries = queue_new();
+
+	queue_push_head(batteries, battery);
+}
+
+static void battery_remove(struct btd_battery *battery)
+{
+	queue_remove(batteries, battery);
+	if (queue_isempty(batteries)) {
+		queue_destroy(batteries, NULL);
+		batteries = NULL;
+	}
+}
+
+static bool match_path(const void *data, const void *user_data)
+{
+	const struct btd_battery *battery = data;
+	const char *path = user_data;
+
+	return g_strcmp0(battery->path, path) == 0;
+}
+
+static struct btd_battery *battery_new(const char *path)
+{
+	struct btd_battery *battery;
+
+	battery = new0(struct btd_battery, 1);
+	battery->path = g_strdup(path);
+	battery->percentage = UINT8_MAX;
+
+	return battery;
+}
+
+static void battery_free(struct btd_battery *battery)
+{
+	if (battery->path)
+		g_free(battery->path);
+
+	free(battery);
+}
+
+static gboolean property_percentage_get(const GDBusPropertyTable *property,
+					DBusMessageIter *iter, void *data)
+{
+	struct btd_battery *battery = data;
+
+	dbus_message_iter_append_basic(iter, DBUS_TYPE_BYTE,
+				       &battery->percentage);
+
+	return TRUE;
+}
+
+static gboolean property_percentage_exists(const GDBusPropertyTable *property,
+					   void *data)
+{
+	struct btd_battery *battery = data;
+
+	return battery->percentage <= BATTERY_MAX_PERCENTAGE;
+}
+
+static const GDBusPropertyTable battery_properties[] = {
+	{ "Percentage", "y", property_percentage_get, NULL,
+	  property_percentage_exists },
+	{}
+};
+
+struct btd_battery *btd_battery_register(const char *path)
+{
+	struct btd_battery *battery;
+
+	DBG("path = %s", path);
+
+	if (queue_find(batteries, match_path, path)) {
+		error("error registering battery: path exists");
+		return NULL;
+	}
+
+	if (!g_str_has_prefix(path, "/")) {
+		error("error registering battery: invalid D-Bus object path");
+		return NULL;
+	}
+
+	battery = battery_new(path);
+	battery_add(battery);
+
+	if (!g_dbus_register_interface(btd_get_dbus_connection(), battery->path,
+				       BATTERY_INTERFACE, NULL, NULL,
+				       battery_properties, battery, NULL)) {
+		error("error registering D-Bus interface for %s",
+		      battery->path);
+
+		battery_remove(battery);
+		battery_free(battery);
+
+		return NULL;
+	}
+
+	DBG("registered Battery object: %s", battery->path);
+
+	return battery;
+}
+
+bool btd_battery_unregister(struct btd_battery *battery)
+{
+	DBG("path = %s", battery->path);
+
+	if (!queue_find(batteries, NULL, battery)) {
+		error("error unregistering battery: "
+		      "battery %s is not registered",
+		      battery->path);
+		return false;
+	}
+
+	if (!g_dbus_unregister_interface(btd_get_dbus_connection(),
+					 battery->path, BATTERY_INTERFACE)) {
+		error("error unregistering battery %s from D-Bus interface",
+		      battery->path);
+		return false;
+	}
+
+	battery_remove(battery);
+	battery_free(battery);
+
+	return true;
+}
+
+bool btd_battery_update(struct btd_battery *battery, uint8_t percentage)
+{
+	DBG("path = %s", battery->path);
+
+	if (!queue_find(batteries, NULL, battery)) {
+		error("error updating battery: battery is not registered");
+		return false;
+	}
+
+	if (percentage > BATTERY_MAX_PERCENTAGE) {
+		error("error updating battery: percentage is not valid");
+		return false;
+	}
+
+	if (battery->percentage == percentage)
+		return true;
+
+	battery->percentage = percentage;
+	g_dbus_emit_property_changed(btd_get_dbus_connection(), battery->path,
+				     BATTERY_INTERFACE, "Percentage");
+
+	return true;
+}