[PATCH v2 3/4] hw/acpi: Introduce the QEMU AC adapter

[Leonid Bloch <lb.workbox@gmail.com>]

The AC adapter device communicates AC power state to the guest via ACPI.
It supports two modes of operation:

1. QMP control mode (default): AC adapter state is controlled
   programmatically via QMP commands, ensuring deterministic behavior.

2. Host mirroring mode (optional): The device reflects the host's AC
   adapter state from sysfs. Probing occurs on guest ACPI requests and
   at timed intervals. State changes trigger ACPI notifications.

Properties:
- 'use-qmp': Enable QMP control mode (default: true)
- 'enable-sysfs': Enable host AC adapter mirroring (default: false)
- 'probe_interval': Probe interval in ms for sysfs mode (default: 2000)
- 'sysfs_path': Override default sysfs path /sys/class/power_supply/

The device implements the ACPI_DEV_AML_IF interface to generate its
own AML code, placing the ADP0 device directly under \_SB scope.

QMP commands:
- ac-adapter-set-state: Set AC adapter connection state
- query-ac-adapter: Query current AC adapter state

Signed-off-by: Leonid Bloch <lb.workbox@gmail.com>
---
 MAINTAINERS                          |   6 +
 docs/specs/acad.rst                  | 195 ++++++++++++
 docs/specs/index.rst                 |   1 +
 hw/acpi/Kconfig                      |   4 +
 hw/acpi/acad.c                       | 447 +++++++++++++++++++++++++++
 hw/acpi/meson.build                  |   1 +
 hw/acpi/trace-events                 |   5 +
 hw/i386/Kconfig                      |   1 +
 include/hw/acpi/acad.h               |  27 ++
 include/hw/acpi/acpi_dev_interface.h |   1 +
 qapi/acpi.json                       |  49 +++
 11 files changed, 737 insertions(+)
 create mode 100644 docs/specs/acad.rst
 create mode 100644 hw/acpi/acad.c
 create mode 100644 include/hw/acpi/acad.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 51af9b7366..612efcb686 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2927,6 +2927,12 @@ S: Maintained
 F: hw/acpi/battery.*
 F: docs/specs/battery.rst
 
+AC Adapter
+M: Leonid Bloch <lb.workbox@gmail.com>
+S: Maintained
+F: hw/acpi/acad.*
+F: docs/specs/acad.rst
+
 Subsystems
 ----------
 Overall Audio backends
diff --git a/docs/specs/acad.rst b/docs/specs/acad.rst
new file mode 100644
index 0000000000..73d5501b8f
--- /dev/null
+++ b/docs/specs/acad.rst
@@ -0,0 +1,195 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+=================
+AC Adapter Device
+=================
+
+The AC adapter device provides AC power state information to the guest. It
+supports two operating modes:
+
+1. **QMP Control Mode** (default): AC adapter state is controlled via QMP
+   commands, providing deterministic control for testing and migration safety.
+2. **Sysfs Mode**: AC adapter state mirrors the host's physical AC adapter,
+   useful for desktop virtualization where the guest should see the host's
+   power state.
+
+Configuration
+-------------
+
+The AC adapter device is created as an ISA device using ``-device acad``.
+
+Operating Modes
+~~~~~~~~~~~~~~~
+
+**QMP Control Mode** (``use-qmp=true``, default)
+  AC adapter state is controlled via QMP commands. This mode is recommended for:
+
+  * Production environments requiring migration support
+  * Testing with predictable power states
+  * Environments without host AC adapter access
+  * Security-sensitive deployments
+
+**Sysfs Mode** (``enable-sysfs=true``)
+  AC adapter mirrors the host's physical AC adapter. This mode is useful for:
+
+  * Desktop virtualization on laptops
+  * Development and testing with real AC adapter behavior
+
+  Note: Sysfs mode reads host files and runs timers, which may impact
+  security and migration. Use with caution in production.
+
+Properties
+~~~~~~~~~~
+
+``ioport`` (default: 0x53c)
+  I/O port base address for the AC adapter device register.
+
+``use-qmp`` (default: true)
+  Enable QMP control mode. When true, AC adapter state is controlled via
+  QMP commands. Cannot be used together with ``enable-sysfs=true``.
+
+``enable-sysfs`` (default: false)
+  Enable sysfs mode to mirror the host's AC adapter. Cannot be used together
+  with ``use-qmp=true``.
+
+``probe_interval`` (default: 2000)
+  Time interval between periodic probes in milliseconds (sysfs mode only).
+  A zero value disables the periodic probes, and makes the AC adapter state
+  updates occur on guest requests only.
+
+``sysfs_path`` (default: auto-detected)
+  Path to the host's AC adapter sysfs directory (sysfs mode only). By default,
+  the device auto-detects the first AC adapter of type "Mains" in
+  ``/sys/class/power_supply/``. Use this property to specify a different
+  AC adapter, or to provide a custom path for testing purposes.
+
+Host AC Adapter Detection
+-------------------------
+
+The host's AC adapter information is taken from the sysfs AC adapter
+data, located in::
+
+    /sys/class/power_supply/[device of type "Mains"]
+
+The device automatically scans for the first AC adapter with:
+
+- A ``type`` file containing "Mains"
+- An ``online`` file that can be read
+
+If the sysfs path differs, a different AC adapter needs to be probed,
+or even if a "fake" host AC adapter is to be provided, the ``sysfs_path``
+property allows overriding the default detection.
+
+ACPI Interface
+--------------
+
+The AC adapter device is exposed to the guest as an ACPI device with:
+
+- **HID**: ``ACPI0003`` (AC Adapter)
+- **Device Path**: ``\_SB.ADP0``
+- **Notification Values**:
+
+  - ``0x80``: Status change (connected/disconnected)
+
+ACPI Methods
+~~~~~~~~~~~~
+
+``_PSR`` (Power Source)
+  Returns the current AC adapter state (0 = offline, 1 = online).
+
+``_PCL`` (Power Consumer List)
+  Returns the list of devices powered by this adapter.
+
+``_PIF`` (Power Source Information)
+  Returns static information about the power source including model number,
+  serial number, and OEM information.
+
+I/O Interface
+-------------
+
+The device uses a single I/O port register:
+
+- **Port**: ``ioport`` property value (default 0x53c)
+- **Size**: 1 byte
+- **Access**: Read-only
+
+Register Layout
+~~~~~~~~~~~~~~~
+
+**PWRS** (offset 0x00, 1 byte)
+  Current AC adapter state:
+
+  - ``0x00``: AC adapter offline (unplugged)
+  - ``0x01``: AC adapter online (plugged in)
+
+QMP Commands
+------------
+
+When using QMP control mode (default), the following commands are available:
+
+``ac-adapter-set-state``
+  Set the AC adapter connection state.
+
+  * ``connected``: Whether the AC adapter is connected (boolean)
+
+  Example::
+
+    -> { "execute": "ac-adapter-set-state",
+         "arguments": { "connected": true }}
+    <- { "return": {} }
+
+``query-ac-adapter``
+  Query the current AC adapter state.
+
+  Example::
+
+    -> { "execute": "query-ac-adapter" }
+    <- { "return": { "connected": true }}
+
+Examples
+--------
+
+QMP control mode (default - recommended)::
+
+  # Start with QMP control
+  qemu-system-x86_64 -device acad -qmp tcp:localhost:4444,server,wait=off
+
+  # From another terminal, set AC adapter state via QMP:
+  echo '{"execute":"qmp_capabilities"}
+        {"execute":"ac-adapter-set-state",
+         "arguments":{"connected":true}}' | \
+  nc -N localhost 4444
+
+Sysfs mode (mirror host AC adapter)::
+
+  # Enable sysfs mode to mirror host AC adapter
+  qemu-system-x86_64 -device acad,use-qmp=false,enable-sysfs=true
+
+  # Custom probe interval (5 seconds)
+  qemu-system-x86_64 -device acad,use-qmp=false,enable-sysfs=true,probe_interval=5000
+
+  # Specific AC adapter path
+  qemu-system-x86_64 -device acad,use-qmp=false,enable-sysfs=true,sysfs_path=/sys/class/power_supply/ADP1
+
+Testing with fake AC adapter::
+
+  # Create fake AC adapter files for testing
+  mkdir -p /tmp/fake_ac
+  echo "Mains" > /tmp/fake_ac/type
+  echo "1" > /tmp/fake_ac/online          # 1 = connected, 0 = disconnected
+
+  # Use fake AC adapter in sysfs mode
+  qemu-system-x86_64 -device acad,use-qmp=false,enable-sysfs=true,sysfs_path=/tmp/fake_ac
+
+  # Update AC adapter state while VM is running (from another terminal)
+  echo "0" > /tmp/fake_ac/online          # Disconnect AC adapter
+  echo "1" > /tmp/fake_ac/online          # Reconnect AC adapter
+
+Combined with battery device::
+
+  # QMP mode (recommended)
+  qemu-system-x86_64 -device battery -device acad
+
+  # Sysfs mode (desktop virtualization)
+  qemu-system-x86_64 -device battery,use-qmp=false,enable-sysfs=true \
+                     -device acad,use-qmp=false,enable-sysfs=true
diff --git a/docs/specs/index.rst b/docs/specs/index.rst
index 616e8228cc..e144afcd90 100644
--- a/docs/specs/index.rst
+++ b/docs/specs/index.rst
@@ -22,6 +22,7 @@ guest hardware that is specific to QEMU.
    acpi_pci_hotplug
    acpi_nvdimm
    acpi_erst
+   acad
    battery
    sev-guest-firmware
    fw_cfg
diff --git a/hw/acpi/Kconfig b/hw/acpi/Kconfig
index 64403378bd..9d28c3addf 100644
--- a/hw/acpi/Kconfig
+++ b/hw/acpi/Kconfig
@@ -69,6 +69,10 @@ config ACPI_VIOT
     bool
     depends on ACPI
 
+config AC_ADAPTER
+    bool
+    depends on ACPI
+
 config ACPI_HW_REDUCED
     bool
     select ACPI
diff --git a/hw/acpi/acad.c b/hw/acpi/acad.c
new file mode 100644
index 0000000000..699198c194
--- /dev/null
+++ b/hw/acpi/acad.c
@@ -0,0 +1,447 @@
+/*
+ * QEMU emulated AC adapter device.
+ *
+ * Copyright (c) 2019 Janus Technologies, Inc. (http://janustech.com)
+ *
+ * Authors:
+ *     Leonid Bloch <lb.workbox@gmail.com>
+ *     Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
+ *     Dmitry Fleytman <dmitry.fleytman@gmail.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "trace.h"
+#include "hw/isa/isa.h"
+#include "hw/acpi/acpi.h"
+#include "hw/nvram/fw_cfg.h"
+#include "qapi/error.h"
+#include "qemu/error-report.h"
+#include "hw/qdev-properties.h"
+#include "migration/vmstate.h"
+#include "hw/acpi/acpi_aml_interface.h"
+#include "qapi/qapi-commands-acpi.h"
+
+#include "hw/acpi/acad.h"
+
+#define AC_ADAPTER_DEVICE(obj) OBJECT_CHECK(ACADState, (obj), \
+                                            TYPE_AC_ADAPTER)
+
+#define AC_STA_ADDR               0
+
+#define SYSFS_PATH                "/sys/class/power_supply"
+#define AC_ADAPTER_TYPE           "Mains"
+#define MAX_ALLOWED_TYPE_LENGTH   16
+
+enum {
+    AC_ADAPTER_OFFLINE = 0,
+    AC_ADAPTER_ONLINE = 1,
+};
+
+typedef struct ACADState {
+    ISADevice dev;
+    MemoryRegion io;
+    uint16_t ioport;
+    uint8_t state;
+    bool use_qmp_control;
+    bool qmp_connected;
+    bool enable_sysfs;
+
+    QEMUTimer *probe_state_timer;
+    uint64_t probe_state_interval;
+
+    char *acad_path;
+} ACADState;
+
+static const char *online_file = "online";
+static const char *type_file = "type";
+
+static inline bool acad_file_accessible(char *path, const char *file)
+{
+    char full_path[PATH_MAX];
+    int path_len;
+
+    path_len = snprintf(full_path, PATH_MAX, "%s/%s", path, file);
+    if (path_len < 0 || path_len >= PATH_MAX) {
+        return false;
+    }
+
+    if (access(full_path, R_OK) == 0) {
+        return true;
+    }
+    return false;
+}
+
+static void acad_get_state(ACADState *s)
+{
+    char file_path[PATH_MAX];
+    int path_len;
+    uint8_t val;
+    FILE *ff;
+
+    path_len = snprintf(file_path, PATH_MAX, "%s/%s", s->acad_path,
+                        online_file);
+    if (path_len < 0 || path_len >= PATH_MAX) {
+        warn_report("Could not read the AC adapter state.");
+        return;
+    }
+
+    ff = fopen(file_path, "r");
+    if (ff == NULL) {
+        warn_report("Could not read the AC adapter state.");
+        return;
+    }
+
+    if (!fscanf(ff, "%hhu", &val)) {
+        warn_report("AC adapter state unreadable.");
+    } else {
+        switch (val) {
+        case AC_ADAPTER_OFFLINE:
+        case AC_ADAPTER_ONLINE:
+            s->state = val;
+            break;
+        default:
+            warn_report("AC adapter state undetermined.");
+        }
+    }
+    fclose(ff);
+}
+
+static void acad_get_dynamic_status(ACADState *s)
+{
+    if (s->use_qmp_control) {
+        s->state = s->qmp_connected ? AC_ADAPTER_ONLINE : AC_ADAPTER_OFFLINE;
+    } else if (s->enable_sysfs) {
+        acad_get_state(s);
+    } else {
+        s->state = AC_ADAPTER_OFFLINE;
+    }
+
+    trace_acad_get_dynamic_status(s->state);
+}
+
+static void acad_probe_state(void *opaque)
+{
+    ACADState *s = opaque;
+
+    uint8_t state_before = s->state;
+
+    acad_get_dynamic_status(s);
+
+    if (state_before != s->state) {
+        Object *obj = object_resolve_path_type("", TYPE_ACPI_DEVICE_IF, NULL);
+        acpi_send_event(DEVICE(obj), ACPI_AC_ADAPTER_CHANGE_STATUS);
+    }
+    timer_mod(s->probe_state_timer, qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) +
+              s->probe_state_interval);
+}
+
+static void acad_probe_state_timer_init(ACADState *s)
+{
+    if (s->enable_sysfs && s->probe_state_interval > 0) {
+        s->probe_state_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
+                                            acad_probe_state, s);
+        timer_mod(s->probe_state_timer, qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) +
+                  s->probe_state_interval);
+    }
+}
+
+static bool acad_verify_sysfs(ACADState *s, char *path)
+{
+    FILE *ff;
+    char type_path[PATH_MAX];
+    int path_len;
+    char val[MAX_ALLOWED_TYPE_LENGTH];
+
+    path_len = snprintf(type_path, PATH_MAX, "%s/%s", path, type_file);
+    if (path_len < 0 || path_len >= PATH_MAX) {
+        return false;
+    }
+
+    ff = fopen(type_path, "r");
+    if (ff == NULL) {
+        return false;
+    }
+
+    if (fgets(val, MAX_ALLOWED_TYPE_LENGTH, ff) == NULL) {
+        fclose(ff);
+        return false;
+    } else {
+        val[strcspn(val, "\n")] = 0;
+        if (strncmp(val, AC_ADAPTER_TYPE, MAX_ALLOWED_TYPE_LENGTH)) {
+            fclose(ff);
+            return false;
+        }
+    }
+    fclose(ff);
+
+    return acad_file_accessible(path, online_file);
+}
+
+static bool get_acad_path(DeviceState *dev)
+{
+    ACADState *s = AC_ADAPTER_DEVICE(dev);
+    DIR *dir;
+    struct dirent *ent;
+    char bp[PATH_MAX];
+    int path_len;
+
+    if (s->acad_path) {
+        return acad_verify_sysfs(s, s->acad_path);
+    }
+
+    dir = opendir(SYSFS_PATH);
+    if (dir == NULL) {
+        return false;
+    }
+
+    ent = readdir(dir);
+    while (ent != NULL) {
+        if (ent->d_name[0] != '.') {
+            path_len = snprintf(bp, PATH_MAX, "%s/%s", SYSFS_PATH,
+                                ent->d_name);
+            if (path_len < 0 || path_len >= PATH_MAX) {
+                return false;
+            }
+            if (acad_verify_sysfs(s, bp)) {
+                qdev_prop_set_string(dev, AC_ADAPTER_PATH_PROP, bp);
+                closedir(dir);
+                return true;
+            }
+        }
+        ent = readdir(dir);
+    }
+    closedir(dir);
+
+    return false;
+}
+
+static void acad_realize(DeviceState *dev, Error **errp)
+{
+    ISADevice *d = ISA_DEVICE(dev);
+    ACADState *s = AC_ADAPTER_DEVICE(dev);
+    FWCfgState *fw_cfg = fw_cfg_find();
+    uint16_t *acad_port;
+    char err_details[32] = {};
+
+    trace_acad_realize();
+
+    if (s->use_qmp_control && s->enable_sysfs) {
+        error_setg(errp, "Cannot enable both QMP control and sysfs mode");
+        return;
+    }
+
+    if (s->enable_sysfs) {
+        if (!s->acad_path) {
+            strcpy(err_details, " Try using 'sysfs_path='");
+        }
+
+        if (!get_acad_path(dev)) {
+            error_setg(errp, "AC adapter sysfs path not found or unreadable.%s",
+                       err_details);
+            return;
+        }
+    }
+
+    isa_register_ioport(d, &s->io, s->ioport);
+
+    acad_probe_state_timer_init(s);
+
+    if (!fw_cfg) {
+        return;
+    }
+
+    acad_port = g_malloc(sizeof(*acad_port));
+    *acad_port = cpu_to_le16(s->ioport);
+    fw_cfg_add_file(fw_cfg, "etc/acad-port", acad_port,
+                    sizeof(*acad_port));
+}
+
+static const Property acad_device_properties[] = {
+    DEFINE_PROP_UINT16(AC_ADAPTER_IOPORT_PROP, ACADState, ioport, 0x53c),
+    DEFINE_PROP_BOOL("use-qmp", ACADState, use_qmp_control, true),
+    DEFINE_PROP_BOOL("enable-sysfs", ACADState, enable_sysfs, false),
+    DEFINE_PROP_UINT64(AC_ADAPTER_PROBE_STATE_INTERVAL, ACADState,
+                       probe_state_interval, 2000),
+    DEFINE_PROP_STRING(AC_ADAPTER_PATH_PROP, ACADState, acad_path),
+};
+
+static const VMStateDescription acad_vmstate = {
+    .name = "acad",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT16(ioport, ACADState),
+        VMSTATE_UINT64(probe_state_interval, ACADState),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static void build_acad_aml(AcpiDevAmlIf *adev, Aml *scope)
+{
+    Aml *dev, *field, *method, *pkg;
+    Aml *acad_state;
+    Aml *sb_scope;
+    ACADState *s = AC_ADAPTER_DEVICE(adev);
+
+    acad_state  = aml_local(0);
+
+    sb_scope = aml_scope("\\_SB");
+    dev = aml_device("ADP0");
+    aml_append(dev, aml_name_decl("_HID", aml_string("ACPI0003")));
+
+    aml_append(dev, aml_operation_region("ACST", AML_SYSTEM_IO,
+                                         aml_int(s->ioport),
+                                         AC_ADAPTER_LEN));
+    field = aml_field("ACST", AML_BYTE_ACC, AML_NOLOCK, AML_PRESERVE);
+    aml_append(field, aml_named_field("PWRS", 8));
+    aml_append(dev, field);
+
+    method = aml_method("_PSR", 0, AML_NOTSERIALIZED);
+    aml_append(method, aml_store(aml_name("PWRS"), acad_state));
+    aml_append(method, aml_return(acad_state));
+    aml_append(dev, method);
+
+    method = aml_method("_PCL", 0, AML_NOTSERIALIZED);
+    pkg = aml_package(1);
+    aml_append(pkg, aml_name("_SB"));
+    aml_append(method, aml_return(pkg));
+    aml_append(dev, method);
+
+    method = aml_method("_PIF", 0, AML_NOTSERIALIZED);
+    pkg = aml_package(6);
+    /* Power Source State */
+    aml_append(pkg, aml_int(0));  /* Non-redundant, non-shared */
+    /* Maximum Output Power */
+    aml_append(pkg, aml_int(AC_ADAPTER_VAL_UNKNOWN));
+    /* Maximum Input Power */
+    aml_append(pkg, aml_int(AC_ADAPTER_VAL_UNKNOWN));
+    /* Model Number */
+    aml_append(pkg, aml_string("QADP001"));
+    /* Serial Number */
+    aml_append(pkg, aml_string("SN00000"));
+    /* OEM Information */
+    aml_append(pkg, aml_string("QEMU"));
+    aml_append(method, aml_return(pkg));
+    aml_append(dev, method);
+
+    aml_append(sb_scope, dev);
+    aml_append(scope, sb_scope);
+
+    /* Status Change */
+    method = aml_method("\\_GPE._E0A", 0, AML_NOTSERIALIZED);
+    aml_append(method, aml_notify(aml_name("\\_SB.ADP0"), aml_int(0x80)));
+    aml_append(scope, method);
+}
+
+static void acad_class_init(ObjectClass *class, const void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(class);
+    AcpiDevAmlIfClass *adevc = ACPI_DEV_AML_IF_CLASS(class);
+
+    dc->realize = acad_realize;
+    device_class_set_props(dc, acad_device_properties);
+    dc->vmsd = &acad_vmstate;
+    adevc->build_dev_aml = build_acad_aml;
+}
+
+static uint64_t acad_ioport_read(void *opaque, hwaddr addr, unsigned size)
+{
+    ACADState *s = opaque;
+
+    acad_get_dynamic_status(s);
+
+    switch (addr) {
+    case AC_STA_ADDR:
+        return s->state;
+    default:
+        warn_report("AC adapter: guest read unknown value.");
+        trace_acad_ioport_read_unknown();
+        return 0;
+    }
+}
+
+static const MemoryRegionOps acad_ops = {
+    .read = acad_ioport_read,
+    .impl = {
+        .min_access_size = 1,
+        .max_access_size = 1,
+    },
+};
+
+static void acad_instance_init(Object *obj)
+{
+    ACADState *s = AC_ADAPTER_DEVICE(obj);
+
+    memory_region_init_io(&s->io, obj, &acad_ops, s, "acad",
+                          AC_ADAPTER_LEN);
+}
+
+static const TypeInfo acad_info = {
+    .name          = TYPE_AC_ADAPTER,
+    .parent        = TYPE_ISA_DEVICE,
+    .instance_size = sizeof(ACADState),
+    .class_init    = acad_class_init,
+    .instance_init = acad_instance_init,
+    .interfaces = (InterfaceInfo[]) {
+        { TYPE_ACPI_DEV_AML_IF },
+        { },
+    },
+};
+
+static ACADState *find_acad_device(void)
+{
+    Object *o = object_resolve_path_type("", TYPE_AC_ADAPTER, NULL);
+    if (!o) {
+        return NULL;
+    }
+    return AC_ADAPTER_DEVICE(o);
+}
+
+void qmp_ac_adapter_set_state(bool connected, Error **errp)
+{
+    ACADState *s = find_acad_device();
+
+    if (!s) {
+        error_setg(errp, "No AC adapter device found");
+        return;
+    }
+
+    s->qmp_connected = connected;
+
+    Object *obj = object_resolve_path_type("", TYPE_ACPI_DEVICE_IF, NULL);
+    if (obj) {
+        acpi_send_event(DEVICE(obj), ACPI_AC_ADAPTER_CHANGE_STATUS);
+    }
+}
+
+AcAdapterInfo *qmp_query_ac_adapter(Error **errp)
+{
+    ACADState *s = find_acad_device();
+    AcAdapterInfo *ret;
+
+    if (!s) {
+        error_setg(errp, "No AC adapter device found");
+        return NULL;
+    }
+
+    ret = g_new0(AcAdapterInfo, 1);
+
+    if (s->use_qmp_control) {
+        ret->connected = s->qmp_connected;
+    } else {
+        acad_get_dynamic_status(s);
+        ret->connected = (s->state == AC_ADAPTER_ONLINE);
+    }
+
+    return ret;
+}
+
+static void acad_register_types(void)
+{
+    type_register_static(&acad_info);
+}
+
+type_init(acad_register_types)
diff --git a/hw/acpi/meson.build b/hw/acpi/meson.build
index 10379a7b2c..2b24951f28 100644
--- a/hw/acpi/meson.build
+++ b/hw/acpi/meson.build
@@ -32,6 +32,7 @@ if have_tpm
   acpi_ss.add(files('tpm.c'))
 endif
 acpi_ss.add(when: 'CONFIG_BATTERY', if_true: files('battery.c'))
+acpi_ss.add(when: 'CONFIG_AC_ADAPTER', if_true: files('acad.c'))
 system_ss.add(when: 'CONFIG_ACPI', if_false: files('acpi-stub.c', 'aml-build-stub.c', 'ghes-stub.c', 'acpi_interface.c'))
 system_ss.add(when: 'CONFIG_ACPI_PCI_BRIDGE', if_false: files('pci-bridge-stub.c'))
 system_ss.add_all(when: 'CONFIG_ACPI', if_true: acpi_ss)
diff --git a/hw/acpi/trace-events b/hw/acpi/trace-events
index dd3e815482..68ac6e9701 100644
--- a/hw/acpi/trace-events
+++ b/hw/acpi/trace-events
@@ -92,3 +92,8 @@ acpi_nvdimm_invalid_revision(uint32_t revision) "Revision 0x%" PRIx32 " is not s
 battery_realize(void) "Battery device realize entry"
 battery_get_dynamic_status(uint32_t state, uint32_t rate, uint32_t charge) "Battery read state: 0x%"PRIx32", rate: %"PRIu32", charge: %"PRIu32
 battery_ioport_read_unknown(void) "Battery read unknown"
+
+# acad.c
+acad_realize(void) "AC adapter device realize entry"
+acad_get_dynamic_status(uint8_t state) "AC adapter read state: %"PRIu8
+acad_ioport_read_unknown(void) "AC adapter read unknown"
diff --git a/hw/i386/Kconfig b/hw/i386/Kconfig
index 2c878fd112..baab382a2e 100644
--- a/hw/i386/Kconfig
+++ b/hw/i386/Kconfig
@@ -40,6 +40,7 @@ config PC
     imply NVDIMM
     imply FDC_ISA
     imply BATTERY
+    imply AC_ADAPTER
     select I8259
     select I8254
     select PCKBD
diff --git a/include/hw/acpi/acad.h b/include/hw/acpi/acad.h
new file mode 100644
index 0000000000..a4e7149488
--- /dev/null
+++ b/include/hw/acpi/acad.h
@@ -0,0 +1,27 @@
+/*
+ * QEMU emulated AC adapter device.
+ *
+ * Copyright (c) 2019 Janus Technologies, Inc. (http://janustech.com)
+ *
+ * Authors:
+ *     Leonid Bloch <lb.workbox@gmail.com>
+ *     Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
+ *     Dmitry Fleytman <dmitry.fleytman@gmail.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ */
+
+#ifndef HW_ACPI_AC_ADAPTER_H
+#define HW_ACPI_AC_ADAPTER_H
+
+#define TYPE_AC_ADAPTER                  "acad"
+#define AC_ADAPTER_IOPORT_PROP           "ioport"
+#define AC_ADAPTER_PATH_PROP             "sysfs_path"
+#define AC_ADAPTER_PROBE_STATE_INTERVAL  "probe_interval"
+
+#define AC_ADAPTER_VAL_UNKNOWN  0xFFFFFFFF
+
+#define AC_ADAPTER_LEN          1
+
+#endif
diff --git a/include/hw/acpi/acpi_dev_interface.h b/include/hw/acpi/acpi_dev_interface.h
index 3064ef6734..588fbbd05f 100644
--- a/include/hw/acpi/acpi_dev_interface.h
+++ b/include/hw/acpi/acpi_dev_interface.h
@@ -14,6 +14,7 @@ typedef enum {
     ACPI_VMGENID_CHANGE_STATUS = 32,
     ACPI_POWER_DOWN_STATUS = 64,
     ACPI_BATTERY_CHANGE_STATUS = 128,
+    ACPI_AC_ADAPTER_CHANGE_STATUS = 1024,
 } AcpiEventStatusBits;
 
 #define TYPE_ACPI_DEVICE_IF "acpi-device-interface"
diff --git a/qapi/acpi.json b/qapi/acpi.json
index d1ad663bfd..52e151f0e6 100644
--- a/qapi/acpi.json
+++ b/qapi/acpi.json
@@ -215,3 +215,52 @@
 ##
 { 'command': 'query-battery',
   'returns': 'BatteryInfo' }
+
+##
+# @ac-adapter-set-state:
+#
+# Set the state of the emulated AC adapter device
+#
+# @connected: whether the AC adapter is connected
+#
+
+#
+# Since: 10.2
+#
+# .. qmp-example::
+#
+#     -> { "execute": "ac-adapter-set-state",
+#          "arguments": { "connected": true } }
+#     <- { "return": {} }
+##
+{ 'command': 'ac-adapter-set-state',
+  'data': { 'connected': 'bool' } }
+
+##
+# @AcAdapterInfo:
+#
+# AC adapter state information
+#
+# @connected: whether the AC adapter is connected
+#
+# Since: 10.2
+##
+{ 'struct': 'AcAdapterInfo',
+  'data': { 'connected': 'bool' } }
+
+##
+# @query-ac-adapter:
+#
+# Query the current state of the emulated AC adapter device
+#
+# Returns: AC adapter connection state
+#
+# Since: 10.2
+#
+# .. qmp-example::
+#
+#     -> { "execute": "query-ac-adapter" }
+#     <- { "return": { "connected": true } }
+##
+{ 'command': 'query-ac-adapter',
+  'returns': 'AcAdapterInfo' }
-- 
2.50.1