[1/2] hw/virtio: add boilerplate for vhost-user-gpio device

diff --git a/hw/virtio/Kconfig b/hw/virtio/Kconfig
index c144d42f9bd0..b16a63609530 100644
--- a/hw/virtio/Kconfig
+++ b/hw/virtio/Kconfig
@@ -59,6 +59,11 @@  config VIRTIO_MEM
     depends on VIRTIO_MEM_SUPPORTED
     select MEM_DEVICE
 
+config VHOST_USER_GPIO
+    bool
+    default y
+    depends on VIRTIO && VHOST_USER
+
 config VHOST_USER_I2C
     bool
     default y
diff --git a/hw/virtio/meson.build b/hw/virtio/meson.build
index 521f7d64a86a..c7e67adff337 100644
--- a/hw/virtio/meson.build
+++ b/hw/virtio/meson.build
@@ -29,6 +29,7 @@  virtio_ss.add(when: 'CONFIG_VHOST_USER_I2C', if_true: files('vhost-user-i2c.c'))
 virtio_ss.add(when: ['CONFIG_VIRTIO_PCI', 'CONFIG_VHOST_USER_I2C'], if_true: files('vhost-user-i2c-pci.c'))
 virtio_ss.add(when: 'CONFIG_VHOST_USER_RNG', if_true: files('vhost-user-rng.c'))
 virtio_ss.add(when: ['CONFIG_VHOST_USER_RNG', 'CONFIG_VIRTIO_PCI'], if_true: files('vhost-user-rng-pci.c'))
+virtio_ss.add(when: 'CONFIG_VHOST_USER_GPIO', if_true: files('vhost-user-gpio.c'))
 
 virtio_pci_ss = ss.source_set()
 virtio_pci_ss.add(when: 'CONFIG_VHOST_VSOCK', if_true: files('vhost-vsock-pci.c'))
diff --git a/hw/virtio/vhost-user-gpio.c b/hw/virtio/vhost-user-gpio.c
new file mode 100644
index 000000000000..c5f67c0104a9
--- /dev/null
+++ b/hw/virtio/vhost-user-gpio.c
@@ -0,0 +1,343 @@ 
+/*
+ * Vhost-user GPIO virtio device
+ *
+ * Copyright (c) 2022 Viresh Kumar <viresh.kumar@linaro.org>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "hw/qdev-properties.h"
+#include "hw/virtio/virtio-bus.h"
+#include "hw/virtio/vhost-user-gpio.h"
+#include "qemu/error-report.h"
+#include "standard-headers/linux/virtio_ids.h"
+
+static const int feature_bits[] = {
+    VIRTIO_GPIO_F_IRQ
+};
+
+static void vu_gpio_get_config(VirtIODevice *vdev, uint8_t *config)
+{
+    VHostUserGPIO *gpio = VHOST_USER_GPIO(vdev);
+
+    memcpy(config, &gpio->config, sizeof(gpio->config));
+}
+
+static int vu_gpio_config_notifier(struct vhost_dev *dev)
+{
+    VHostUserGPIO *gpio = VHOST_USER_GPIO(dev->vdev);
+
+    memcpy(dev->vdev->config, &gpio->config, sizeof(gpio->config));
+    virtio_notify_config(dev->vdev);
+
+    return 0;
+}
+
+const VhostDevConfigOps gpio_ops = {
+    .vhost_dev_config_notifier = vu_gpio_config_notifier,
+};
+
+static int vu_gpio_start(VirtIODevice *vdev)
+{
+    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
+    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+    VHostUserGPIO *gpio = VHOST_USER_GPIO(vdev);
+    int ret, i;
+
+    if (!k->set_guest_notifiers) {
+        error_report("binding does not support guest notifiers");
+        return -ENOSYS;
+    }
+
+    ret = vhost_dev_enable_notifiers(&gpio->vhost_dev, vdev);
+    if (ret < 0) {
+        error_report("Error enabling host notifiers: %d", ret);
+        return ret;
+    }
+
+    ret = k->set_guest_notifiers(qbus->parent, gpio->vhost_dev.nvqs, true);
+    if (ret < 0) {
+        error_report("Error binding guest notifier: %d", ret);
+        goto err_host_notifiers;
+    }
+
+    gpio->vhost_dev.acked_features = vdev->guest_features;
+
+    ret = vhost_dev_start(&gpio->vhost_dev, vdev);
+    if (ret < 0) {
+        error_report("Error starting vhost-user-gpio: %d", ret);
+        goto err_guest_notifiers;
+    }
+
+    /*
+     * guest_notifier_mask/pending not used yet, so just unmask
+     * everything here. virtio-pci will do the right thing by
+     * enabling/disabling irqfd.
+     */
+    for (i = 0; i < gpio->vhost_dev.nvqs; i++) {
+        vhost_virtqueue_mask(&gpio->vhost_dev, vdev, i, false);
+    }
+
+    return 0;
+
+err_guest_notifiers:
+    k->set_guest_notifiers(qbus->parent, gpio->vhost_dev.nvqs, false);
+err_host_notifiers:
+    vhost_dev_disable_notifiers(&gpio->vhost_dev, vdev);
+
+    return ret;
+}
+
+static void vu_gpio_stop(VirtIODevice *vdev)
+{
+    VHostUserGPIO *gpio = VHOST_USER_GPIO(vdev);
+    BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
+    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+    int ret;
+
+    if (!k->set_guest_notifiers) {
+        return;
+    }
+
+    vhost_dev_stop(&gpio->vhost_dev, vdev);
+
+    ret = k->set_guest_notifiers(qbus->parent, gpio->vhost_dev.nvqs, false);
+    if (ret < 0) {
+        error_report("vhost guest notifier cleanup failed: %d", ret);
+        return;
+    }
+
+    vhost_dev_disable_notifiers(&gpio->vhost_dev, vdev);
+}
+
+static void vu_gpio_set_status(VirtIODevice *vdev, uint8_t status)
+{
+    VHostUserGPIO *gpio = VHOST_USER_GPIO(vdev);
+    bool should_start = status & VIRTIO_CONFIG_S_DRIVER_OK;
+
+    if (!vdev->vm_running) {
+        should_start = false;
+    }
+
+    if (!gpio->connected) {
+        return;
+    }
+
+    if (gpio->vhost_dev.started == should_start) {
+        return;
+    }
+
+    if (should_start) {
+        if (vu_gpio_start(vdev)) {
+            qemu_chr_fe_disconnect(&gpio->chardev);
+        }
+    } else {
+        vu_gpio_stop(vdev);
+    }
+}
+
+static uint64_t vu_gpio_get_features(VirtIODevice *vdev,
+                                    uint64_t requested_features, Error **errp)
+{
+    VHostUserGPIO *gpio = VHOST_USER_GPIO(vdev);
+
+    virtio_add_feature(&requested_features, VIRTIO_GPIO_F_IRQ);
+    return vhost_get_features(&gpio->vhost_dev, feature_bits, requested_features);
+}
+
+static void vu_gpio_handle_output(VirtIODevice *vdev, VirtQueue *vq)
+{
+    /*
+     * Not normally called; it's the daemon that handles the queue;
+     * however virtio's cleanup path can call this.
+     */
+}
+
+static void vu_gpio_guest_notifier_mask(VirtIODevice *vdev, int idx, bool mask)
+{
+    VHostUserGPIO *gpio = VHOST_USER_GPIO(vdev);
+
+    vhost_virtqueue_mask(&gpio->vhost_dev, vdev, idx, mask);
+}
+
+static void do_vhost_user_cleanup(VirtIODevice *vdev, VHostUserGPIO *gpio)
+{
+    virtio_delete_queue(gpio->command_vq);
+    virtio_delete_queue(gpio->interrupt_vq);
+    g_free(gpio->vhost_dev.vqs);
+    gpio->vhost_dev.vqs = NULL;
+    virtio_cleanup(vdev);
+    vhost_user_cleanup(&gpio->vhost_user);
+}
+
+static int vu_gpio_connect(DeviceState *dev)
+{
+    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+    VHostUserGPIO *gpio = VHOST_USER_GPIO(vdev);
+    Error *local_err = NULL;
+    int ret;
+
+    if (gpio->connected) {
+        return 0;
+    }
+    gpio->connected = true;
+
+    vhost_dev_set_config_notifier(&gpio->vhost_dev, &gpio_ops);
+
+    ret = vhost_dev_init(&gpio->vhost_dev, &gpio->vhost_user,
+                         VHOST_BACKEND_TYPE_USER, 0, &local_err);
+    if (ret < 0) {
+        error_report("vhost-user-gpio: vhost initialization failed: %s",
+                     strerror(-ret));
+        return ret;
+    }
+
+    /* restore vhost state */
+    if (virtio_device_started(vdev, vdev->status)) {
+        vu_gpio_start(vdev);
+    }
+
+    return 0;
+}
+
+static void vu_gpio_disconnect(DeviceState *dev)
+{
+    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+    VHostUserGPIO *gpio = VHOST_USER_GPIO(vdev);
+
+    if (!gpio->connected) {
+        return;
+    }
+    gpio->connected = false;
+
+    vu_gpio_stop(vdev);
+    vhost_dev_cleanup(&gpio->vhost_dev);
+}
+
+static void vu_gpio_event(void *opaque, QEMUChrEvent event)
+{
+    DeviceState *dev = opaque;
+    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+    VHostUserGPIO *gpio = VHOST_USER_GPIO(vdev);
+
+    switch (event) {
+    case CHR_EVENT_OPENED:
+        if (vu_gpio_connect(dev) < 0) {
+            qemu_chr_fe_disconnect(&gpio->chardev);
+            return;
+        }
+        break;
+    case CHR_EVENT_CLOSED:
+        vu_gpio_disconnect(dev);
+        break;
+    case CHR_EVENT_BREAK:
+    case CHR_EVENT_MUX_IN:
+    case CHR_EVENT_MUX_OUT:
+        /* Ignore */
+        break;
+    }
+}
+
+static void vu_gpio_device_realize(DeviceState *dev, Error **errp)
+{
+    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+    VHostUserGPIO *gpio = VHOST_USER_GPIO(dev);
+    Error *err = NULL;
+    int ret;
+
+    if (!gpio->chardev.chr) {
+        error_setg(errp, "vhost-user-gpio: chardev is mandatory");
+        return;
+    }
+
+    if (!vhost_user_init(&gpio->vhost_user, &gpio->chardev, errp)) {
+        return;
+    }
+
+    virtio_init(vdev, "vhost-user-gpio", VIRTIO_ID_GPIO, sizeof(gpio->config));
+
+    gpio->vhost_dev.nvqs = 2;
+    gpio->command_vq = virtio_add_queue(vdev, 256, vu_gpio_handle_output);
+    gpio->interrupt_vq = virtio_add_queue(vdev, 256, vu_gpio_handle_output);
+    gpio->vhost_dev.vqs = g_new0(struct vhost_virtqueue, gpio->vhost_dev.nvqs);
+
+    gpio->connected = false;
+
+    qemu_chr_fe_set_handlers(&gpio->chardev, NULL, NULL, vu_gpio_event, NULL,
+                             dev, NULL, true);
+
+reconnect:
+    if (qemu_chr_fe_wait_connected(&gpio->chardev, &err) < 0) {
+        error_report_err(err);
+        do_vhost_user_cleanup(vdev, gpio);
+        return;
+    }
+
+    /* check whether vhost_user_gpio_connect() failed or not */
+    if (!gpio->connected) {
+        goto reconnect;
+    }
+
+    ret = vhost_dev_get_config(&gpio->vhost_dev, (uint8_t *)&gpio->config,
+                               sizeof(gpio->config), errp);
+    if (ret < 0) {
+        error_report("vhost-user-gpio: get config failed");
+        goto reconnect;
+    }
+
+    return;
+}
+
+static void vu_gpio_device_unrealize(DeviceState *dev)
+{
+    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
+    VHostUserGPIO *gpio = VHOST_USER_GPIO(dev);
+
+    vu_gpio_set_status(vdev, 0);
+    qemu_chr_fe_set_handlers(&gpio->chardev, NULL, NULL, NULL, NULL, NULL, NULL,
+                             false);
+    vhost_dev_cleanup(&gpio->vhost_dev);
+    do_vhost_user_cleanup(vdev, gpio);
+}
+
+static const VMStateDescription vu_gpio_vmstate = {
+    .name = "vhost-user-gpio",
+    .unmigratable = 1,
+};
+
+static Property vu_gpio_properties[] = {
+    DEFINE_PROP_CHR("chardev", VHostUserGPIO, chardev),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static void vu_gpio_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
+
+    device_class_set_props(dc, vu_gpio_properties);
+    dc->vmsd = &vu_gpio_vmstate;
+    set_bit(DEVICE_CATEGORY_INPUT, dc->categories);
+    vdc->realize = vu_gpio_device_realize;
+    vdc->unrealize = vu_gpio_device_unrealize;
+    vdc->get_features = vu_gpio_get_features;
+    vdc->get_config = vu_gpio_get_config;
+    vdc->set_status = vu_gpio_set_status;
+    vdc->guest_notifier_mask = vu_gpio_guest_notifier_mask;
+}
+
+static const TypeInfo vu_gpio_info = {
+    .name = TYPE_VHOST_USER_GPIO,
+    .parent = TYPE_VIRTIO_DEVICE,
+    .instance_size = sizeof(VHostUserGPIO),
+    .class_init = vu_gpio_class_init,
+};
+
+static void vu_gpio_register_types(void)
+{
+    type_register_static(&vu_gpio_info);
+}
+
+type_init(vu_gpio_register_types)
diff --git a/include/hw/virtio/vhost-user-gpio.h b/include/hw/virtio/vhost-user-gpio.h
new file mode 100644
index 000000000000..afeb56f53e99
--- /dev/null
+++ b/include/hw/virtio/vhost-user-gpio.h
@@ -0,0 +1,35 @@ 
+/*
+ * Vhost-user GPIO virtio device
+ *
+ * Copyright (c) 2021 Viresh Kumar <viresh.kumar@linaro.org>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#ifndef _QEMU_VHOST_USER_GPIO_H
+#define _QEMU_VHOST_USER_GPIO_H
+
+#include "hw/virtio/virtio.h"
+#include "hw/virtio/vhost.h"
+#include "hw/virtio/vhost-user.h"
+#include "standard-headers/linux/virtio_gpio.h"
+#include "chardev/char-fe.h"
+
+#define TYPE_VHOST_USER_GPIO "vhost-user-gpio-device"
+OBJECT_DECLARE_SIMPLE_TYPE(VHostUserGPIO, VHOST_USER_GPIO);
+
+struct VHostUserGPIO {
+    /*< private >*/
+    VirtIODevice parent;
+    CharBackend chardev;
+    struct virtio_gpio_config config;
+    struct vhost_virtqueue *vhost_vq;
+    struct vhost_dev vhost_dev;
+    VhostUserState vhost_user;
+    VirtQueue *command_vq;
+    VirtQueue *interrupt_vq;
+    bool connected;
+    /*< public >*/
+};
+
+#endif /* _QEMU_VHOST_USER_GPIO_H */