#include <linux/virtio.h>
#include <linux/spinlock.h>
#include <linux/virtio_config.h>
#include <linux/module.h>
#include <linux/idr.h>
#include <uapi/linux/virtio_ids.h>

/* Unique numbering for virtio devices. */
static DEFINE_IDA(virtio_index_ida);

static ssize_t device_show(struct device *_d,
                           struct device_attribute *attr, char *buf)
{
        struct virtio_device *dev = dev_to_virtio(_d);
        return sprintf(buf, "0x%04x\n", dev->id.device);
}
static DEVICE_ATTR_RO(device);

static ssize_t vendor_show(struct device *_d,
                           struct device_attribute *attr, char *buf)
{
        struct virtio_device *dev = dev_to_virtio(_d);
        return sprintf(buf, "0x%04x\n", dev->id.vendor);
}
static DEVICE_ATTR_RO(vendor);

static ssize_t status_show(struct device *_d,
                           struct device_attribute *attr, char *buf)
{
        struct virtio_device *dev = dev_to_virtio(_d);
        return sprintf(buf, "0x%08x\n", dev->config->get_status(dev));
}
static DEVICE_ATTR_RO(status);

static ssize_t modalias_show(struct device *_d,
                             struct device_attribute *attr, char *buf)
{
        struct virtio_device *dev = dev_to_virtio(_d);
        return sprintf(buf, "virtio:d%08Xv%08X\n",
                       dev->id.device, dev->id.vendor);
}
static DEVICE_ATTR_RO(modalias);

static ssize_t features_show(struct device *_d,
                             struct device_attribute *attr, char *buf)
{
        struct virtio_device *dev = dev_to_virtio(_d);
        unsigned int i;
        ssize_t len = 0;

        /* We actually represent this as a bitstring, as it could be
         * arbitrary length in future. */
        for (i = 0; i < sizeof(dev->features)*8; i++)
                len += sprintf(buf+len, "%c",
                               __virtio_test_bit(dev, i) ? '1' : '0');
        len += sprintf(buf+len, "\n");
        return len;
}
static DEVICE_ATTR_RO(features);

static struct attribute *virtio_dev_attrs[] = {
        &dev_attr_device.attr,
        &dev_attr_vendor.attr,
        &dev_attr_status.attr,
        &dev_attr_modalias.attr,
        &dev_attr_features.attr,
        NULL,
};
ATTRIBUTE_GROUPS(virtio_dev);

static inline int virtio_id_match(const struct virtio_device *dev,
                                  const struct virtio_device_id *id)
{
        if (id->device != dev->id.device && id->device != VIRTIO_DEV_ANY_ID)
                return 0;

        return id->vendor == VIRTIO_DEV_ANY_ID || id->vendor == dev->id.vendor;
}

/* This looks through all the IDs a driver claims to support.  If any of them
 * match, we return 1 and the kernel will call virtio_dev_probe(). */
static int virtio_dev_match(struct device *_dv, struct device_driver *_dr)
{
        unsigned int i;
        struct virtio_device *dev = dev_to_virtio(_dv);
        const struct virtio_device_id *ids;

        ids = drv_to_virtio(_dr)->id_table;
        for (i = 0; ids[i].device; i++)
                if (virtio_id_match(dev, &ids[i]))
                        return 1;
        return 0;
}

static int virtio_uevent(struct device *_dv, struct kobj_uevent_env *env)
{
        struct virtio_device *dev = dev_to_virtio(_dv);

        return add_uevent_var(env, "MODALIAS=virtio:d%08Xv%08X",
                              dev->id.device, dev->id.vendor);
}

static void add_status(struct virtio_device *dev, unsigned status)
{
        dev->config->set_status(dev, dev->config->get_status(dev) | status);
}

void virtio_check_driver_offered_feature(const struct virtio_device *vdev,
                                         unsigned int fbit)
{
        unsigned int i;
        struct virtio_driver *drv = drv_to_virtio(vdev->dev.driver);

        for (i = 0; i < drv->feature_table_size; i++)
                if (drv->feature_table[i] == fbit)
                        return;

        if (drv->feature_table_legacy) {
                for (i = 0; i < drv->feature_table_size_legacy; i++)
                        if (drv->feature_table_legacy[i] == fbit)
                                return;
        }

        BUG();
}
EXPORT_SYMBOL_GPL(virtio_check_driver_offered_feature);

static void __virtio_config_changed(struct virtio_device *dev)
{
        struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);

        if (!dev->config_enabled)
                dev->config_change_pending = true;
        else if (drv && drv->config_changed)
                drv->config_changed(dev);
}

void virtio_config_changed(struct virtio_device *dev)
{
        unsigned long flags;

        spin_lock_irqsave(&dev->config_lock, flags);
        __virtio_config_changed(dev);
        spin_unlock_irqrestore(&dev->config_lock, flags);
}
EXPORT_SYMBOL_GPL(virtio_config_changed);

static void virtio_config_disable(struct virtio_device *dev)
{
        spin_lock_irq(&dev->config_lock);
        dev->config_enabled = false;
        spin_unlock_irq(&dev->config_lock);
}

static void virtio_config_enable(struct virtio_device *dev)
{
        spin_lock_irq(&dev->config_lock);
        dev->config_enabled = true;
        if (dev->config_change_pending)
                __virtio_config_changed(dev);
        dev->config_change_pending = false;
        spin_unlock_irq(&dev->config_lock);
}

static int virtio_finalize_features(struct virtio_device *dev)
{
        int ret = dev->config->finalize_features(dev);
        unsigned status;

        if (ret)
                return ret;

        if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
                return 0;

        add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK);
        status = dev->config->get_status(dev);
        if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) {
                dev_err(&dev->dev, "virtio: device refuses features: %x\n",
                        status);
                return -ENODEV;
        }
        return 0;
}

static int virtio_dev_probe(struct device *_d)
{
        int err, i;
        struct virtio_device *dev = dev_to_virtio(_d);
        struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
        u64 device_features;
        u64 driver_features;
        u64 driver_features_legacy;

        /* We have a driver! */
        add_status(dev, VIRTIO_CONFIG_S_DRIVER);

        /* Figure out what features the device supports. */
        device_features = dev->config->get_features(dev);

        /* Figure out what features the driver supports. */
        driver_features = 0;
        for (i = 0; i < drv->feature_table_size; i++) {
                unsigned int f = drv->feature_table[i];
                BUG_ON(f >= 64);
                driver_features |= (1ULL << f);
        }

        /* Some drivers have a separate feature table for virtio v1.0 */
        if (drv->feature_table_legacy) {
                driver_features_legacy = 0;
                for (i = 0; i < drv->feature_table_size_legacy; i++) {
                        unsigned int f = drv->feature_table_legacy[i];
                        BUG_ON(f >= 64);
                        driver_features_legacy |= (1ULL << f);
                }
        } else {
                driver_features_legacy = driver_features;
        }

        if (device_features & (1ULL << VIRTIO_F_VERSION_1))
                dev->features = driver_features & device_features;
        else
                dev->features = driver_features_legacy & device_features;

        /* Transport features always preserved to pass to finalize_features. */
        for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++)
                if (device_features & (1ULL << i))
                        __virtio_set_bit(dev, i);

        err = virtio_finalize_features(dev);
        if (err)
                goto err;

        err = drv->probe(dev);
        if (err)
                goto err;

        /* If probe didn't do it, mark device DRIVER_OK ourselves. */
        if (!(dev->config->get_status(dev) & VIRTIO_CONFIG_S_DRIVER_OK))
                virtio_device_ready(dev);

        if (drv->scan)
                drv->scan(dev);

        virtio_config_enable(dev);

        return 0;
err:
        add_status(dev, VIRTIO_CONFIG_S_FAILED);
        return err;

}

static int virtio_dev_remove(struct device *_d)
{
        struct virtio_device *dev = dev_to_virtio(_d);
        struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);

        virtio_config_disable(dev);

        drv->remove(dev);

        /* Driver should have reset device. */
        WARN_ON_ONCE(dev->config->get_status(dev));

        /* Acknowledge the device's existence again. */
        add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
        return 0;
}

static struct bus_type virtio_bus = {
        .name  = "virtio",
        .match = virtio_dev_match,
        .dev_groups = virtio_dev_groups,
        .uevent = virtio_uevent,
        .probe = virtio_dev_probe,
        .remove = virtio_dev_remove,
};

int register_virtio_driver(struct virtio_driver *driver)
{
        /* Catch this early. */
        BUG_ON(driver->feature_table_size && !driver->feature_table);
        driver->driver.bus = &virtio_bus;
        return driver_register(&driver->driver);
}
EXPORT_SYMBOL_GPL(register_virtio_driver);

void unregister_virtio_driver(struct virtio_driver *driver)
{
        driver_unregister(&driver->driver);
}
EXPORT_SYMBOL_GPL(unregister_virtio_driver);

int register_virtio_device(struct virtio_device *dev)
{
        int err;

        dev->dev.bus = &virtio_bus;

        /* Assign a unique device index and hence name. */
        err = ida_simple_get(&virtio_index_ida, 0, 0, GFP_KERNEL);
        if (err < 0)
                goto out;

        dev->index = err;
        dev_set_name(&dev->dev, "virtio%u", dev->index);

        spin_lock_init(&dev->config_lock);
        dev->config_enabled = false;
        dev->config_change_pending = false;

        /* We always start by resetting the device, in case a previous
         * driver messed it up.  This also tests that code path a little. */
        dev->config->reset(dev);

        /* Acknowledge that we've seen the device. */
        add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);

        INIT_LIST_HEAD(&dev->vqs);

        /* device_register() causes the bus infrastructure to look for a
         * matching driver. */
        err = device_register(&dev->dev);
out:
        if (err)
                add_status(dev, VIRTIO_CONFIG_S_FAILED);
        return err;
}
EXPORT_SYMBOL_GPL(register_virtio_device);

void unregister_virtio_device(struct virtio_device *dev)
{
        int index = dev->index; /* save for after device release */

        device_unregister(&dev->dev);
        ida_simple_remove(&virtio_index_ida, index);
}
EXPORT_SYMBOL_GPL(unregister_virtio_device);

#ifdef CONFIG_PM_SLEEP
int virtio_device_freeze(struct virtio_device *dev)
{
        struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);

        virtio_config_disable(dev);

        dev->failed = dev->config->get_status(dev) & VIRTIO_CONFIG_S_FAILED;

        if (drv && drv->freeze)
                return drv->freeze(dev);

        return 0;
}
EXPORT_SYMBOL_GPL(virtio_device_freeze);

int virtio_device_restore(struct virtio_device *dev)
{
        struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
        int ret;

        /* We always start by resetting the device, in case a previous
         * driver messed it up. */
        dev->config->reset(dev);

        /* Acknowledge that we've seen the device. */
        add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);

        /* Maybe driver failed before freeze.
         * Restore the failed status, for debugging. */
        if (dev->failed)
                add_status(dev, VIRTIO_CONFIG_S_FAILED);

        if (!drv)
                return 0;

        /* We have a driver! */
        add_status(dev, VIRTIO_CONFIG_S_DRIVER);

        ret = virtio_finalize_features(dev);
        if (ret)
                goto err;

        if (drv->restore) {
                ret = drv->restore(dev);
                if (ret)
                        goto err;
        }

        /* Finally, tell the device we're all set */
        add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);

        virtio_config_enable(dev);

        return 0;

err:
        add_status(dev, VIRTIO_CONFIG_S_FAILED);
        return ret;
}
EXPORT_SYMBOL_GPL(virtio_device_restore);
#endif

static int virtio_init(void)
{
        if (bus_register(&virtio_bus) != 0)
                panic("virtio bus registration failed");
        return 0;
}

static void __exit virtio_exit(void)
{
        bus_unregister(&virtio_bus);
        ida_destroy(&virtio_index_ida);
}
core_initcall(virtio_init);
module_exit(virtio_exit);

MODULE_LICENSE("GPL");