#include <linux/virtio.h>
#include <linux/spinlock.h>
#include <linux/virtio_config.h>
#include <linux/module.h>
#include <linux/idr.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 = container_of(_d,struct virtio_device,dev);
        return sprintf(buf, "0x%04x\n", dev->id.device);
}
static ssize_t vendor_show(struct device *_d,
                           struct device_attribute *attr, char *buf)
{
        struct virtio_device *dev = container_of(_d,struct virtio_device,dev);
        return sprintf(buf, "0x%04x\n", dev->id.vendor);
}
static ssize_t status_show(struct device *_d,
                           struct device_attribute *attr, char *buf)
{
        struct virtio_device *dev = container_of(_d,struct virtio_device,dev);
        return sprintf(buf, "0x%08x\n", dev->config->get_status(dev));
}
static ssize_t modalias_show(struct device *_d,
                             struct device_attribute *attr, char *buf)
{
        struct virtio_device *dev = container_of(_d,struct virtio_device,dev);

        return sprintf(buf, "virtio:d%08Xv%08X\n",
                       dev->id.device, dev->id.vendor);
}
static ssize_t features_show(struct device *_d,
                             struct device_attribute *attr, char *buf)
{
        struct virtio_device *dev = container_of(_d, struct virtio_device, dev);
        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 < ARRAY_SIZE(dev->features)*BITS_PER_LONG; i++)
                len += sprintf(buf+len, "%c",
                               test_bit(i, dev->features) ? '1' : '0');
        len += sprintf(buf+len, "\n");
        return len;
}
static struct device_attribute virtio_dev_attrs[] = {
        __ATTR_RO(device),
        __ATTR_RO(vendor),
        __ATTR_RO(status),
        __ATTR_RO(modalias),
        __ATTR_RO(features),
        __ATTR_NULL
};

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 = container_of(_dv,struct virtio_device,dev);
        const struct virtio_device_id *ids;

        ids = container_of(_dr, struct virtio_driver, driver)->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 = container_of(_dv,struct virtio_device,dev);

        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 = container_of(vdev->dev.driver,
                                                 struct virtio_driver, driver);

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

static int virtio_dev_probe(struct device *_d)
{
        int err, i;
        struct virtio_device *dev = container_of(_d,struct virtio_device,dev);
        struct virtio_driver *drv = container_of(dev->dev.driver,
                                                 struct virtio_driver, driver);
        u32 device_features;

        /* 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);

        /* Features supported by both device and driver into dev->features. */
        memset(dev->features, 0, sizeof(dev->features));
        for (i = 0; i < drv->feature_table_size; i++) {
                unsigned int f = drv->feature_table[i];
                BUG_ON(f >= 32);
                if (device_features & (1 << f))
                        set_bit(f, dev->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 & (1 << i))
                        set_bit(i, dev->features);

        dev->config->finalize_features(dev);

        err = drv->probe(dev);
        if (err)
                add_status(dev, VIRTIO_CONFIG_S_FAILED);
        else
                add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);

        return err;
}

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

        drv->remove(dev);

        /* Driver should have reset device. */
        BUG_ON(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_attrs = virtio_dev_attrs,
        .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);

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

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);
}
core_initcall(virtio_init);
module_exit(virtio_exit);

MODULE_LICENSE("GPL");