virtio.c

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

    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. */
    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_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)
{
    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);

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");