root/include/linux/virtio.h

INCLUDED FROM

#ifndef _LINUX_VIRTIO_H
#define _LINUX_VIRTIO_H
/* Everything a virtio driver needs to work with any particular virtio
 * implementation. */
#include <linux/types.h>
#include <linux/scatterlist.h>
#include <linux/spinlock.h>
#include <linux/device.h>
#include <linux/mod_devicetable.h>

/**
 * virtqueue - a queue to register buffers for sending or receiving.
 * @callback: the function to call when buffers are consumed (can be NULL).
 * @vdev: the virtio device this queue was created for.
 * @vq_ops: the operations for this virtqueue (see below).
 * @priv: a pointer for the virtqueue implementation to use.
 */
struct virtqueue
{
        void (*callback)(struct virtqueue *vq);
        struct virtio_device *vdev;
        struct virtqueue_ops *vq_ops;
        void *priv;
};

/**
 * virtqueue_ops - operations for virtqueue abstraction layer
 * @add_buf: expose buffer to other end
 *      vq: the struct virtqueue we're talking about.
 *      sg: the description of the buffer(s).
 *      out_num: the number of sg readable by other side
 *      in_num: the number of sg which are writable (after readable ones)
 *      data: the token identifying the buffer.
 *      Returns 0 or an error.
 * @kick: update after add_buf
 *      vq: the struct virtqueue
 *      After one or more add_buf calls, invoke this to kick the other side.
 * @get_buf: get the next used buffer
 *      vq: the struct virtqueue we're talking about.
 *      len: the length written into the buffer
 *      Returns NULL or the "data" token handed to add_buf.
 * @disable_cb: disable callbacks
 *      vq: the struct virtqueue we're talking about.
 *      Note that this is not necessarily synchronous, hence unreliable and only
 *      useful as an optimization.
 * @enable_cb: restart callbacks after disable_cb.
 *      vq: the struct virtqueue we're talking about.
 *      This re-enables callbacks; it returns "false" if there are pending
 *      buffers in the queue, to detect a possible race between the driver
 *      checking for more work, and enabling callbacks.
 *
 * Locking rules are straightforward: the driver is responsible for
 * locking.  No two operations may be invoked simultaneously, with the exception
 * of @disable_cb.
 *
 * All operations can be called in any context.
 */
struct virtqueue_ops {
        int (*add_buf)(struct virtqueue *vq,
                       struct scatterlist sg[],
                       unsigned int out_num,
                       unsigned int in_num,
                       void *data);

        void (*kick)(struct virtqueue *vq);

        void *(*get_buf)(struct virtqueue *vq, unsigned int *len);

        void (*disable_cb)(struct virtqueue *vq);
        bool (*enable_cb)(struct virtqueue *vq);
};

/**
 * virtio_device - representation of a device using virtio
 * @index: unique position on the virtio bus
 * @dev: underlying device.
 * @id: the device type identification (used to match it with a driver).
 * @config: the configuration ops for this device.
 * @features: the features supported by both driver and device.
 * @priv: private pointer for the driver's use.
 */
struct virtio_device
{
        int index;
        struct device dev;
        struct virtio_device_id id;
        struct virtio_config_ops *config;
        /* Note that this is a Linux set_bit-style bitmap. */
        unsigned long features[1];
        void *priv;
};

int register_virtio_device(struct virtio_device *dev);
void unregister_virtio_device(struct virtio_device *dev);

/**
 * virtio_driver - operations for a virtio I/O driver
 * @driver: underlying device driver (populate name and owner).
 * @id_table: the ids serviced by this driver.
 * @feature_table: an array of feature numbers supported by this device.
 * @feature_table_size: number of entries in the feature table array.
 * @probe: the function to call when a device is found.  Returns a token for
 *    remove, or PTR_ERR().
 * @remove: the function when a device is removed.
 * @config_changed: optional function to call when the device configuration
 *    changes; may be called in interrupt context.
 */
struct virtio_driver {
        struct device_driver driver;
        const struct virtio_device_id *id_table;
        const unsigned int *feature_table;
        unsigned int feature_table_size;
        int (*probe)(struct virtio_device *dev);
        void (*remove)(struct virtio_device *dev);
        void (*config_changed)(struct virtio_device *dev);
};

int register_virtio_driver(struct virtio_driver *drv);
void unregister_virtio_driver(struct virtio_driver *drv);
#endif /* _LINUX_VIRTIO_H */