Virtio interface

This attempts to implement a "virtual I/O" layer which should allow
common drivers to be efficiently used across most virtual I/O
mechanisms.  It will no-doubt need further enhancement.

The virtio drivers add buffers to virtio queues; as the buffers are consumed
the driver "interrupt" callbacks are invoked.

There is also a generic implementation of config space which drivers can query
to get setup information from the host.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Dor Laor <dor.laor@qumranet.com>
Cc: Arnd Bergmann <arnd@arndb.de>

1 files changed, 110 insertions, 0 deletions

diff --git a/include/linux/virtio.h b/include/linux/virtio.h
new file mode 100644
index 000000000000..14e1379876d3
--- /dev/null
+++ b/include/linux/virtio.h
@@ -0,0 +1,110 @@
+#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).
+ *    If this returns false, callbacks are suppressed until vq_ops->restart
+ *    is called.
+ * @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
+{
+        bool (*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.
+ * @restart: restart callbacks after callback returned false.
+ *      vq: the struct virtqueue we're talking about.
+ *      This returns "false" (and doesn't re-enable) if there are pending
+ *      buffers in the queue, to avoid a race.
+ * @shutdown: "unadd" all buffers.
+ *      vq: the struct virtqueue we're talking about.
+ *      Remove everything from the queue.
+ *
+ * Locking rules are straightforward: the driver is responsible for
+ * locking.  No two operations may be invoked simultaneously.
+ *
+ * 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);
+
+        bool (*restart)(struct virtqueue *vq);
+
+        void (*shutdown)(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.
+ * @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;
+        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.
+ * @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.
+ */
+struct virtio_driver {
+        struct device_driver driver;
+        const struct virtio_device_id *id_table;
+        int (*probe)(struct virtio_device *dev);
+        void (*remove)(struct virtio_device *dev);
+};
+
+int register_virtio_driver(struct virtio_driver *drv);
+void unregister_virtio_driver(struct virtio_driver *drv);
+#endif /* _LINUX_VIRTIO_H */