virtio/virtio_ring: do some comment fixes

/**

 * virtqueue_add_sgs - expose buffers to other end

 * @vq: the struct virtqueue we're talking about.

 * @_vq: the struct virtqueue we're talking about.

 * @sgs: array of terminated scatterlists.

 * @out_num: the number of scatterlists readable by other side

 * @in_num: the number of scatterlists which are writable (after readable ones)

 * @out_sgs: the number of scatterlists readable by other side

 * @in_sgs: the number of scatterlists which are writable (after readable ones)

 * @data: the token identifying the buffer.

 * @gfp: how to do memory allocations (if necessary).

 *

/**

 * virtqueue_kick_prepare - first half of split virtqueue_kick call.

 * @vq: the struct virtqueue

 * @_vq: the struct virtqueue

 *

 * Instead of virtqueue_kick(), you can do:

 *	if (virtqueue_kick_prepare(vq))

/**

 * virtqueue_notify - second half of split virtqueue_kick call.

 * @vq: the struct virtqueue

 * @_vq: the struct virtqueue

 *

 * This does not need to be serialized.

 *

/**

 * virtqueue_get_buf - get the next used buffer

 * @vq: the struct virtqueue we're talking about.

 * @_vq: the struct virtqueue we're talking about.

 * @len: the length written into the buffer

 * @ctx: extra context for the token

 *

 * If the device wrote data into the buffer, @len will be set to the

 * amount written.  This means you don't need to clear the buffer

EXPORT_SYMBOL_GPL(virtqueue_get_buf);

/**

 * virtqueue_disable_cb - disable callbacks

 * @vq: the struct virtqueue we're talking about.

 * @_vq: the struct virtqueue we're talking about.

 *

 * Note that this is not necessarily synchronous, hence unreliable and only

 * useful as an optimization.

/**

 * virtqueue_enable_cb_prepare - restart callbacks after disable_cb

 * @vq: the struct virtqueue we're talking about.

 * @_vq: the struct virtqueue we're talking about.

 *

 * This re-enables callbacks; it returns current queue state

 * in an opaque unsigned value. This value should be later tested by

/**

 * virtqueue_poll - query pending used buffers

 * @vq: the struct virtqueue we're talking about.

 * @_vq: the struct virtqueue we're talking about.

 * @last_used_idx: virtqueue state (from call to virtqueue_enable_cb_prepare).

 *

 * Returns "true" if there are pending used buffers in the queue.

/**

 * virtqueue_enable_cb - restart callbacks after disable_cb.

 * @vq: the struct virtqueue we're talking about.

 * @_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

/**

 * virtqueue_enable_cb_delayed - restart callbacks after disable_cb.

 * @vq: the struct virtqueue we're talking about.

 * @_vq: the struct virtqueue we're talking about.

 *

 * This re-enables callbacks but hints to the other side to delay

 * interrupts until most of the available buffers have been processed;

/**

 * virtqueue_detach_unused_buf - detach first unused buffer

 * @vq: the struct virtqueue we're talking about.

 * @_vq: the struct virtqueue we're talking about.

 *

 * Returns NULL or the "data" token handed to virtqueue_add_*().

 * This is not valid on an active queue; it is useful only for device

/**

 * virtqueue_get_vring_size - return the size of the virtqueue's vring

 * @vq: the struct virtqueue containing the vring of interest.

 * @_vq: the struct virtqueue containing the vring of interest.

 *

 * Returns the size of the vring.  This is mainly used for boasting to

 * userspace.  Unlike other operations, this need not be serialized.