[PATCH v4 6/8] media: virtio: Add virtio_media_driver

[Brian Daniels <briandaniels@google.com>]

From: Alexandre Courbot <gnurou@gmail.com>

virtio_media_driver.c provides the expected driver hooks, and support
for mmapping and polling.

Signed-off-by: Alexandre Courbot <gnurou@gmail.com>
Co-developed-by: Brian Daniels <briandaniels@google.com>
Signed-off-by: Brian Daniels <briandaniels@google.com>
---
 drivers/media/virtio/virtio_media_driver.c | 959 +++++++++++++++++++++
 1 file changed, 959 insertions(+)
 create mode 100644 drivers/media/virtio/virtio_media_driver.c

diff --git a/drivers/media/virtio/virtio_media_driver.c b/drivers/media/virtio/virtio_media_driver.c
new file mode 100644
index 000000000..d6363c673
--- /dev/null
+++ b/drivers/media/virtio/virtio_media_driver.c
@@ -0,0 +1,959 @@
+// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0+
+
+/*
+ * Virtio-media driver.
+ *
+ * Copyright (c) 2024-2025 Google LLC.
+ */
+
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/dev_printk.h>
+#include <linux/mm.h>
+#include <linux/mutex.h>
+#include <linux/scatterlist.h>
+#include <linux/types.h>
+#include <linux/videodev2.h>
+#include <linux/vmalloc.h>
+#include <linux/wait.h>
+#include <linux/workqueue.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/virtio.h>
+#include <linux/virtio_config.h>
+#include <linux/virtio_ids.h>
+
+#include <media/frame_vector.h>
+#include <media/v4l2-dev.h>
+#include <media/v4l2-event.h>
+#include <media/videobuf2-memops.h>
+#include <media/v4l2-device.h>
+#include <media/v4l2-ioctl.h>
+
+#include "protocol.h"
+#include "session.h"
+#include "virtio_media.h"
+
+#define VIRTIO_MEDIA_NUM_EVENT_BUFS 16
+
+/* ID of the SHM region into which MMAP buffer will be mapped. */
+#define VIRTIO_MEDIA_SHM_MMAP 0
+
+/*
+ * Name of the driver to expose to user-space.
+ *
+ * This is configurable because v4l2-compliance has workarounds specific to
+ * some drivers. When proxying these directly from the host, this allows it to
+ * apply them as needed.
+ */
+char *virtio_media_driver_name;
+module_param_named(driver_name, virtio_media_driver_name, charp, 0660);
+
+/*
+ * Whether USERPTR buffers are allowed.
+ *
+ * This is disabled by default as USERPTR buffers are dangerous, but the option
+ * is left to enable them if desired.
+ */
+bool virtio_media_allow_userptr;
+module_param_named(allow_userptr, virtio_media_allow_userptr, bool, 0660);
+
+/**
+ * virtio_media_session_alloc - Allocate a new session.
+ * @vv: virtio-media device the session belongs to.
+ * @id: ID of the session.
+ * @nonblocking_dequeue: whether dequeuing of buffers should be blocking or
+ * not.
+ *
+ * The ``id`` and ``list`` fields must still be set by the caller.
+ */
+static struct virtio_media_session *
+virtio_media_session_alloc(struct virtio_media *vv, u32 id,
+			   struct file *file)
+{
+	struct virtio_media_session *session;
+	int i;
+	int ret;
+
+	session = kzalloc_obj(*session, GFP_KERNEL);
+	if (!session)
+		goto err_session;
+
+	session->shadow_buf = kzalloc(VIRTIO_SHADOW_BUF_SIZE, GFP_KERNEL);
+	if (!session->shadow_buf)
+		goto err_shadow_buf;
+
+	ret = sg_alloc_table(&session->command_sgs, DESC_CHAIN_MAX_LEN,
+			     GFP_KERNEL);
+	if (ret)
+		goto err_payload_sgs;
+
+	session->id = id;
+	session->nonblocking_dequeue = file->f_flags & O_NONBLOCK;
+
+	INIT_LIST_HEAD(&session->list);
+	v4l2_fh_init(&session->fh, &vv->video_dev);
+	virtio_media_session_fh_add(session, file);
+
+	for (i = 0; i <= VIRTIO_MEDIA_LAST_QUEUE; i++)
+		INIT_LIST_HEAD(&session->queues[i].pending_dqbufs);
+	mutex_init(&session->queues_lock);
+
+	init_waitqueue_head(&session->dqbuf_wait);
+
+	mutex_lock(&vv->sessions_lock);
+	list_add_tail(&session->list, &vv->sessions);
+	mutex_unlock(&vv->sessions_lock);
+
+	return session;
+
+err_payload_sgs:
+	kfree(session->shadow_buf);
+err_shadow_buf:
+	kfree(session);
+err_session:
+	return ERR_PTR(-ENOMEM);
+}
+
+/**
+ * virtio_media_session_free - Free all resources of a session.
+ * @vv: virtio-media device the session belongs to.
+ * @session: session to destroy.
+ *
+ * All the resources of @sesssion, as well as the backing memory of @session
+ * itself, are freed.
+ */
+static void virtio_media_session_free(struct virtio_media *vv,
+				      struct virtio_media_session *session)
+{
+	int i;
+
+	mutex_lock(&vv->sessions_lock);
+	list_del(&session->list);
+	mutex_unlock(&vv->sessions_lock);
+
+	virtio_media_session_fh_del(session);
+	v4l2_fh_exit(&session->fh);
+
+	sg_free_table(&session->command_sgs);
+
+	for (i = 0; i <= VIRTIO_MEDIA_LAST_QUEUE; i++)
+		vfree(session->queues[i].buffers);
+
+	kfree(session->shadow_buf);
+	kfree(session);
+}
+
+/**
+ * virtio_media_session_close - Close and free a session.
+ * @vv: virtio-media device the session belongs to.
+ * @session: session to close and destroy.
+ *
+ * This send the ``VIRTIO_MEDIA_CMD_CLOSE`` command to the device, and frees
+ * all resources used by @session.
+ */
+static int virtio_media_session_close(struct virtio_media *vv,
+				      struct virtio_media_session *session)
+{
+	struct virtio_media_cmd_close *cmd_close = &session->cmd.close;
+	struct scatterlist cmd_sg = {};
+	struct scatterlist *sgs[1] = { &cmd_sg };
+	int ret;
+
+	mutex_lock(&vv->vlock);
+
+	cmd_close->hdr.cmd = VIRTIO_MEDIA_CMD_CLOSE;
+	cmd_close->session_id = session->id;
+
+	sg_set_buf(&cmd_sg, cmd_close, sizeof(*cmd_close));
+	sg_mark_end(&cmd_sg);
+
+	ret = virtio_media_send_command(vv, sgs, 1, 0, 0, NULL);
+	mutex_unlock(&vv->vlock);
+	if (ret < 0)
+		return ret;
+
+	virtio_media_session_free(vv, session);
+
+	return 0;
+}
+
+/**
+ * virtio_media_find_session - Lookup for the session with a given ID.
+ * @vv: virtio-media device to lookup the session from.
+ * @id: ID of the session to lookup.
+ */
+static struct virtio_media_session *
+virtio_media_find_session(struct virtio_media *vv, u32 id)
+{
+	struct list_head *p;
+	struct virtio_media_session *session = NULL;
+
+	mutex_lock(&vv->sessions_lock);
+	list_for_each(p, &vv->sessions) {
+		struct virtio_media_session *s =
+			list_entry(p, struct virtio_media_session, list);
+		if (s->id == id) {
+			session = s;
+			break;
+		}
+	}
+	mutex_unlock(&vv->sessions_lock);
+
+	return session;
+}
+
+/**
+ * struct virtio_media_cmd_callback_param - Callback parameters to the virtio
+ *                                          command queue.
+ * @vv: virtio-media device in use.
+ * @done: flag to be switched once the command is completed.
+ * @resp_len: length of the received response from the command. Only valid
+ * after @done_flag has switched to ``true``.
+ */
+struct virtio_media_cmd_callback_param {
+	struct virtio_media *vv;
+	bool done;
+	size_t resp_len;
+};
+
+/**
+ * commandq_callback: Callback for the command queue.
+ * @queue: command virtqueue.
+ *
+ * This just wakes up the thread that was waiting on the command to complete.
+ */
+static void commandq_callback(struct virtqueue *queue)
+{
+	unsigned int len;
+	struct virtio_media_cmd_callback_param *param;
+
+process_bufs:
+	while ((param = virtqueue_get_buf(queue, &len))) {
+		param->done = true;
+		param->resp_len = len;
+		wake_up(&param->vv->wq);
+	}
+
+	if (!virtqueue_enable_cb(queue)) {
+		virtqueue_disable_cb(queue);
+		goto process_bufs;
+	}
+}
+
+/**
+ * virtio_media_kick_command - send a command to the commandq.
+ * @vv: virtio-media device in use.
+ * @sgs: descriptor chain to send.
+ * @out_sgs: number of device-readable descriptors in @sgs.
+ * @in_sgs: number of device-writable descriptors in @sgs.
+ * @resp_len: output parameter. Upon success, contains the size of the response
+ * in bytes.
+ *
+ */
+static int virtio_media_kick_command(struct virtio_media *vv,
+				     struct scatterlist **sgs,
+				     const size_t out_sgs, const size_t in_sgs,
+				     size_t *resp_len)
+{
+	struct virtio_media_cmd_callback_param cb_param = {
+		.vv = vv,
+		.done = false,
+		.resp_len = 0,
+	};
+	struct virtio_media_resp_header *resp_header;
+	int ret;
+
+	ret = virtqueue_add_sgs(vv->commandq, sgs, out_sgs, in_sgs, &cb_param,
+				GFP_ATOMIC);
+	if (ret) {
+		v4l2_err(&vv->v4l2_dev,
+			 "failed to add sgs to command virtqueue\n");
+		return ret;
+	}
+
+	if (!virtqueue_kick(vv->commandq)) {
+		v4l2_err(&vv->v4l2_dev, "failed to kick command virtqueue\n");
+		return -EINVAL;
+	}
+
+	/* Wait for the response. */
+	ret = wait_event_timeout(vv->wq, cb_param.done, 5 * HZ);
+	if (ret == 0) {
+		v4l2_err(&vv->v4l2_dev,
+			 "timed out waiting for response to command\n");
+		return -ETIMEDOUT;
+	}
+
+	if (resp_len)
+		*resp_len = cb_param.resp_len;
+
+	if (in_sgs > 0) {
+		/*
+		 * If we expect a response, make sure we have at least a
+		 * response header - anything shorter is invalid.
+		 */
+		if (cb_param.resp_len < sizeof(*resp_header)) {
+			v4l2_err(&vv->v4l2_dev,
+				 "received response header is too short\n");
+			return -EINVAL;
+		}
+
+		resp_header = sg_virt(sgs[out_sgs]);
+		if (resp_header->status)
+			/* Host returns a positive error code. */
+			return -resp_header->status;
+	}
+
+	return 0;
+}
+
+/**
+ * virtio_media_send_command - Send a command to the device and wait for its
+ * response.
+ * @vv: virtio-media device in use.
+ * @sgs: descriptor chain to send.
+ * @out_sgs: number of device-readable descriptors in @sgs.
+ * @in_sgs: number of device-writable descriptors in @sgs.
+ * @minimum_resp_len: minimum length of the response expected by the caller
+ * when the command is successful. Anything shorter than that will result in
+ * ``-EINVAL`` being returned.
+ * @resp_len: output parameter. Upon success, contains the size of the response
+ * in bytes.
+ */
+int virtio_media_send_command(struct virtio_media *vv, struct scatterlist **sgs,
+			      const size_t out_sgs, const size_t in_sgs,
+			      size_t minimum_resp_len, size_t *resp_len)
+{
+	size_t local_resp_len = resp_len ? *resp_len : 0;
+	int ret = virtio_media_kick_command(vv, sgs, out_sgs, in_sgs,
+					    &local_resp_len);
+	if (resp_len)
+		*resp_len = local_resp_len;
+
+	/*
+	 * If the host could not process the command, there is no valid
+	 * response.
+	 */
+	if (ret < 0)
+		return ret;
+
+	/* Make sure the host wrote a complete reply. */
+	if (local_resp_len < minimum_resp_len) {
+		v4l2_err(&vv->v4l2_dev,
+			 "received response is too short: received %zu, expected at least %zu\n",
+			 local_resp_len, minimum_resp_len);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/**
+ * virtio_media_send_event_buffer() - Sends an event buffer to the host so it
+ * can return it with an event.
+ * @vv: virtio-media device in use.
+ * @event_buffer: pointer to the event buffer to send to the device.
+ */
+static int virtio_media_send_event_buffer(struct virtio_media *vv,
+					  void *event_buffer)
+{
+	struct scatterlist *sgs[1], vresp;
+	int ret;
+
+	sg_init_one(&vresp, event_buffer, VIRTIO_MEDIA_EVENT_MAX_SIZE);
+	sgs[0] = &vresp;
+
+	ret = virtqueue_add_sgs(vv->eventq, sgs, 0, 1, event_buffer,
+				GFP_ATOMIC);
+	if (ret) {
+		v4l2_err(&vv->v4l2_dev,
+			 "failed to add sgs to event virtqueue\n");
+		return ret;
+	}
+
+	if (!virtqueue_kick(vv->eventq)) {
+		v4l2_err(&vv->v4l2_dev, "failed to kick event virtqueue\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/**
+ * eventq_callback() - Callback for the event queue.
+ * @queue: event virtqueue.
+ *
+ * This just schedules for event work to be run.
+ */
+static void eventq_callback(struct virtqueue *queue)
+{
+	struct virtio_media *vv = queue->vdev->priv;
+
+	schedule_work(&vv->eventq_work);
+}
+
+/**
+ * virtio_media_process_dqbuf_event() - Process a dequeued event for a session.
+ * @vv: virtio-media device in use.
+ * @session: session the event is addressed to.
+ * @dqbuf_evt: the dequeued event to process.
+ *
+ * Invalid events are ignored with an error log.
+ */
+static void
+virtio_media_process_dqbuf_event(struct virtio_media *vv,
+				 struct virtio_media_session *session,
+				 struct virtio_media_event_dqbuf *dqbuf_evt)
+{
+	struct virtio_media_buffer *dqbuf;
+	const enum v4l2_buf_type queue_type = dqbuf_evt->buffer.type;
+	struct virtio_media_queue_state *queue;
+	typeof(dqbuf->buffer.m) buffer_m;
+	typeof(dqbuf->buffer.m.planes[0].m) plane_m;
+	int i;
+
+	if (queue_type >= ARRAY_SIZE(session->queues)) {
+		v4l2_err(&vv->v4l2_dev,
+			 "unmanaged queue %d passed to dqbuf event",
+			 dqbuf_evt->buffer.type);
+		return;
+	}
+	queue = &session->queues[queue_type];
+
+	if (dqbuf_evt->buffer.index >= queue->allocated_bufs) {
+		v4l2_err(&vv->v4l2_dev,
+			 "invalid buffer ID %d for queue %d in dqbuf event",
+			 dqbuf_evt->buffer.index, dqbuf_evt->buffer.type);
+		return;
+	}
+
+	dqbuf = &queue->buffers[dqbuf_evt->buffer.index];
+
+	/*
+	 * Preserve the 'm' union that was passed to us during QBUF so userspace
+	 * gets back the information it submitted.
+	 */
+	buffer_m = dqbuf->buffer.m;
+	memcpy(&dqbuf->buffer, &dqbuf_evt->buffer, sizeof(dqbuf->buffer));
+	dqbuf->buffer.m = buffer_m;
+	if (V4L2_TYPE_IS_MULTIPLANAR(dqbuf->buffer.type)) {
+		if (dqbuf->buffer.length > VIDEO_MAX_PLANES) {
+			v4l2_err(&vv->v4l2_dev,
+				 "invalid number of planes received from host for a multiplanar buffer\n");
+			return;
+		}
+		for (i = 0; i < dqbuf->buffer.length; i++) {
+			plane_m = dqbuf->planes[i].m;
+			memcpy(&dqbuf->planes[i], &dqbuf_evt->planes[i],
+			       sizeof(struct v4l2_plane));
+			dqbuf->planes[i].m = plane_m;
+		}
+	}
+
+	/* Set the DONE flag as the buffer is waiting for being dequeued. */
+	dqbuf->buffer.flags |= V4L2_BUF_FLAG_DONE;
+
+	mutex_lock(&session->queues_lock);
+	list_add_tail(&dqbuf->list, &queue->pending_dqbufs);
+	queue->queued_bufs -= 1;
+	mutex_unlock(&session->queues_lock);
+
+	wake_up(&session->dqbuf_wait);
+}
+
+/**
+ * virtio_media_process_events() - Process all pending events on a device.
+ * @vv: device which pending events we want to process.
+ *
+ * Retrieves all pending events on @vv's event queue and dispatch them to their
+ * corresponding session.
+ *
+ * Invalid events are ignored with an error log.
+ */
+void virtio_media_process_events(struct virtio_media *vv)
+{
+	struct virtio_media_event_error *error_evt;
+	struct virtio_media_event_dqbuf *dqbuf_evt;
+	struct virtio_media_event_event *event_evt;
+	struct virtio_media_session *session;
+	struct virtio_media_event_header *evt;
+	unsigned int len;
+
+	mutex_lock(&vv->events_lock);
+
+process_bufs:
+	while ((evt = virtqueue_get_buf(vv->eventq, &len))) {
+		/* Make sure we received enough data */
+		if (len < sizeof(*evt)) {
+			v4l2_err(&vv->v4l2_dev,
+				 "event is too short: got %u, expected at least %zu\n",
+				 len, sizeof(*evt));
+			goto end_of_event;
+		}
+
+		session = virtio_media_find_session(vv, evt->session_id);
+		if (!session) {
+			v4l2_err(&vv->v4l2_dev, "cannot find session %d\n",
+				 evt->session_id);
+			goto end_of_event;
+		}
+
+		switch (evt->event) {
+		case VIRTIO_MEDIA_EVT_ERROR:
+			if (len < sizeof(*error_evt)) {
+				v4l2_err(&vv->v4l2_dev,
+					 "error event is too short: got %u, expected %zu\n",
+					 len, sizeof(*error_evt));
+				break;
+			}
+			error_evt = (struct virtio_media_event_error *)evt;
+			v4l2_err(&vv->v4l2_dev,
+				 "received error %d for session %d",
+				 error_evt->errno, error_evt->hdr.session_id);
+			virtio_media_session_close(vv, session);
+			break;
+
+		/*
+		 * Dequeued buffer: put it into the right queue so user-space
+		 * can dequeue it.
+		 */
+		case VIRTIO_MEDIA_EVT_DQBUF:
+			if (len < sizeof(*dqbuf_evt)) {
+				v4l2_err(&vv->v4l2_dev,
+					 "dqbuf event is too short: got %u, expected %zu\n",
+					 len, sizeof(*dqbuf_evt));
+				break;
+			}
+			dqbuf_evt = (struct virtio_media_event_dqbuf *)evt;
+			virtio_media_process_dqbuf_event(vv, session,
+							 dqbuf_evt);
+			break;
+
+		case VIRTIO_MEDIA_EVT_EVENT:
+			if (len < sizeof(*event_evt)) {
+				v4l2_err(&vv->v4l2_dev,
+					 "session event is too short: got %u expected %zu\n",
+					 len, sizeof(*event_evt));
+				break;
+			}
+
+			event_evt = (struct virtio_media_event_event *)evt;
+			v4l2_event_queue_fh(&session->fh, &event_evt->event);
+			break;
+
+		default:
+			v4l2_err(&vv->v4l2_dev, "unknown event type %d\n",
+				 evt->event);
+			break;
+		}
+
+end_of_event:
+		virtio_media_send_event_buffer(vv, evt);
+	}
+
+	if (!virtqueue_enable_cb(vv->eventq)) {
+		virtqueue_disable_cb(vv->eventq);
+		goto process_bufs;
+	}
+
+	mutex_unlock(&vv->events_lock);
+}
+
+static void virtio_media_event_work(struct work_struct *work)
+{
+	struct virtio_media *vv =
+		container_of(work, struct virtio_media, eventq_work);
+
+	virtio_media_process_events(vv);
+}
+
+/**
+ * virtio_media_device_open() - Create a new session from an opened file.
+ * @file: opened file for the session.
+ */
+static int virtio_media_device_open(struct file *file)
+{
+	struct video_device *video_dev = video_devdata(file);
+	struct virtio_media *vv = to_virtio_media(video_dev);
+	struct virtio_media_cmd_open *cmd_open = &vv->cmd.open;
+	struct virtio_media_resp_open *resp_open = &vv->resp.open;
+	struct scatterlist cmd_sg = {}, resp_sg = {};
+	struct scatterlist *sgs[2] = { &cmd_sg, &resp_sg };
+	struct virtio_media_session *session;
+	u32 session_id;
+	int ret;
+
+	mutex_lock(&vv->vlock);
+
+	sg_set_buf(&cmd_sg, cmd_open, sizeof(*cmd_open));
+	sg_mark_end(&cmd_sg);
+
+	sg_set_buf(&resp_sg, resp_open, sizeof(*resp_open));
+	sg_mark_end(&resp_sg);
+
+	cmd_open->hdr.cmd = VIRTIO_MEDIA_CMD_OPEN;
+	ret = virtio_media_send_command(vv, sgs, 1, 1, sizeof(*resp_open),
+					NULL);
+	session_id = resp_open->session_id;
+	mutex_unlock(&vv->vlock);
+	if (ret < 0)
+		return ret;
+
+	session = virtio_media_session_alloc(vv, session_id, file);
+	if (IS_ERR(session))
+		return PTR_ERR(session);
+
+	file->private_data = &session->fh;
+
+	return 0;
+}
+
+/**
+ * virtio_media_device_close() - Close a previously opened session.
+ * @file: file of the session to close.
+ *
+ * This sends to ``VIRTIO_MEDIA_CMD_CLOSE`` command to the device, and close
+ * the session on the driver side.
+ */
+static int virtio_media_device_close(struct file *file)
+{
+	struct video_device *video_dev = video_devdata(file);
+	struct virtio_media *vv = to_virtio_media(video_dev);
+	struct virtio_media_session *session =
+		fh_to_session(file->private_data);
+
+	return virtio_media_session_close(vv, session);
+}
+
+/**
+ * virtio_media_device_poll() - Poll logic for a virtio-media device.
+ * @file: file of the session to poll.
+ * @wait: poll table to wait on.
+ */
+static __poll_t virtio_media_device_poll(struct file *file, poll_table *wait)
+{
+	struct virtio_media_session *session =
+		fh_to_session(file->private_data);
+	enum v4l2_buf_type capture_type =
+		session->uses_mplane ? V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE :
+				       V4L2_BUF_TYPE_VIDEO_CAPTURE;
+	enum v4l2_buf_type output_type =
+		session->uses_mplane ? V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE :
+				       V4L2_BUF_TYPE_VIDEO_OUTPUT;
+	struct virtio_media_queue_state *capture_queue =
+		&session->queues[capture_type];
+	struct virtio_media_queue_state *output_queue =
+		&session->queues[output_type];
+	__poll_t req_events = poll_requested_events(wait);
+	__poll_t rc = 0;
+
+	poll_wait(file, &session->dqbuf_wait, wait);
+	poll_wait(file, &session->fh.wait, wait);
+
+	mutex_lock(&session->queues_lock);
+	if (req_events & (EPOLLIN | EPOLLRDNORM)) {
+		if (!capture_queue->streaming ||
+		    (capture_queue->queued_bufs == 0 &&
+		     list_empty(&capture_queue->pending_dqbufs)))
+			rc |= EPOLLERR;
+		else if (!list_empty(&capture_queue->pending_dqbufs))
+			rc |= EPOLLIN | EPOLLRDNORM;
+	}
+	if (req_events & (EPOLLOUT | EPOLLWRNORM)) {
+		if (!output_queue->streaming)
+			rc |= EPOLLERR;
+		else if (output_queue->queued_bufs <
+			 output_queue->allocated_bufs)
+			rc |= EPOLLOUT | EPOLLWRNORM;
+	}
+	mutex_unlock(&session->queues_lock);
+
+	if (v4l2_event_pending(&session->fh))
+		rc |= EPOLLPRI;
+
+	return rc;
+}
+
+static void virtio_media_vma_close_locked(struct vm_area_struct *vma)
+{
+	struct virtio_media *vv = vma->vm_private_data;
+	struct virtio_media_cmd_munmap *cmd_munmap = &vv->cmd.munmap;
+	struct virtio_media_resp_munmap *resp_munmap = &vv->resp.munmap;
+	struct scatterlist cmd_sg = {}, resp_sg = {};
+	struct scatterlist *sgs[2] = { &cmd_sg, &resp_sg };
+	int ret;
+
+	sg_set_buf(&cmd_sg, cmd_munmap, sizeof(*cmd_munmap));
+	sg_mark_end(&cmd_sg);
+
+	sg_set_buf(&resp_sg, resp_munmap, sizeof(*resp_munmap));
+	sg_mark_end(&resp_sg);
+
+	cmd_munmap->hdr.cmd = VIRTIO_MEDIA_CMD_MUNMAP;
+	cmd_munmap->driver_addr =
+		(vma->vm_pgoff << PAGE_SHIFT) - vv->mmap_region.addr;
+	ret = virtio_media_send_command(vv, sgs, 1, 1, sizeof(*resp_munmap),
+					NULL);
+	if (ret < 0) {
+		v4l2_err(&vv->v4l2_dev, "host failed to unmap buffer: %d\n",
+			 ret);
+	}
+}
+
+/**
+ * virtio_media_vma_close() - Close a MMAP buffer mapping.
+ * @vma: VMA of the mapping to close.
+ *
+ * Inform the host that a previously created MMAP mapping is no longer needed
+ * and can be removed.
+ */
+static void virtio_media_vma_close(struct vm_area_struct *vma)
+{
+	struct virtio_media *vv = vma->vm_private_data;
+
+	mutex_lock(&vv->vlock);
+	virtio_media_vma_close_locked(vma);
+	mutex_unlock(&vv->vlock);
+}
+
+static const struct vm_operations_struct virtio_media_vm_ops = {
+	.close = virtio_media_vma_close,
+};
+
+/**
+ * virtio_media_device_mmap - Perform a mmap request from userspace.
+ * @file: opened file of the session to map for.
+ * @vma: VM area struct describing the desired mapping.
+ *
+ * This requests the host to map a MMAP buffer for us, so we can then make that
+ * mapping visible into user-space address space.
+ */
+static int virtio_media_device_mmap(struct file *file,
+				    struct vm_area_struct *vma)
+{
+	struct video_device *video_dev = video_devdata(file);
+	struct virtio_media *vv = to_virtio_media(video_dev);
+	struct virtio_media_session *session =
+		fh_to_session(file->private_data);
+	struct virtio_media_cmd_mmap *cmd_mmap = &session->cmd.mmap;
+	struct virtio_media_resp_mmap *resp_mmap = &session->resp.mmap;
+	struct scatterlist cmd_sg = {}, resp_sg = {};
+	struct scatterlist *sgs[2] = { &cmd_sg, &resp_sg };
+	int ret;
+
+	if (!(vma->vm_flags & VM_SHARED))
+		return -EINVAL;
+	if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
+		return -EINVAL;
+
+	mutex_lock(&vv->vlock);
+
+	cmd_mmap->hdr.cmd = VIRTIO_MEDIA_CMD_MMAP;
+	cmd_mmap->session_id = session->id;
+	cmd_mmap->flags =
+		(vma->vm_flags & VM_WRITE) ? VIRTIO_MEDIA_MMAP_FLAG_RW : 0;
+	cmd_mmap->offset = vma->vm_pgoff << PAGE_SHIFT;
+
+	sg_set_buf(&cmd_sg, cmd_mmap, sizeof(*cmd_mmap));
+	sg_mark_end(&cmd_sg);
+
+	sg_set_buf(&resp_sg, resp_mmap, sizeof(*resp_mmap));
+	sg_mark_end(&resp_sg);
+
+	/*
+	 * The host performs reference counting and is smart enough to return
+	 * the same guest physical address if this is called several times on
+	 * the same
+	 * buffer.
+	 */
+	ret = virtio_media_send_command(vv, sgs, 1, 1, sizeof(*resp_mmap),
+					NULL);
+	if (ret < 0)
+		goto end;
+
+	vma->vm_private_data = vv;
+	/*
+	 * Keep the guest address at which the buffer is mapped since we will
+	 * use that to unmap.
+	 */
+	vma->vm_pgoff = (resp_mmap->driver_addr + vv->mmap_region.addr) >>
+			PAGE_SHIFT;
+
+	/*
+	 * We cannot let the mapping be larger than the buffer.
+	 */
+	if (vma->vm_end - vma->vm_start > PAGE_ALIGN(resp_mmap->len)) {
+		dev_dbg(&video_dev->dev,
+			"invalid MMAP, as it would overflow buffer length\n");
+		virtio_media_vma_close_locked(vma);
+		ret = -EINVAL;
+		goto end;
+	}
+
+	ret = io_remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
+				 vma->vm_end - vma->vm_start,
+				 vma->vm_page_prot);
+	if (ret)
+		goto end;
+
+	vma->vm_ops = &virtio_media_vm_ops;
+
+end:
+	mutex_unlock(&vv->vlock);
+	return ret;
+}
+
+static const struct v4l2_file_operations virtio_media_fops = {
+	.owner = THIS_MODULE,
+	.open = virtio_media_device_open,
+	.release = virtio_media_device_close,
+	.poll = virtio_media_device_poll,
+	.unlocked_ioctl = virtio_media_device_ioctl,
+	.mmap = virtio_media_device_mmap,
+};
+
+static int virtio_media_probe(struct virtio_device *virtio_dev)
+{
+	struct device *dev = &virtio_dev->dev;
+	struct virtqueue *vqs[2];
+	static struct virtqueue_info vq_info[2] = {
+		{
+			.name = "command",
+			.callback = commandq_callback,
+		},
+		{
+			.name = "event",
+			.callback = eventq_callback,
+		},
+	};
+	struct virtio_media *vv;
+	struct video_device *vd;
+	int i;
+	int ret;
+
+	vv = devm_kzalloc(dev, sizeof(*vv), GFP_KERNEL);
+	if (!vv)
+		return -ENOMEM;
+
+	vv->event_buffer = devm_kzalloc(dev,
+					VIRTIO_MEDIA_EVENT_MAX_SIZE *
+					VIRTIO_MEDIA_NUM_EVENT_BUFS,
+					GFP_KERNEL);
+	if (!vv->event_buffer)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&vv->sessions);
+	mutex_init(&vv->sessions_lock);
+	mutex_init(&vv->events_lock);
+	mutex_init(&vv->vlock);
+
+	vv->virtio_dev = virtio_dev;
+	virtio_dev->priv = vv;
+
+	init_waitqueue_head(&vv->wq);
+
+	ret = v4l2_device_register(dev, &vv->v4l2_dev);
+	if (ret)
+		return ret;
+
+	ret = virtio_find_vqs(virtio_dev, 2, vqs, vq_info, NULL);
+	if (ret)
+		goto err_find_vqs;
+
+	vv->commandq = vqs[0];
+	vv->eventq = vqs[1];
+	INIT_WORK(&vv->eventq_work, virtio_media_event_work);
+
+	/* Get MMAP buffer mapping SHM region */
+	virtio_get_shm_region(virtio_dev, &vv->mmap_region,
+			      VIRTIO_MEDIA_SHM_MMAP);
+
+	vd = &vv->video_dev;
+
+	vd->v4l2_dev = &vv->v4l2_dev;
+	vd->vfl_type = VFL_TYPE_VIDEO;
+	vd->ioctl_ops = &virtio_media_ioctl_ops;
+	vd->fops = &virtio_media_fops;
+	vd->device_caps = virtio_cread32(virtio_dev, 0);
+	if (vd->device_caps & (V4L2_CAP_VIDEO_M2M | V4L2_CAP_VIDEO_M2M_MPLANE))
+		vd->vfl_dir = VFL_DIR_M2M;
+	else if (vd->device_caps &
+		 (V4L2_CAP_VIDEO_OUTPUT | V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE))
+		vd->vfl_dir = VFL_DIR_TX;
+	else
+		vd->vfl_dir = VFL_DIR_RX;
+	vd->release = video_device_release_empty;
+	strscpy(vd->name, "virtio-media", sizeof(vd->name));
+
+	video_set_drvdata(vd, vv);
+
+	ret = video_register_device(vd, virtio_cread32(virtio_dev, 4), 0);
+	if (ret)
+		goto err_register_device;
+
+	for (i = 0; i < VIRTIO_MEDIA_NUM_EVENT_BUFS; i++) {
+		void *ebuf = vv->event_buffer + VIRTIO_MEDIA_EVENT_MAX_SIZE * i;
+
+		ret = virtio_media_send_event_buffer(vv, ebuf);
+		if (ret)
+			goto err_send_event_buffer;
+	}
+
+	virtio_device_ready(virtio_dev);
+
+	return 0;
+
+err_send_event_buffer:
+	video_unregister_device(&vv->video_dev);
+err_register_device:
+	virtio_dev->config->del_vqs(virtio_dev);
+err_find_vqs:
+	v4l2_device_unregister(&vv->v4l2_dev);
+
+	return ret;
+}
+
+static void virtio_media_remove(struct virtio_device *virtio_dev)
+{
+	struct virtio_media *vv = virtio_dev->priv;
+	struct list_head *p, *n;
+
+	cancel_work_sync(&vv->eventq_work);
+	virtio_reset_device(virtio_dev);
+
+	v4l2_device_unregister(&vv->v4l2_dev);
+	virtio_dev->config->del_vqs(virtio_dev);
+	video_unregister_device(&vv->video_dev);
+
+	list_for_each_safe(p, n, &vv->sessions) {
+		struct virtio_media_session *s =
+			list_entry(p, struct virtio_media_session, list);
+
+		virtio_media_session_free(vv, s);
+	}
+}
+
+static struct virtio_device_id id_table[] = {
+	{ VIRTIO_ID_MEDIA, VIRTIO_DEV_ANY_ID },
+	{ 0 },
+};
+
+static unsigned int features[] = {};
+
+static struct virtio_driver virtio_media_driver = {
+	.feature_table = features,
+	.feature_table_size = ARRAY_SIZE(features),
+	.driver.name = VIRTIO_MEDIA_DEFAULT_DRIVER_NAME,
+	.driver.owner = THIS_MODULE,
+	.id_table = id_table,
+	.probe = virtio_media_probe,
+	.remove = virtio_media_remove,
+};
+
+module_virtio_driver(virtio_media_driver);
+
+MODULE_DEVICE_TABLE(virtio, id_table);
+MODULE_DESCRIPTION("virtio media driver");
+MODULE_AUTHOR("Alexandre Courbot <gnurou@gmail.com>");
+MODULE_LICENSE("Dual BSD/GPL");
-- 
2.55.0.rc0.799.gd6f94ed593-goog