[PATCH v5 4/5] media: virtio: Add ioctl operations and driver logic

[Brian Daniels]

From: Alexandre Courbot <gnurou@xxxxxxxxx>

This patch adds the ioctl operations and the remaining driver logic
for polling and mmapping.

It adds drivers/media/virtio/virtio_media_ioctls.c and updates
virtio_media_driver.c to support poll, mmap, and ioctls.

Signed-off-by: Alexandre Courbot <gnurou@xxxxxxxxx>
Assisted-by: Antigravity:gemini-3.5-flash
Co-developed-by: Brian Daniels <briandaniels@xxxxxxxxxx>
Signed-off-by: Brian Daniels <briandaniels@xxxxxxxxxx>
---
 drivers/media/virtio/Makefile              |    2 +-
 drivers/media/virtio/virtio_media_driver.c |  195 +++
 drivers/media/virtio/virtio_media_ioctls.c | 1319 ++++++++++++++++++++
 3 files changed, 1515 insertions(+), 1 deletion(-)
 create mode 100644 drivers/media/virtio/virtio_media_ioctls.c

diff --git a/drivers/media/virtio/Makefile b/drivers/media/virtio/Makefile
index 8290d8506..f1bc8a3ce 100644
--- a/drivers/media/virtio/Makefile
+++ b/drivers/media/virtio/Makefile
@@ -2,6 +2,6 @@
 #
 # Makefile for the virtio-media device driver.
 
-virtio-media-objs := scatterlist_builder.o virtio_media_driver.o
+virtio-media-objs := scatterlist_builder.o virtio_media_ioctls.o virtio_media_driver.o
 
 obj-$(CONFIG_MEDIA_VIRTIO) += virtio-media.o
diff --git a/drivers/media/virtio/virtio_media_driver.c b/drivers/media/virtio/virtio_media_driver.c
index 938786b05..c431c3eb2 100644
--- a/drivers/media/virtio/virtio_media_driver.c
+++ b/drivers/media/virtio/virtio_media_driver.c
@@ -6,6 +6,7 @@
  * Copyright (c) 2024-2026 Google LLC.
  */
 
+#include <linux/bits.h>
 #include <linux/device.h>
 #include <linux/dev_printk.h>
 #include <linux/mutex.h>
@@ -19,6 +20,8 @@
 #include <linux/vmalloc.h>
 #include <linux/workqueue.h>
 #include <linux/dma-mapping.h>
+#include <linux/poll.h>
+#include <linux/mm.h>
 
 #include <media/v4l2-dev.h>
 #include <media/v4l2-device.h>
@@ -31,6 +34,12 @@
 
 #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
+
+/* Bit mask for the VIRTIO_MEDIA_MMAP_FLAG_RW flag */
+#define VIRTIO_MEDIA_MMAP_FLAG_RW_MASK BIT(VIRTIO_MEDIA_MMAP_FLAG_RW)
+
 /**
  * virtio_media_session_alloc() - Allocate a new session.
  * @vv: virtio-media device the session belongs to.
@@ -593,10 +602,191 @@ static int virtio_media_device_close(struct file *file)
 	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_MASK : 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)
@@ -654,9 +844,14 @@ static int virtio_media_probe(struct virtio_device *virtio_dev)
 	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->release = video_device_release_empty;
 	strscpy(vd->name, "virtio-media", sizeof(vd->name));
diff --git a/drivers/media/virtio/virtio_media_ioctls.c b/drivers/media/virtio/virtio_media_ioctls.c
new file mode 100644
index 000000000..f0b82b5ec
--- /dev/null
+++ b/drivers/media/virtio/virtio_media_ioctls.c
@@ -0,0 +1,1319 @@
+// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0+
+
+/*
+ * Ioctl implementations for the virtio-media driver.
+ *
+ * Copyright (c) 2024-2026 Google LLC.
+ */
+
+#include <linux/mutex.h>
+#include <linux/videodev2.h>
+#include <linux/virtio_config.h>
+#include <linux/vmalloc.h>
+#include <media/v4l2-event.h>
+#include <media/v4l2-ioctl.h>
+
+#include "scatterlist_builder.h"
+#include "virtio_media.h"
+
+/**
+ * virtio_media_send_r_ioctl() - Send a read-only ioctl to the device.
+ * @fh: file handler of the session doing the ioctl.
+ * @ioctl: ``VIDIOC_*`` ioctl code.
+ * @ioctl_data: pointer to the ioctl payload.
+ * @ioctl_data_len: length in bytes of the ioctl payload.
+ *
+ * Send an ioctl that has no driver payload, but expects a response from the
+ * host (i.e. an ioctl specified with ``_IOR``).
+ */
+static int virtio_media_send_r_ioctl(struct v4l2_fh *fh, u32 ioctl,
+				     void *ioctl_data, size_t ioctl_data_len)
+{
+	struct video_device *video_dev = fh->vdev;
+	struct virtio_media *vv = to_virtio_media(video_dev);
+	struct virtio_media_session *session = fh_to_session(fh);
+	struct scatterlist *sgs[3];
+	struct scatterlist_builder builder = {
+		.descs = session->command_sgs.sgl,
+		.num_descs = DESC_CHAIN_MAX_LEN,
+		.cur_desc = 0,
+		.shadow_buffer = session->shadow_buf,
+		.shadow_buffer_size = VIRTIO_SHADOW_BUF_SIZE,
+		.shadow_buffer_pos = 0,
+		.sgs = sgs,
+		.num_sgs = ARRAY_SIZE(sgs),
+		.cur_sg = 0,
+	};
+
+	/* Command descriptor */
+	int ret = scatterlist_builder_add_ioctl_cmd(&builder, session, ioctl);
+
+	if (ret)
+		return ret;
+
+	/* Response descriptor */
+	ret = scatterlist_builder_add_ioctl_resp(&builder, session);
+	if (ret)
+		return ret;
+
+	/* Response payload */
+	ret = scatterlist_builder_add_data(&builder, ioctl_data,
+					   ioctl_data_len);
+	if (ret) {
+		v4l2_err(&vv->v4l2_dev,
+			 "failed to prepare command descriptor chain\n");
+		return ret;
+	}
+
+	ret = virtio_media_send_command(vv, sgs, 1, 2,
+					sizeof(struct virtio_media_resp_ioctl) +
+					ioctl_data_len, NULL);
+	if (ret < 0)
+		return ret;
+
+	ret = scatterlist_builder_retrieve_data(&builder, 2, ioctl_data);
+	if (ret) {
+		v4l2_err(&vv->v4l2_dev,
+			 "failed to retrieve response descriptor chain\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+/**
+ * virtio_media_send_w_ioctl() - Send a write-only ioctl to the device.
+ * @fh: file handler of the session doing the ioctl.
+ * @ioctl: ``VIDIOC_*`` ioctl code.
+ * @ioctl_data: pointer to the ioctl payload.
+ * @ioctl_data_len: length in bytes of the ioctl payload.
+ *
+ * Send an ioctl that does not expect a reply beyond an error status (i.e. an
+ * ioctl specified with ``_IOW``) to the host.
+ */
+static int virtio_media_send_w_ioctl(struct v4l2_fh *fh, u32 ioctl,
+				     const void *ioctl_data,
+				     size_t ioctl_data_len)
+{
+	struct video_device *video_dev = fh->vdev;
+	struct virtio_media *vv = to_virtio_media(video_dev);
+	struct virtio_media_session *session = fh_to_session(fh);
+	struct scatterlist *sgs[3];
+	struct scatterlist_builder builder = {
+		.descs = session->command_sgs.sgl,
+		.num_descs = DESC_CHAIN_MAX_LEN,
+		.cur_desc = 0,
+		.shadow_buffer = session->shadow_buf,
+		.shadow_buffer_size = VIRTIO_SHADOW_BUF_SIZE,
+		.shadow_buffer_pos = 0,
+		.sgs = sgs,
+		.num_sgs = ARRAY_SIZE(sgs),
+		.cur_sg = 0,
+	};
+
+	/* Command descriptor */
+	int ret = scatterlist_builder_add_ioctl_cmd(&builder, session, ioctl);
+
+	if (ret)
+		return ret;
+
+	/* Command payload */
+	ret = scatterlist_builder_add_data(&builder, (void *)ioctl_data,
+					   ioctl_data_len);
+	if (ret) {
+		v4l2_err(&vv->v4l2_dev,
+			 "failed to prepare command descriptor chain\n");
+		return ret;
+	}
+
+	/* Response descriptor */
+	ret = scatterlist_builder_add_ioctl_resp(&builder, session);
+	if (ret)
+		return ret;
+
+	ret = virtio_media_send_command(vv, sgs, 2, 1,
+					sizeof(struct virtio_media_resp_ioctl),
+					NULL);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+/**
+ * virtio_media_send_wr_ioctl() - Send a read-write ioctl to the device.
+ * @fh: file handler of the session doing the ioctl.
+ * @ioctl: ``VIDIOC_*`` ioctl code.
+ * @ioctl_data: pointer to the ioctl payload.
+ * @ioctl_data_len: length in bytes of the ioctl payload.
+ * @minimum_resp_payload: minimum expected length of the response's payload.
+ *
+ * Sends an ioctl that expects a response of exactly the same size as the
+ * input (i.e. an ioctl specified with ``_IOWR``) to the host.
+ *
+ * This corresponds to what most V4L2 ioctls do. For instance
+ * ``VIDIOC_ENUM_FMT`` takes a partially-initialized &struct v4l2_fmtdesc
+ * and returns its filled version.
+ */
+static int virtio_media_send_wr_ioctl(struct v4l2_fh *fh, u32 ioctl,
+				      void *ioctl_data, size_t ioctl_data_len,
+				      size_t minimum_resp_payload)
+{
+	struct video_device *video_dev = fh->vdev;
+	struct virtio_media *vv = to_virtio_media(video_dev);
+	struct virtio_media_session *session = fh_to_session(fh);
+	struct scatterlist *sgs[4];
+	struct scatterlist_builder builder = {
+		.descs = session->command_sgs.sgl,
+		.num_descs = DESC_CHAIN_MAX_LEN,
+		.cur_desc = 0,
+		.shadow_buffer = session->shadow_buf,
+		.shadow_buffer_size = VIRTIO_SHADOW_BUF_SIZE,
+		.shadow_buffer_pos = 0,
+		.sgs = sgs,
+		.num_sgs = ARRAY_SIZE(sgs),
+		.cur_sg = 0,
+	};
+
+	/* Command descriptor */
+	int ret = scatterlist_builder_add_ioctl_cmd(&builder, session, ioctl);
+
+	if (ret)
+		return ret;
+
+	/* Command payload */
+	ret = scatterlist_builder_add_data(&builder, ioctl_data,
+					   ioctl_data_len);
+	if (ret) {
+		v4l2_err(&vv->v4l2_dev,
+			 "failed to prepare command descriptor chain\n");
+		return ret;
+	}
+
+	/* Response descriptor */
+	ret = scatterlist_builder_add_ioctl_resp(&builder, session);
+	if (ret)
+		return ret;
+
+	/* Response payload, same as command */
+	ret = scatterlist_builder_add_descriptor(&builder, 1);
+	if (ret)
+		return ret;
+
+	ret = virtio_media_send_command(vv, sgs, 2, 2,
+					sizeof(struct virtio_media_resp_ioctl) +
+						minimum_resp_payload,
+					NULL);
+	if (ret < 0)
+		return ret;
+
+	ret = scatterlist_builder_retrieve_data(&builder, 3, ioctl_data);
+	if (ret) {
+		v4l2_err(&vv->v4l2_dev,
+			 "failed to retrieve response descriptor chain\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+/**
+ * virtio_media_send_buffer_ioctl() - Send an ioctl taking a buffer as
+ * parameter to the device.
+ * @fh: file handler of the session doing the ioctl.
+ * @ioctl: ``VIDIOC_*`` ioctl code.
+ * @b: &struct v4l2_buffer to be sent as the ioctl payload.
+ *
+ * Buffers can require an additional descriptor to send their planes array, and
+ * can have pointers to userspace memory hence this dedicated function.
+ */
+static int virtio_media_send_buffer_ioctl(struct v4l2_fh *fh, u32 ioctl,
+					  struct v4l2_buffer *b)
+{
+	struct video_device *video_dev = fh->vdev;
+	struct virtio_media *vv = to_virtio_media(video_dev);
+	struct virtio_media_session *session = fh_to_session(fh);
+	struct v4l2_plane *orig_planes = NULL;
+	struct scatterlist *sgs[64];
+	/*
+	 * End of the device-readable buffer SGs, to reuse in device-writable
+	 * section.
+	 */
+	size_t num_cmd_sgs;
+	size_t end_buf_sg;
+	struct scatterlist_builder builder = {
+		.descs = session->command_sgs.sgl,
+		.num_descs = DESC_CHAIN_MAX_LEN,
+		.cur_desc = 0,
+		.shadow_buffer = session->shadow_buf,
+		.shadow_buffer_size = VIRTIO_SHADOW_BUF_SIZE,
+		.shadow_buffer_pos = 0,
+		.sgs = sgs,
+		.num_sgs = ARRAY_SIZE(sgs),
+		.cur_sg = 0,
+	};
+	size_t resp_len;
+	int ret;
+	int i;
+
+	if (b->type > VIRTIO_MEDIA_LAST_QUEUE)
+		return -EINVAL;
+
+	if (V4L2_TYPE_IS_MULTIPLANAR(b->type))
+		orig_planes = b->m.planes;
+
+	/* Command descriptor */
+	ret = scatterlist_builder_add_ioctl_cmd(&builder, session, ioctl);
+	if (ret)
+		return ret;
+
+	/* Command payload (struct v4l2_buffer) */
+	ret = scatterlist_builder_add_buffer(&builder, b);
+	if (ret < 0)
+		return ret;
+
+	end_buf_sg = builder.cur_sg;
+	num_cmd_sgs = builder.cur_sg;
+
+	/* Response descriptor */
+	ret = scatterlist_builder_add_ioctl_resp(&builder, session);
+	if (ret)
+		return ret;
+
+	/* Response payload (same as input, but no userptr mapping) */
+	for (i = 1; i < end_buf_sg; i++) {
+		ret = scatterlist_builder_add_descriptor(&builder, i);
+		if (ret < 0)
+			return ret;
+	}
+
+	ret = virtio_media_send_command(vv, builder.sgs, num_cmd_sgs,
+					builder.cur_sg - num_cmd_sgs,
+					sizeof(struct virtio_media_resp_ioctl) +
+					sizeof(*b), &resp_len);
+	if (ret < 0)
+		return ret;
+
+	resp_len -= sizeof(struct virtio_media_resp_ioctl);
+
+	/* Make sure that the reply length covers our v4l2_buffer */
+	if (resp_len < sizeof(*b))
+		return -EINVAL;
+
+	ret = scatterlist_builder_retrieve_buffer(&builder, num_cmd_sgs + 1, b,
+						  orig_planes);
+	if (ret) {
+		v4l2_err(&vv->v4l2_dev,
+			 "failed to retrieve response descriptor chain\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+/**
+ * virtio_media_send_ext_controls_ioctl() - Send an ioctl taking extended
+ * controls as parameters to the device.
+ * @fh: file handler of the session doing the ioctl.
+ * @ioctl: ``VIDIOC_*`` ioctl code.
+ * @ctrls: &struct v4l2_ext_controls to be sent as the ioctl payload.
+ *
+ * Queues an ioctl that sends a &struct v4l2_ext_controls to the host and
+ * receives an updated version.
+ *
+ * &struct v4l2_ext_controls has a pointer to an array of
+ * &struct v4l2_ext_control, and also potentially pointers to user-space memory
+ * that we need to map properly, hence the dedicated function.
+ */
+static int virtio_media_send_ext_controls_ioctl(struct v4l2_fh *fh, u32 ioctl,
+						struct v4l2_ext_controls *ctrls)
+{
+	struct video_device *video_dev = fh->vdev;
+	struct virtio_media *vv = to_virtio_media(video_dev);
+	struct virtio_media_session *session = fh_to_session(fh);
+	size_t num_cmd_sgs;
+	size_t end_ctrls_sg;
+	struct v4l2_ext_control *controls_backup = ctrls->controls;
+	const u32 num_ctrls = ctrls->count;
+	struct scatterlist *sgs[64];
+	struct scatterlist_builder builder = {
+		.descs = session->command_sgs.sgl,
+		.num_descs = DESC_CHAIN_MAX_LEN,
+		.cur_desc = 0,
+		.shadow_buffer = session->shadow_buf,
+		.shadow_buffer_size = VIRTIO_SHADOW_BUF_SIZE,
+		.shadow_buffer_pos = 0,
+		.sgs = sgs,
+		.num_sgs = ARRAY_SIZE(sgs),
+		.cur_sg = 0,
+	};
+	size_t resp_len = 0;
+	int i;
+
+	/* Command descriptor */
+	int ret = scatterlist_builder_add_ioctl_cmd(&builder, session, ioctl);
+
+	if (ret)
+		return ret;
+
+	/* v4l2_controls */
+	ret = scatterlist_builder_add_ext_ctrls(&builder, ctrls);
+	if (ret)
+		return ret;
+
+	end_ctrls_sg = builder.cur_sg;
+
+	ret = scatterlist_builder_add_ext_ctrls_userptrs(&builder, ctrls);
+	if (ret)
+		return ret;
+
+	num_cmd_sgs = builder.cur_sg;
+
+	/* Response descriptor */
+	ret = scatterlist_builder_add_ioctl_resp(&builder, session);
+	if (ret)
+		return ret;
+
+	/* Response payload (same as input but without userptrs) */
+	for (i = 1; i < end_ctrls_sg; i++) {
+		ret = scatterlist_builder_add_descriptor(&builder, i);
+		if (ret < 0)
+			return ret;
+	}
+
+	ret = virtio_media_send_command(vv, builder.sgs, num_cmd_sgs,
+					builder.cur_sg - num_cmd_sgs,
+					sizeof(struct virtio_media_resp_ioctl) +
+					sizeof(*ctrls),
+					&resp_len);
+
+	/* Just in case the host touched these. */
+	ctrls->controls = controls_backup;
+	if (ctrls->count != num_ctrls) {
+		v4l2_err(&vv->v4l2_dev,
+			 "device returned a number of controls different than the one submitted\n");
+	}
+	if (ctrls->count > num_ctrls)
+		return -ENOSPC;
+
+	/*
+	 * Even if we have received an error, we may need to read our payload
+	 * back.
+	 */
+	if (ret < 0 && resp_len >= sizeof(struct virtio_media_resp_ioctl) +
+					   sizeof(*ctrls)) {
+		/*
+		 * Deliberately ignore the error here as we want to return the
+		 * previous one.
+		 */
+		scatterlist_builder_retrieve_ext_ctrls(&builder,
+						       num_cmd_sgs + 1, ctrls);
+		return ret;
+	}
+
+	resp_len -= sizeof(struct virtio_media_resp_ioctl);
+
+	/* Make sure that the reply's length covers our v4l2_ext_controls */
+	if (resp_len < sizeof(*ctrls))
+		return -EINVAL;
+
+	ret = scatterlist_builder_retrieve_ext_ctrls(&builder, num_cmd_sgs + 1,
+						     ctrls);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+/**
+ * virtio_media_clear_queue() - clear all pending buffers on a streamed-off
+ *                              queue.
+ * @session: session which the queue to clear belongs to.
+ * @queue: state of the queue to clear.
+ *
+ * Helper function to clear the list of buffers waiting to be dequeued on a
+ * queue that has just been streamed off.
+ */
+static void virtio_media_clear_queue(struct virtio_media_session *session,
+				     struct virtio_media_queue_state *queue)
+{
+	struct list_head *p, *n;
+	int i;
+
+	mutex_lock(&session->queues_lock);
+
+	list_for_each_safe(p, n, &queue->pending_dqbufs) {
+		struct virtio_media_buffer *dqbuf =
+			list_entry(p, struct virtio_media_buffer, list);
+
+		list_del(&dqbuf->list);
+	}
+
+	/* All buffers are now dequeued. */
+	for (i = 0; i < queue->allocated_bufs; i++)
+		queue->buffers[i].buffer.flags = 0;
+
+	queue->queued_bufs = 0;
+	queue->streaming = false;
+	queue->is_capture_last = false;
+
+	mutex_unlock(&session->queues_lock);
+}
+
+/*
+ * Macros suitable for defining ioctls with a constant size payload.
+ */
+
+#define SIMPLE_WR_IOCTL(name, ioctl, payload_t)                       \
+	static int virtio_media_##name(struct file *file, void *fh,   \
+				       payload_t *payload)            \
+	{                                                             \
+		struct v4l2_fh *vfh = file_to_v4l2_fh(file);          \
+		return virtio_media_send_wr_ioctl(vfh, ioctl, payload,\
+						  sizeof(*payload),   \
+						  sizeof(*payload));  \
+	}
+#define SIMPLE_R_IOCTL(name, ioctl, payload_t)                       \
+	static int virtio_media_##name(struct file *file, void *fh,  \
+				       payload_t *payload)           \
+	{                                                            \
+		struct v4l2_fh *vfh = file_to_v4l2_fh(file);         \
+		return virtio_media_send_r_ioctl(vfh, ioctl, payload,\
+						 sizeof(*payload));  \
+	}
+#define SIMPLE_W_IOCTL(name, ioctl, payload_t)                       \
+	static int virtio_media_##name(struct file *file, void *fh,  \
+				       payload_t *payload)           \
+	{                                                            \
+		struct v4l2_fh *vfh = file_to_v4l2_fh(file);         \
+		return virtio_media_send_w_ioctl(vfh, ioctl, payload,\
+						 sizeof(*payload));  \
+	}
+
+/*
+ * V4L2 ioctl handlers.
+ *
+ * Most of these functions just forward the ioctl to the host, for these we can
+ * use one of the SIMPLE_*_IOCTL macros. Exceptions that have their own
+ * standalone function follow.
+ */
+
+SIMPLE_WR_IOCTL(enum_fmt, VIDIOC_ENUM_FMT, struct v4l2_fmtdesc)
+SIMPLE_WR_IOCTL(g_fmt, VIDIOC_G_FMT, struct v4l2_format)
+SIMPLE_WR_IOCTL(s_fmt, VIDIOC_S_FMT, struct v4l2_format)
+SIMPLE_WR_IOCTL(try_fmt, VIDIOC_TRY_FMT, struct v4l2_format)
+SIMPLE_WR_IOCTL(enum_framesizes, VIDIOC_ENUM_FRAMESIZES,
+		struct v4l2_frmsizeenum)
+SIMPLE_WR_IOCTL(enum_frameintervals, VIDIOC_ENUM_FRAMEINTERVALS,
+		struct v4l2_frmivalenum)
+SIMPLE_WR_IOCTL(query_ext_ctrl, VIDIOC_QUERY_EXT_CTRL,
+		struct v4l2_query_ext_ctrl)
+SIMPLE_WR_IOCTL(s_dv_timings, VIDIOC_S_DV_TIMINGS, struct v4l2_dv_timings)
+SIMPLE_WR_IOCTL(g_dv_timings, VIDIOC_G_DV_TIMINGS, struct v4l2_dv_timings)
+SIMPLE_R_IOCTL(query_dv_timings, VIDIOC_QUERY_DV_TIMINGS,
+	       struct v4l2_dv_timings)
+SIMPLE_WR_IOCTL(enum_dv_timings, VIDIOC_ENUM_DV_TIMINGS,
+		struct v4l2_enum_dv_timings)
+SIMPLE_WR_IOCTL(dv_timings_cap, VIDIOC_DV_TIMINGS_CAP,
+		struct v4l2_dv_timings_cap)
+SIMPLE_WR_IOCTL(enuminput, VIDIOC_ENUMINPUT, struct v4l2_input)
+SIMPLE_WR_IOCTL(querymenu, VIDIOC_QUERYMENU, struct v4l2_querymenu)
+SIMPLE_WR_IOCTL(enumoutput, VIDIOC_ENUMOUTPUT, struct v4l2_output)
+SIMPLE_WR_IOCTL(enumaudio, VIDIOC_ENUMAUDIO, struct v4l2_audio)
+SIMPLE_R_IOCTL(g_audio, VIDIOC_G_AUDIO, struct v4l2_audio)
+SIMPLE_W_IOCTL(s_audio, VIDIOC_S_AUDIO, const struct v4l2_audio)
+SIMPLE_WR_IOCTL(enumaudout, VIDIOC_ENUMAUDOUT, struct v4l2_audioout)
+SIMPLE_R_IOCTL(g_audout, VIDIOC_G_AUDOUT, struct v4l2_audioout)
+SIMPLE_W_IOCTL(s_audout, VIDIOC_S_AUDOUT, const struct v4l2_audioout)
+SIMPLE_WR_IOCTL(g_modulator, VIDIOC_G_MODULATOR, struct v4l2_modulator)
+SIMPLE_W_IOCTL(s_modulator, VIDIOC_S_MODULATOR, const struct v4l2_modulator)
+SIMPLE_WR_IOCTL(g_selection, VIDIOC_G_SELECTION, struct v4l2_selection)
+SIMPLE_WR_IOCTL(s_selection, VIDIOC_S_SELECTION, struct v4l2_selection)
+SIMPLE_R_IOCTL(g_enc_index, VIDIOC_G_ENC_INDEX, struct v4l2_enc_idx)
+SIMPLE_WR_IOCTL(encoder_cmd, VIDIOC_ENCODER_CMD, struct v4l2_encoder_cmd)
+SIMPLE_WR_IOCTL(try_encoder_cmd, VIDIOC_TRY_ENCODER_CMD,
+		struct v4l2_encoder_cmd)
+SIMPLE_WR_IOCTL(try_decoder_cmd, VIDIOC_TRY_DECODER_CMD,
+		struct v4l2_decoder_cmd)
+SIMPLE_WR_IOCTL(g_parm, VIDIOC_G_PARM, struct v4l2_streamparm)
+SIMPLE_WR_IOCTL(s_parm, VIDIOC_S_PARM, struct v4l2_streamparm)
+SIMPLE_R_IOCTL(g_std, VIDIOC_G_STD, v4l2_std_id)
+SIMPLE_R_IOCTL(querystd, VIDIOC_QUERYSTD, v4l2_std_id)
+SIMPLE_WR_IOCTL(enumstd, VIDIOC_ENUMSTD, struct v4l2_standard)
+SIMPLE_WR_IOCTL(g_tuner, VIDIOC_G_TUNER, struct v4l2_tuner)
+SIMPLE_W_IOCTL(s_tuner, VIDIOC_S_TUNER, const struct v4l2_tuner)
+SIMPLE_WR_IOCTL(g_frequency, VIDIOC_G_FREQUENCY, struct v4l2_frequency)
+SIMPLE_W_IOCTL(s_frequency, VIDIOC_S_FREQUENCY, const struct v4l2_frequency)
+SIMPLE_WR_IOCTL(enum_freq_bands, VIDIOC_ENUM_FREQ_BANDS,
+		struct v4l2_frequency_band)
+SIMPLE_WR_IOCTL(g_sliced_vbi_cap, VIDIOC_G_SLICED_VBI_CAP,
+		struct v4l2_sliced_vbi_cap)
+SIMPLE_W_IOCTL(s_hw_freq_seek, VIDIOC_S_HW_FREQ_SEEK,
+	       const struct v4l2_hw_freq_seek)
+
+/*
+ * QUERYCAP is handled by reading the configuration area.
+ */
+
+static int virtio_media_querycap(struct file *file, void *fh,
+				 struct v4l2_capability *cap)
+{
+	struct video_device *video_dev = video_devdata(file);
+	struct virtio_media *vv = to_virtio_media(video_dev);
+
+	strscpy(cap->bus_info, "platform:virtio-media");
+	strscpy(cap->driver, VIRTIO_MEDIA_DEFAULT_DRIVER_NAME);
+
+	virtio_cread_bytes(vv->virtio_dev, 8, cap->card, sizeof(cap->card));
+
+	cap->capabilities = video_dev->device_caps | V4L2_CAP_DEVICE_CAPS;
+	cap->device_caps = video_dev->device_caps;
+
+	return 0;
+}
+
+/*
+ * Extended control ioctls are handled mostly identically.
+ */
+
+static int virtio_media_g_ext_ctrls(struct file *file, void *fh,
+				    struct v4l2_ext_controls *ctrls)
+{
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
+
+	return virtio_media_send_ext_controls_ioctl(vfh, VIDIOC_G_EXT_CTRLS,
+						    ctrls);
+}
+
+static int virtio_media_s_ext_ctrls(struct file *file, void *fh,
+				    struct v4l2_ext_controls *ctrls)
+{
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
+
+	return virtio_media_send_ext_controls_ioctl(vfh, VIDIOC_S_EXT_CTRLS,
+						    ctrls);
+}
+
+static int virtio_media_try_ext_ctrls(struct file *file, void *fh,
+				      struct v4l2_ext_controls *ctrls)
+{
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
+
+	return virtio_media_send_ext_controls_ioctl(vfh, VIDIOC_TRY_EXT_CTRLS,
+						    ctrls);
+}
+
+/*
+ * Subscribe/unsubscribe from an event.
+ */
+
+static int
+virtio_media_subscribe_event(struct v4l2_fh *fh,
+			     const struct v4l2_event_subscription *sub)
+{
+	struct video_device *video_dev = fh->vdev;
+	struct virtio_media *vv = to_virtio_media(video_dev);
+	int ret;
+
+	/* First subscribe to the event in the guest. */
+	switch (sub->type) {
+	case V4L2_EVENT_SOURCE_CHANGE:
+		ret = v4l2_src_change_event_subscribe(fh, sub);
+		break;
+	default:
+		ret = v4l2_event_subscribe(fh, sub, 1, NULL);
+		break;
+	}
+	if (ret)
+		return ret;
+
+	/* Then ask the host to signal us these events. */
+	ret = virtio_media_send_w_ioctl(fh, VIDIOC_SUBSCRIBE_EVENT, sub,
+					sizeof(*sub));
+	if (ret < 0) {
+		v4l2_event_unsubscribe(fh, sub);
+		return ret;
+	}
+
+	/*
+	 * Subscribing to an event may result in that event being signaled
+	 * immediately. Process all pending events to make sure we don't
+	 * miss it.
+	 */
+	if (sub->flags & V4L2_EVENT_SUB_FL_SEND_INITIAL)
+		virtio_media_process_events(vv);
+
+	return 0;
+}
+
+static int
+virtio_media_unsubscribe_event(struct v4l2_fh *fh,
+			       const struct v4l2_event_subscription *sub)
+{
+	int ret = virtio_media_send_w_ioctl(fh, VIDIOC_UNSUBSCRIBE_EVENT, sub,
+					sizeof(*sub));
+	if (ret < 0)
+		return ret;
+
+	ret = v4l2_event_unsubscribe(fh, sub);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+/*
+ * Streamon/off affect the local queue state.
+ */
+
+static int virtio_media_streamon(struct file *file, void *fh,
+				 enum v4l2_buf_type i)
+{
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
+	struct virtio_media_session *session = fh_to_session(vfh);
+	int ret;
+
+	if (i > VIRTIO_MEDIA_LAST_QUEUE)
+		return -EINVAL;
+
+	ret = virtio_media_send_w_ioctl(vfh, VIDIOC_STREAMON, &i, sizeof(i));
+	if (ret < 0)
+		return ret;
+
+	session->queues[i].streaming = true;
+
+	return 0;
+}
+
+static int virtio_media_streamoff(struct file *file, void *fh,
+				  enum v4l2_buf_type i)
+{
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
+	struct virtio_media_session *session = fh_to_session(vfh);
+	int ret;
+
+	if (i > VIRTIO_MEDIA_LAST_QUEUE)
+		return -EINVAL;
+
+	ret = virtio_media_send_w_ioctl(vfh, VIDIOC_STREAMOFF, &i, sizeof(i));
+	if (ret < 0)
+		return ret;
+
+	virtio_media_clear_queue(session, &session->queues[i]);
+
+	return 0;
+}
+
+/*
+ * Buffer creation/queuing functions deal with the local driver state.
+ */
+
+static int virtio_media_reqbufs(struct file *file, void *fh,
+				struct v4l2_requestbuffers *b)
+{
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
+	struct virtio_media_session *session = fh_to_session(vfh);
+	struct virtio_media_queue_state *queue;
+	int ret;
+
+	if (b->type > VIRTIO_MEDIA_LAST_QUEUE)
+		return -EINVAL;
+
+	if (b->memory == V4L2_MEMORY_USERPTR)
+		return -EINVAL;
+
+	ret = virtio_media_send_wr_ioctl(vfh, VIDIOC_REQBUFS, b, sizeof(*b),
+					 sizeof(*b));
+	if (ret)
+		return ret;
+
+	queue = &session->queues[b->type];
+
+	/* REQBUFS(0) is an implicit STREAMOFF. */
+	if (b->count == 0)
+		virtio_media_clear_queue(session, queue);
+
+	vfree(queue->buffers);
+	queue->buffers = NULL;
+
+	if (b->count > 0) {
+		queue->buffers =
+			vzalloc(sizeof(struct virtio_media_buffer) * b->count);
+		if (!queue->buffers)
+			return -ENOMEM;
+	}
+
+	queue->allocated_bufs = b->count;
+
+	/*
+	 * If a multiplanar queue is successfully used here, this means
+	 * we are using the multiplanar interface.
+	 */
+	if (V4L2_TYPE_IS_MULTIPLANAR(b->type))
+		session->uses_mplane = true;
+
+	b->capabilities &= ~V4L2_BUF_CAP_SUPPORTS_USERPTR;
+
+	/* We do not support DMABUF yet. */
+	b->capabilities &= ~V4L2_BUF_CAP_SUPPORTS_DMABUF;
+
+	return 0;
+}
+
+static int virtio_media_querybuf(struct file *file, void *fh,
+				 struct v4l2_buffer *b)
+{
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
+	struct virtio_media_session *session = fh_to_session(vfh);
+	struct virtio_media_queue_state *queue;
+	struct virtio_media_buffer *buffer;
+
+	int ret = virtio_media_send_buffer_ioctl(vfh, VIDIOC_QUERYBUF, b);
+
+	if (ret)
+		return ret;
+
+	if (b->type > VIRTIO_MEDIA_LAST_QUEUE)
+		return -EINVAL;
+
+	queue = &session->queues[b->type];
+	if (b->index >= queue->allocated_bufs)
+		return -EINVAL;
+
+	buffer = &queue->buffers[b->index];
+	/*
+	 * Set the DONE flag if the buffer is waiting in our own dequeue
+	 * queue.
+	 */
+	b->flags |= (buffer->buffer.flags & V4L2_BUF_FLAG_DONE);
+
+	return 0;
+}
+
+static int virtio_media_create_bufs(struct file *file, void *fh,
+				    struct v4l2_create_buffers *b)
+{
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
+	struct virtio_media_session *session = fh_to_session(vfh);
+	struct virtio_media_queue_state *queue;
+	struct virtio_media_buffer *buffers;
+	u32 type = b->format.type;
+	int ret;
+
+	if (type > VIRTIO_MEDIA_LAST_QUEUE)
+		return -EINVAL;
+
+	queue = &session->queues[type];
+
+	ret = virtio_media_send_wr_ioctl(vfh, VIDIOC_CREATE_BUFS, b, sizeof(*b),
+					 sizeof(*b));
+	if (ret)
+		return ret;
+
+	/* If count is zero, we were just checking for format. */
+	if (b->count == 0)
+		return 0;
+
+	buffers = queue->buffers;
+
+	queue->buffers =
+		vzalloc(sizeof(*queue->buffers) * (b->index + b->count));
+	if (!queue->buffers) {
+		queue->buffers = buffers;
+		return -ENOMEM;
+	}
+
+	memcpy(queue->buffers, buffers,
+	       sizeof(*buffers) * queue->allocated_bufs);
+	vfree(buffers);
+
+	queue->allocated_bufs = b->index + b->count;
+
+	return 0;
+}
+
+static int virtio_media_prepare_buf(struct file *file, void *fh,
+				    struct v4l2_buffer *b)
+{
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
+	struct virtio_media_session *session = fh_to_session(vfh);
+	struct virtio_media_queue_state *queue;
+	struct virtio_media_buffer *buffer;
+	int i, ret;
+
+	if (b->type > VIRTIO_MEDIA_LAST_QUEUE)
+		return -EINVAL;
+	queue = &session->queues[b->type];
+	if (b->index >= queue->allocated_bufs)
+		return -EINVAL;
+	buffer = &queue->buffers[b->index];
+
+	buffer->buffer.m = b->m;
+	if (V4L2_TYPE_IS_MULTIPLANAR(b->type)) {
+		if (b->length > VIDEO_MAX_PLANES)
+			return -EINVAL;
+		for (i = 0; i < b->length; i++)
+			buffer->planes[i].m = b->m.planes[i].m;
+	}
+
+	ret = virtio_media_send_buffer_ioctl(vfh, VIDIOC_PREPARE_BUF, b);
+	if (ret)
+		return ret;
+
+	buffer->buffer.flags = V4L2_BUF_FLAG_PREPARED;
+
+	return 0;
+}
+
+static int virtio_media_qbuf(struct file *file, void *fh, struct v4l2_buffer *b)
+{
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
+	struct virtio_media_session *session = fh_to_session(vfh);
+	struct virtio_media_queue_state *queue;
+	struct virtio_media_buffer *buffer;
+	bool prepared;
+	u32 old_flags;
+	int i, ret;
+
+	if (b->type > VIRTIO_MEDIA_LAST_QUEUE)
+		return -EINVAL;
+	queue = &session->queues[b->type];
+	if (b->index >= queue->allocated_bufs)
+		return -EINVAL;
+	buffer = &queue->buffers[b->index];
+	prepared = buffer->buffer.flags & V4L2_BUF_FLAG_PREPARED;
+
+	/*
+	 * Store the buffer and plane `m` information so we can retrieve
+	 * it again when DQBUF occurs.
+	 */
+	if (!prepared) {
+		buffer->buffer.m = b->m;
+		if (V4L2_TYPE_IS_MULTIPLANAR(b->type)) {
+			if (b->length > VIDEO_MAX_PLANES)
+				return -EINVAL;
+			for (i = 0; i < b->length; i++)
+				buffer->planes[i].m = b->m.planes[i].m;
+		}
+	}
+	old_flags = buffer->buffer.flags;
+	buffer->buffer.flags = V4L2_BUF_FLAG_QUEUED;
+
+	ret = virtio_media_send_buffer_ioctl(vfh, VIDIOC_QBUF, b);
+	if (ret) {
+		/* Rollback the previous flags as the buffer is not queued. */
+		buffer->buffer.flags = old_flags;
+		return ret;
+	}
+
+	queue->queued_bufs += 1;
+
+	return 0;
+}
+
+static int virtio_media_dqbuf(struct file *file, void *fh,
+			      struct v4l2_buffer *b)
+{
+	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_to_v4l2_fh(file));
+	struct virtio_media_buffer *dqbuf;
+	struct virtio_media_queue_state *queue;
+	struct list_head *buffer_queue;
+	struct v4l2_plane *planes_backup = NULL;
+	const bool is_multiplanar = V4L2_TYPE_IS_MULTIPLANAR(b->type);
+	int ret;
+
+	if (b->type > VIRTIO_MEDIA_LAST_QUEUE)
+		return -EINVAL;
+
+	queue = &session->queues[b->type];
+
+	/*
+	 * If a buffer with the LAST flag has been returned, subsequent
+	 * calls to DQBUF must return -EPIPE until the queue is cleared.
+	 */
+	if (queue->is_capture_last)
+		return -EPIPE;
+
+	buffer_queue = &queue->pending_dqbufs;
+
+	if (session->nonblocking_dequeue) {
+		if (list_empty(buffer_queue))
+			return -EAGAIN;
+	} else if (queue->allocated_bufs == 0) {
+		return -EINVAL;
+	} else if (!queue->streaming) {
+		return -EINVAL;
+	}
+
+	/*
+	 * vv->lock has been acquired by virtio_media_device_ioctl. Release it
+	 * while we wait so that other ioctls for this session can be processed
+	 * and potentially trigger dqbuf_wait.
+	 */
+	mutex_unlock(&vv->vlock);
+	ret = wait_event_interruptible(session->dqbuf_wait,
+				       !list_empty(buffer_queue));
+	mutex_lock(&vv->vlock);
+	if (ret)
+		return -EINTR;
+
+	mutex_lock(&session->queues_lock);
+	dqbuf = list_first_entry(buffer_queue, struct virtio_media_buffer,
+				 list);
+	list_del(&dqbuf->list);
+	mutex_unlock(&session->queues_lock);
+
+	/* Clear the DONE flag as the buffer is now being dequeued. */
+	dqbuf->buffer.flags &= ~V4L2_BUF_FLAG_DONE;
+
+	if (is_multiplanar) {
+		size_t nb_planes = min_t(u32, b->length, VIDEO_MAX_PLANES);
+
+		memcpy(b->m.planes, dqbuf->planes,
+		       nb_planes * sizeof(struct v4l2_plane));
+		planes_backup = b->m.planes;
+	}
+
+	memcpy(b, &dqbuf->buffer, sizeof(*b));
+
+	if (is_multiplanar)
+		b->m.planes = planes_backup;
+
+	if (V4L2_TYPE_IS_CAPTURE(b->type) && b->flags & V4L2_BUF_FLAG_LAST)
+		queue->is_capture_last = true;
+
+	return 0;
+}
+
+/*
+ * s/g_input/output work with an unsigned int - recast this to a u32 so the
+ * size is unambiguous.
+ */
+
+static int virtio_media_g_input(struct file *file, void *fh, unsigned int *i)
+{
+	u32 input;
+
+	int ret = virtio_media_send_wr_ioctl(file_to_v4l2_fh(file),
+					 VIDIOC_G_INPUT, &input,
+					 sizeof(input), sizeof(input));
+	if (ret)
+		return ret;
+
+	*i = input;
+
+	return 0;
+}
+
+static int virtio_media_s_input(struct file *file, void *fh, unsigned int i)
+{
+	u32 input = i;
+
+	return virtio_media_send_wr_ioctl(file_to_v4l2_fh(file),
+					  VIDIOC_S_INPUT, &input,
+					  sizeof(input), sizeof(input));
+}
+
+static int virtio_media_g_output(struct file *file, void *fh, unsigned int *o)
+{
+	u32 output;
+
+	int ret = virtio_media_send_wr_ioctl(file_to_v4l2_fh(file),
+					 VIDIOC_G_OUTPUT, &output,
+					 sizeof(output), sizeof(output));
+	if (ret)
+		return ret;
+
+	*o = output;
+
+	return 0;
+}
+
+static int virtio_media_s_output(struct file *file, void *fh, unsigned int o)
+{
+	u32 output = o;
+
+	return virtio_media_send_wr_ioctl(file_to_v4l2_fh(file),
+					  VIDIOC_S_OUTPUT, &output,
+					  sizeof(output), sizeof(output));
+}
+
+/*
+ * decoder_cmd can affect the state of the CAPTURE queue.
+ */
+
+static int virtio_media_decoder_cmd(struct file *file, void *fh,
+				    struct v4l2_decoder_cmd *cmd)
+{
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
+	struct virtio_media_session *session = fh_to_session(vfh);
+
+	int ret = virtio_media_send_wr_ioctl(vfh, VIDIOC_DECODER_CMD, cmd,
+					 sizeof(*cmd), sizeof(*cmd));
+	if (ret)
+		return ret;
+
+	/* A START command makes the CAPTURE queue able to dequeue again. */
+	if (cmd->cmd == V4L2_DEC_CMD_START) {
+		session->queues[V4L2_BUF_TYPE_VIDEO_CAPTURE].is_capture_last =
+			false;
+		session->queues[V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE]
+			.is_capture_last = false;
+	}
+
+	return 0;
+}
+
+/*
+ * s_std doesn't work with a pointer, so we cannot use SIMPLE_W_IOCTL.
+ */
+
+static int virtio_media_s_std(struct file *file, void *fh, v4l2_std_id s)
+{
+	int ret = virtio_media_send_w_ioctl(file_to_v4l2_fh(file), VIDIOC_S_STD,
+					&s, sizeof(s));
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+const struct v4l2_ioctl_ops virtio_media_ioctl_ops = {
+	/* VIDIOC_QUERYCAP handler */
+	.vidioc_querycap = virtio_media_querycap,
+
+	/* VIDIOC_ENUM_FMT handlers */
+	.vidioc_enum_fmt_vid_cap = virtio_media_enum_fmt,
+	.vidioc_enum_fmt_vid_overlay = virtio_media_enum_fmt,
+	.vidioc_enum_fmt_vid_out = virtio_media_enum_fmt,
+	.vidioc_enum_fmt_sdr_cap = virtio_media_enum_fmt,
+	.vidioc_enum_fmt_sdr_out = virtio_media_enum_fmt,
+	.vidioc_enum_fmt_meta_cap = virtio_media_enum_fmt,
+	.vidioc_enum_fmt_meta_out = virtio_media_enum_fmt,
+
+	/* VIDIOC_G_FMT handlers */
+	.vidioc_g_fmt_vid_cap = virtio_media_g_fmt,
+	.vidioc_g_fmt_vid_overlay = virtio_media_g_fmt,
+	.vidioc_g_fmt_vid_out = virtio_media_g_fmt,
+	.vidioc_g_fmt_vid_out_overlay = virtio_media_g_fmt,
+	.vidioc_g_fmt_vbi_cap = virtio_media_g_fmt,
+	.vidioc_g_fmt_vbi_out = virtio_media_g_fmt,
+	.vidioc_g_fmt_sliced_vbi_cap = virtio_media_g_fmt,
+	.vidioc_g_fmt_sliced_vbi_out = virtio_media_g_fmt,
+	.vidioc_g_fmt_vid_cap_mplane = virtio_media_g_fmt,
+	.vidioc_g_fmt_vid_out_mplane = virtio_media_g_fmt,
+	.vidioc_g_fmt_sdr_cap = virtio_media_g_fmt,
+	.vidioc_g_fmt_sdr_out = virtio_media_g_fmt,
+	.vidioc_g_fmt_meta_cap = virtio_media_g_fmt,
+	.vidioc_g_fmt_meta_out = virtio_media_g_fmt,
+
+	/* VIDIOC_S_FMT handlers */
+	.vidioc_s_fmt_vid_cap = virtio_media_s_fmt,
+	.vidioc_s_fmt_vid_overlay = virtio_media_s_fmt,
+	.vidioc_s_fmt_vid_out = virtio_media_s_fmt,
+	.vidioc_s_fmt_vid_out_overlay = virtio_media_s_fmt,
+	.vidioc_s_fmt_vbi_cap = virtio_media_s_fmt,
+	.vidioc_s_fmt_vbi_out = virtio_media_s_fmt,
+	.vidioc_s_fmt_sliced_vbi_cap = virtio_media_s_fmt,
+	.vidioc_s_fmt_sliced_vbi_out = virtio_media_s_fmt,
+	.vidioc_s_fmt_vid_cap_mplane = virtio_media_s_fmt,
+	.vidioc_s_fmt_vid_out_mplane = virtio_media_s_fmt,
+	.vidioc_s_fmt_sdr_cap = virtio_media_s_fmt,
+	.vidioc_s_fmt_sdr_out = virtio_media_s_fmt,
+	.vidioc_s_fmt_meta_cap = virtio_media_s_fmt,
+	.vidioc_s_fmt_meta_out = virtio_media_s_fmt,
+
+	/* VIDIOC_TRY_FMT handlers */
+	.vidioc_try_fmt_vid_cap = virtio_media_try_fmt,
+	.vidioc_try_fmt_vid_overlay = virtio_media_try_fmt,
+	.vidioc_try_fmt_vid_out = virtio_media_try_fmt,
+	.vidioc_try_fmt_vid_out_overlay = virtio_media_try_fmt,
+	.vidioc_try_fmt_vbi_cap = virtio_media_try_fmt,
+	.vidioc_try_fmt_vbi_out = virtio_media_try_fmt,
+	.vidioc_try_fmt_sliced_vbi_cap = virtio_media_try_fmt,
+	.vidioc_try_fmt_sliced_vbi_out = virtio_media_try_fmt,
+	.vidioc_try_fmt_vid_cap_mplane = virtio_media_try_fmt,
+	.vidioc_try_fmt_vid_out_mplane = virtio_media_try_fmt,
+	.vidioc_try_fmt_sdr_cap = virtio_media_try_fmt,
+	.vidioc_try_fmt_sdr_out = virtio_media_try_fmt,
+	.vidioc_try_fmt_meta_cap = virtio_media_try_fmt,
+	.vidioc_try_fmt_meta_out = virtio_media_try_fmt,
+
+	/* Buffer handlers */
+	.vidioc_reqbufs = virtio_media_reqbufs,
+	.vidioc_querybuf = virtio_media_querybuf,
+	.vidioc_qbuf = virtio_media_qbuf,
+	.vidioc_expbuf = NULL,
+	.vidioc_dqbuf = virtio_media_dqbuf,
+	.vidioc_create_bufs = virtio_media_create_bufs,
+	.vidioc_prepare_buf = virtio_media_prepare_buf,
+	/* Overlay interface not supported yet */
+	.vidioc_overlay = NULL,
+	/* Overlay interface not supported yet */
+	.vidioc_g_fbuf = NULL,
+	/* Overlay interface not supported yet */
+	.vidioc_s_fbuf = NULL,
+
+	/* Stream on/off */
+	.vidioc_streamon = virtio_media_streamon,
+	.vidioc_streamoff = virtio_media_streamoff,
+
+	/* Standard handling */
+	.vidioc_g_std = virtio_media_g_std,
+	.vidioc_s_std = virtio_media_s_std,
+	.vidioc_querystd = virtio_media_querystd,
+
+	/* Input handling */
+	.vidioc_enum_input = virtio_media_enuminput,
+	.vidioc_g_input = virtio_media_g_input,
+	.vidioc_s_input = virtio_media_s_input,
+
+	/* Output handling */
+	.vidioc_enum_output = virtio_media_enumoutput,
+	.vidioc_g_output = virtio_media_g_output,
+	.vidioc_s_output = virtio_media_s_output,
+
+	/* Control handling */
+	.vidioc_query_ext_ctrl = virtio_media_query_ext_ctrl,
+	.vidioc_g_ext_ctrls = virtio_media_g_ext_ctrls,
+	.vidioc_s_ext_ctrls = virtio_media_s_ext_ctrls,
+	.vidioc_try_ext_ctrls = virtio_media_try_ext_ctrls,
+	.vidioc_querymenu = virtio_media_querymenu,
+
+	/* Audio ioctls */
+	.vidioc_enumaudio = virtio_media_enumaudio,
+	.vidioc_g_audio = virtio_media_g_audio,
+	.vidioc_s_audio = virtio_media_s_audio,
+
+	/* Audio out ioctls */
+	.vidioc_enumaudout = virtio_media_enumaudout,
+	.vidioc_g_audout = virtio_media_g_audout,
+	.vidioc_s_audout = virtio_media_s_audout,
+	.vidioc_g_modulator = virtio_media_g_modulator,
+	.vidioc_s_modulator = virtio_media_s_modulator,
+
+	/* Crop ioctls */
+	/*
+	 * Not directly an ioctl (part of VIDIOC_CROPCAP), so no need to
+	 * implement.
+	 */
+	.vidioc_g_pixelaspect = NULL,
+	.vidioc_g_selection = virtio_media_g_selection,
+	.vidioc_s_selection = virtio_media_s_selection,
+
+	/* Compression ioctls */
+	/* Deprecated in V4L2. */
+	.vidioc_g_jpegcomp = NULL,
+	/* Deprecated in V4L2. */
+	.vidioc_s_jpegcomp = NULL,
+	.vidioc_g_enc_index = virtio_media_g_enc_index,
+	.vidioc_encoder_cmd = virtio_media_encoder_cmd,
+	.vidioc_try_encoder_cmd = virtio_media_try_encoder_cmd,
+	.vidioc_decoder_cmd = virtio_media_decoder_cmd,
+	.vidioc_try_decoder_cmd = virtio_media_try_decoder_cmd,
+
+	/* Stream type-dependent parameter ioctls */
+	.vidioc_g_parm = virtio_media_g_parm,
+	.vidioc_s_parm = virtio_media_s_parm,
+
+	/* Tuner ioctls */
+	.vidioc_g_tuner = virtio_media_g_tuner,
+	.vidioc_s_tuner = virtio_media_s_tuner,
+	.vidioc_g_frequency = virtio_media_g_frequency,
+	.vidioc_s_frequency = virtio_media_s_frequency,
+	.vidioc_enum_freq_bands = virtio_media_enum_freq_bands,
+
+	/* Sliced VBI cap */
+	.vidioc_g_sliced_vbi_cap = virtio_media_g_sliced_vbi_cap,
+
+	/* Log status ioctl */
+	/* Guest-only operation */
+	.vidioc_log_status = NULL,
+
+	.vidioc_s_hw_freq_seek = virtio_media_s_hw_freq_seek,
+
+	.vidioc_enum_framesizes = virtio_media_enum_framesizes,
+	.vidioc_enum_frameintervals = virtio_media_enum_frameintervals,
+
+	/* DV Timings IOCTLs */
+	.vidioc_s_dv_timings = virtio_media_s_dv_timings,
+	.vidioc_g_dv_timings = virtio_media_g_dv_timings,
+	.vidioc_query_dv_timings = virtio_media_query_dv_timings,
+	.vidioc_enum_dv_timings = virtio_media_enum_dv_timings,
+	.vidioc_dv_timings_cap = virtio_media_dv_timings_cap,
+	.vidioc_g_edid = NULL,
+	.vidioc_s_edid = NULL,
+
+	.vidioc_subscribe_event = virtio_media_subscribe_event,
+	.vidioc_unsubscribe_event = virtio_media_unsubscribe_event,
+
+	/* For other private ioctls */
+	.vidioc_default = NULL,
+};
+
+long virtio_media_device_ioctl(struct file *file, unsigned int cmd,
+			       unsigned long arg)
+{
+	struct video_device *video_dev = video_devdata(file);
+	struct virtio_media *vv = to_virtio_media(video_dev);
+	struct v4l2_fh *vfh = NULL;
+	struct v4l2_standard standard;
+	v4l2_std_id std_id = 0;
+	int ret;
+
+	if (test_bit(V4L2_FL_USES_V4L2_FH, &video_dev->flags))
+		vfh = file_to_v4l2_fh(file);
+
+	mutex_lock(&vv->vlock);
+
+	/*
+	 * We need to handle a few ioctls manually because their results
+	 * rely on vfd->tvnorms, which is normally updated by the driver
+	 * as S_INPUT is called. Since we want to just pass these ioctls
+	 * through, we have to hijack them from here.
+	 */
+	switch (cmd) {
+	case VIDIOC_S_STD:
+		ret = copy_from_user(&std_id, (void __user *)arg,
+				     sizeof(std_id));
+		if (ret) {
+			ret = -EINVAL;
+			break;
+		}
+		ret = virtio_media_s_std(file, vfh, std_id);
+		break;
+	case VIDIOC_ENUMSTD:
+		ret = copy_from_user(&standard, (void __user *)arg,
+				     sizeof(standard));
+		if (ret) {
+			ret = -EINVAL;
+			break;
+		}
+		ret = virtio_media_enumstd(file, vfh, &standard);
+		if (ret)
+			break;
+		ret = copy_to_user((void __user *)arg, &standard,
+				   sizeof(standard));
+		if (ret)
+			ret = -EINVAL;
+		break;
+	case VIDIOC_QUERYSTD:
+		ret = virtio_media_querystd(file, vfh, &std_id);
+		if (ret)
+			break;
+		ret = copy_to_user((void __user *)arg, &std_id, sizeof(std_id));
+		if (ret)
+			ret = -EINVAL;
+		break;
+	default:
+		ret = video_ioctl2(file, cmd, arg);
+		break;
+	}
+
+	mutex_unlock(&vv->vlock);
+
+	return ret;
+}
-- 
2.55.0.229.g6434b31f56-goog