Re: [PATCH v7 1/4] media: virtio: Add skeleton virtio-media driver

[Dorinda Bassey]

> From: Alexandre Courbot <gnurou@xxxxxxxxx>
> This patch adds a minimum viable virtio-media driver that binds to the
> virtio device and registers a V4L2 device and a video device, but lacks
> any actual functionality.
> It adds the UAPI header defining the protocol, internal driver headers,
> Kconfig and Makefile entries, and MAINTAINERS entry. Many of the structs
> in the protocol add reserved bits. These are present to ensure 64-bit
> alignment. They are not intended to be used as reserved expansion for
> the protocol in the future, so more reserved space is not required.
> 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>


Reviewed-by: Dorinda Bassey <dbassey@xxxxxxxxxx>
Tested-by: Dorinda Bassey <dbassey@xxxxxxxxxx>

Thanks!


On Thu, Aug 13, 2026 at 8:00 PM Brian Daniels <briandaniels@xxxxxxxxxx> wrote:
>
> From: Alexandre Courbot <gnurou@xxxxxxxxx>
>
> This patch adds a minimum viable virtio-media driver that binds to the
> virtio device and registers a V4L2 device and a video device, but lacks
> any actual functionality.
>
> It adds the UAPI header defining the protocol, internal driver headers,
> Kconfig and Makefile entries, and MAINTAINERS entry. Many of the structs
> in the protocol add reserved bits. These are present to ensure 64-bit
> alignment. They are not intended to be used as reserved expansion for
> the protocol in the future, so more reserved space is not required.
>
> 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>
> ---
>  MAINTAINERS                                |   8 +
>  drivers/media/Kconfig                      |  13 +
>  drivers/media/Makefile                     |   2 +
>  drivers/media/virtio/Makefile              |   7 +
>  drivers/media/virtio/virtio_media.h        |  95 +++++++
>  drivers/media/virtio/virtio_media_driver.c | 146 +++++++++++
>  include/uapi/linux/virtio_media.h          | 287 +++++++++++++++++++++
>  7 files changed, 558 insertions(+)
>  create mode 100644 drivers/media/virtio/Makefile
>  create mode 100644 drivers/media/virtio/virtio_media.h
>  create mode 100644 drivers/media/virtio/virtio_media_driver.c
>  create mode 100644 include/uapi/linux/virtio_media.h
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 3785b8c1d..c3b5c5eb6 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -28573,6 +28573,7 @@ F:      Documentation/devicetree/bindings/virtio/
>  F:     Documentation/driver-api/virtio/
>  F:     drivers/block/virtio_blk.c
>  F:     drivers/crypto/virtio/
> +F:     drivers/media/virtio/
>  F:     drivers/vdpa/
>  F:     drivers/virtio/
>  F:     include/linux/vdpa.h
> @@ -28685,6 +28686,13 @@ S:     Maintained
>  F:     drivers/iommu/virtio-iommu.c
>  F:     include/uapi/linux/virtio_iommu.h
>
> +VIRTIO MEDIA DRIVER
> +M:     Brian Daniels <briandaniels@xxxxxxxxxx>
> +L:     linux-media@xxxxxxxxxxxxxxx
> +S:     Maintained
> +F:     drivers/media/virtio/
> +F:     include/uapi/linux/virtio_media.h
> +
>  VIRTIO MEM DRIVER
>  M:     David Hildenbrand <david@xxxxxxxxxx>
>  L:     virtualization@xxxxxxxxxxxxxxx
> diff --git a/drivers/media/Kconfig b/drivers/media/Kconfig
> index 6abc9302c..ce7d088e7 100644
> --- a/drivers/media/Kconfig
> +++ b/drivers/media/Kconfig
> @@ -136,6 +136,19 @@ config MEDIA_PLATFORM_SUPPORT
>
>           Say Y when you want to be able to see such devices.
>
> +config MEDIA_VIRTIO
> +       tristate "Virtio-media Driver"
> +       depends on VIRTIO && VIDEO_DEV && 64BIT && (X86 || CPU_LITTLE_ENDIAN)
> +       select VIDEOBUF2_CORE
> +       select VIDEOBUF2_MEMOPS
> +       help
> +         Enables the virtio-media driver.
> +
> +         This driver is used to virtualize media devices such as cameras or
> +         decoders from a host into a guest using the V4L2 protocol.
> +
> +         If unsure, say N.
> +
>  config MEDIA_TEST_SUPPORT
>         bool
>         prompt "Test drivers" if MEDIA_SUPPORT_FILTER
> diff --git a/drivers/media/Makefile b/drivers/media/Makefile
> index 20fac24e4..357e786cc 100644
> --- a/drivers/media/Makefile
> +++ b/drivers/media/Makefile
> @@ -23,6 +23,8 @@ obj-$(CONFIG_DVB_CORE) += dvb-core/
>  # There are both core and drivers at RC subtree - merge before drivers
>  obj-y += rc/
>
> +obj-$(CONFIG_MEDIA_VIRTIO) += virtio/
> +
>  obj-$(CONFIG_CEC_CORE) += cec/
>
>  #
> diff --git a/drivers/media/virtio/Makefile b/drivers/media/virtio/Makefile
> new file mode 100644
> index 000000000..09d9834da
> --- /dev/null
> +++ b/drivers/media/virtio/Makefile
> @@ -0,0 +1,7 @@
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# Makefile for the virtio-media device driver.
> +
> +virtio-media-objs := virtio_media_driver.o
> +
> +obj-$(CONFIG_MEDIA_VIRTIO) += virtio-media.o
> diff --git a/drivers/media/virtio/virtio_media.h b/drivers/media/virtio/virtio_media.h
> new file mode 100644
> index 000000000..7acb2b842
> --- /dev/null
> +++ b/drivers/media/virtio/virtio_media.h
> @@ -0,0 +1,95 @@
> +/* SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0+ */
> +
> +/*
> + * Virtio-media structures & functions declarations.
> + *
> + * Copyright (c) 2024-2026 Google LLC.
> + */
> +
> +#ifndef __VIRTIO_MEDIA_H
> +#define __VIRTIO_MEDIA_H
> +
> +#include <linux/virtio_config.h>
> +#include <media/v4l2-device.h>
> +
> +#include "uapi/linux/virtio_media.h"
> +
> +#define DESC_CHAIN_MAX_LEN SG_MAX_SINGLE_ALLOC
> +
> +#define VIRTIO_MEDIA_DEFAULT_DRIVER_NAME "virtio-media"
> +
> +/**
> + * struct virtio_media - Virtio-media device.
> + * @v4l2_dev: v4l2_device for the media device.
> + * @video_dev: video_device for the media device.
> + * @virtio_dev: virtio device for the media device.
> + * @commandq: virtio command queue.
> + * @eventq: virtio event queue.
> + * @eventq_work: work to run when events are received on @eventq.
> + * @mmap_region: region into which MMAP buffers are mapped by the host.
> + * @event_buffer: buffer for event descriptors.
> + * @sessions: list of active sessions on the device.
> + * @sessions_lock: protects @sessions and &struct virtio_media_session.list.
> + * @events_lock: prevents concurrent processing of events.
> + * @cmd: union of the device commands ``open`` and ``munmap``. The other
> + *       commands are handled by &struct virtio_media_session
> + * @resp: union of responses to device commands ``open`` and ``munmap``. The
> + *        other responses are handled by &struct virtio_media_session
> + * @vlock: serializes access to the command queue.
> + * @wq: waitqueue for host responses on the command queue.
> + */
> +struct virtio_media {
> +       struct v4l2_device v4l2_dev;
> +       struct video_device video_dev;
> +
> +       struct virtio_device *virtio_dev;
> +       struct virtqueue *commandq;
> +       struct virtqueue *eventq;
> +       struct work_struct eventq_work;
> +
> +       struct virtio_shm_region mmap_region;
> +
> +       void *event_buffer;
> +
> +       struct list_head sessions;
> +       struct mutex sessions_lock; /* protects sessions list */
> +
> +       struct mutex events_lock; /* prevents concurrent event processing */
> +
> +       __dma_from_device_group_begin();
> +       union {
> +               struct virtio_media_cmd_open open;
> +               struct virtio_media_cmd_munmap munmap;
> +       } cmd;
> +
> +       union {
> +               struct virtio_media_resp_open open;
> +               struct virtio_media_resp_munmap munmap;
> +       } resp;
> +       __dma_from_device_group_end();
> +
> +       struct mutex vlock; /* serializes command queue access */
> +       wait_queue_head_t wq;
> +};
> +
> +static inline struct virtio_media *
> +to_virtio_media(struct video_device *video_dev)
> +{
> +       return container_of(video_dev, struct virtio_media, video_dev);
> +}
> +
> +/* virtio_media_driver.c */
> +
> +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);
> +void virtio_media_process_events(struct virtio_media *vv);
> +
> +/* virtio_media_ioctls.c */
> +
> +long virtio_media_device_ioctl(struct file *file, unsigned int cmd,
> +                              unsigned long arg);
> +extern const struct v4l2_ioctl_ops virtio_media_ioctl_ops;
> +
> +#endif // __VIRTIO_MEDIA_H
> +
> diff --git a/drivers/media/virtio/virtio_media_driver.c b/drivers/media/virtio/virtio_media_driver.c
> new file mode 100644
> index 000000000..25f2ceaa6
> --- /dev/null
> +++ b/drivers/media/virtio/virtio_media_driver.c
> @@ -0,0 +1,146 @@
> +// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0+
> +
> +/*
> + * Virtio-media driver.
> + *
> + * Copyright (c) 2024-2026 Google LLC.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/dev_printk.h>
> +#include <linux/mutex.h>
> +#include <linux/types.h>
> +#include <linux/module.h>
> +#include <linux/virtio.h>
> +#include <linux/virtio_config.h>
> +#include <linux/virtio_ids.h>
> +
> +#include <media/v4l2-dev.h>
> +#include <media/v4l2-device.h>
> +
> +#include "uapi/linux/virtio_media.h"
> +#include "virtio_media.h"
> +
> +static void commandq_callback(struct virtqueue *vq)
> +{
> +}
> +
> +static void eventq_callback(struct virtqueue *vq)
> +{
> +}
> +
> +static const struct v4l2_file_operations virtio_media_fops = {
> +       .owner = THIS_MODULE,
> +       .open = v4l2_fh_open,
> +       .release = v4l2_fh_release,
> +};
> +
> +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 ret;
> +
> +       vv = devm_kzalloc(dev, sizeof(*vv), GFP_KERNEL);
> +       if (!vv)
> +               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];
> +
> +       vd = &vv->video_dev;
> +       vd->v4l2_dev = &vv->v4l2_dev;
> +       vd->vfl_type = VFL_TYPE_VIDEO;
> +       vd->fops = &virtio_media_fops;
> +       vd->release = video_device_release_empty;
> +       strscpy(vd->name, "virtio-media", sizeof(vd->name));
> +
> +       video_set_drvdata(vd, vv);
> +
> +       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_CAP_VIDEO_OUTPUT_MPLANE))
> +               vd->vfl_dir = VFL_DIR_TX;
> +       else
> +               vd->vfl_dir = VFL_DIR_RX;
> +
> +       ret = video_register_device(vd, virtio_cread32(virtio_dev, 4), 0);
> +       if (ret)
> +               goto err_register_device;
> +
> +       virtio_device_ready(virtio_dev);
> +
> +       return 0;
> +
> +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;
> +
> +       virtio_reset_device(virtio_dev);
> +       v4l2_device_unregister(&vv->v4l2_dev);
> +       virtio_dev->config->del_vqs(virtio_dev);
> +       video_unregister_device(&vv->video_dev);
> +}
> +
> +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@xxxxxxxxx>");
> +MODULE_LICENSE("Dual BSD/GPL");
> diff --git a/include/uapi/linux/virtio_media.h b/include/uapi/linux/virtio_media.h
> new file mode 100644
> index 000000000..280fbbe94
> --- /dev/null
> +++ b/include/uapi/linux/virtio_media.h
> @@ -0,0 +1,287 @@
> +/* SPDX-License-Identifier: ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) */
> +
> +/*
> + * Definitions of virtio-media protocol structures.
> + *
> + * Copyright (c) 2024-2026 Google LLC.
> + */
> +
> +#ifndef __VIRTIO_MEDIA_PROTOCOL_H
> +#define __VIRTIO_MEDIA_PROTOCOL_H
> +
> +#include <linux/videodev2.h>
> +
> +/*
> + * Virtio protocol definition.
> + */
> +
> +/**
> + * struct virtio_media_cmd_header - Header for all virtio-media commands.
> + * @cmd: one of VIRTIO_MEDIA_CMD_*.
> + * @__reserved: must be set to zero by the driver.
> + *
> + * This header starts all commands from the driver to the device on the
> + * commandq.
> + */
> +struct virtio_media_cmd_header {
> +       u32 cmd;
> +       u32 __reserved;
> +};
> +
> +/**
> + * struct virtio_media_resp_header - Header for all virtio-media responses.
> + * @status: 0 if the command was successful, or one of the standard Linux error
> + *          codes as a positive integer.
> + * @__reserved: must be set to zero by the device.
> + *
> + * This header starts all responses from the device to the driver on the
> + * commandq.
> + */
> +struct virtio_media_resp_header {
> +       u32 status;
> +       u32 __reserved;
> +};
> +
> +/**
> + * VIRTIO_MEDIA_CMD_OPEN - Command for creating a new session.
> + *
> + * This is the equivalent of calling ``open`` on a V4L2 device node. Upon
> + * success, a session id is returned which can be used to perform other
> + * commands on the session, notably ioctls.
> + */
> +#define VIRTIO_MEDIA_CMD_OPEN 1
> +
> +/**
> + * struct virtio_media_cmd_open - Driver command for VIRTIO_MEDIA_CMD_OPEN.
> + * @hdr: header with cmd member set to VIRTIO_MEDIA_CMD_OPEN.
> + */
> +struct virtio_media_cmd_open {
> +       struct virtio_media_cmd_header hdr;
> +};
> +
> +/**
> + * struct virtio_media_resp_open - Device response for VIRTIO_MEDIA_CMD_OPEN.
> + * @hdr: header containing the status of the command.
> + * @session_id: if &struct virtio_media_resp_header.status == 0, contains the
> + *              id of the newly created session.
> + * @__reserved: must be set to zero by the device.
> + */
> +struct virtio_media_resp_open {
> +       struct virtio_media_resp_header hdr;
> +       u32 session_id;
> +       u32 __reserved;
> +};
> +
> +/**
> + * VIRTIO_MEDIA_CMD_CLOSE - Command for closing an active session.
> + *
> + * This is the equivalent of calling ``close`` on a previously opened V4L2
> + * session. All resources associated with this session will be freed and the
> + * session ID shall not be used again after queueing this command.
> + *
> + * This command does not require a response from the device.
> + */
> +#define VIRTIO_MEDIA_CMD_CLOSE 2
> +
> +/**
> + * struct virtio_media_cmd_close - Driver command for VIRTIO_MEDIA_CMD_CLOSE.
> + * @hdr: header with cmd member set to VIRTIO_MEDIA_CMD_CLOSE.
> + * @session_id: id of the session to close.
> + * @__reserved: must be set to zero by the driver.
> + */
> +struct virtio_media_cmd_close {
> +       struct virtio_media_cmd_header hdr;
> +       u32 session_id;
> +       u32 __reserved;
> +};
> +
> +/**
> + * VIRTIO_MEDIA_CMD_IOCTL - Driver command for executing an ioctl.
> + *
> + * This command asks the device to run one of the ``VIDIOC_*`` ioctls on the
> + * active session.
> + *
> + * The code of the ioctl is extracted from the VIDIOC_* definitions in
> + * ``videodev2.h``, and consists of the second argument of the ``_IO*`` macro.
> + *
> + * Each ioctl has a payload, which is defined by the third argument of the
> + * ``_IO*`` macro defining it. It can be writable by the driver (``_IOW``), the
> + * device (``_IOR``), or both (``_IOWR``).
> + *
> + * If an ioctl is writable by the driver, it must be followed by a
> + * driver-writable descriptor containing the payload.
> + *
> + * If an ioctl is writable by the device, it must be followed by a
> + * device-writable descriptor of the size of the payload that the device will
> + * write into.
> + *
> + */
> +#define VIRTIO_MEDIA_CMD_IOCTL 3
> +
> +/**
> + * struct virtio_media_cmd_ioctl - Driver command for VIRTIO_MEDIA_CMD_IOCTL.
> + * @hdr: header with cmd member set to VIRTIO_MEDIA_CMD_IOCTL.
> + * @session_id: id of the session to run the ioctl on.
> + * @code: code of the ioctl to run.
> + */
> +struct virtio_media_cmd_ioctl {
> +       struct virtio_media_cmd_header hdr;
> +       u32 session_id;
> +       u32 code;
> +};
> +
> +/**
> + * struct virtio_media_resp_ioctl - Device response for VIRTIO_MEDIA_CMD_IOCTL.
> + * @hdr: header containing the status of the ioctl.
> + */
> +struct virtio_media_resp_ioctl {
> +       struct virtio_media_resp_header hdr;
> +};
> +
> +/**
> + * struct virtio_media_sg_entry - Description of part of a scattered guest
> + *                                memory.
> + * @start: start guest address of the memory segment.
> + * @len: length of this memory segment.
> + * @__reserved: must be set to zero by the driver.
> + */
> +struct virtio_media_sg_entry {
> +       u64 start;
> +       u32 len;
> +       u32 __reserved;
> +};
> +
> +/**
> + * VIRTIO_MEDIA_MMAP_FLAG_RW - Bit position of the VIRTIO_MEDIA_MMAP_FLAG_RW
> + *                             flag.
> + */
> +#define VIRTIO_MEDIA_MMAP_FLAG_RW 0
> +
> +/**
> + * VIRTIO_MEDIA_CMD_MMAP - Command for mapping a MMAP buffer into the driver's
> + *                         address space.
> + */
> +#define VIRTIO_MEDIA_CMD_MMAP 4
> +
> +/**
> + * struct virtio_media_cmd_mmap - Driver command for VIRTIO_MEDIA_CMD_MMAP.
> + * @hdr: header with cmd member set to VIRTIO_MEDIA_CMD_MMAP.
> + * @session_id: ID of the session we are mapping for.
> + * @flags: combination of VIRTIO_MEDIA_MMAP_FLAG_*.
> + * @offset: mem_offset field of the plane to map, as returned by
> + *          VIDIOC_QUERYBUF.
> + */
> +struct virtio_media_cmd_mmap {
> +       struct virtio_media_cmd_header hdr;
> +       u32 session_id;
> +       u32 flags;
> +       u32 offset;
> +};
> +
> +/**
> + * struct virtio_media_resp_mmap - Device response for VIRTIO_MEDIA_CMD_MMAP.
> + * @hdr: header containing the status of the command.
> + * @driver_addr: offset into SHM region 0 of the start of the mapping.
> + * @len: length of the mapping.
> + */
> +struct virtio_media_resp_mmap {
> +       struct virtio_media_resp_header hdr;
> +       u64 driver_addr;
> +       u64 len;
> +};
> +
> +/**
> + * VIRTIO_MEDIA_CMD_MUNMAP - Unmap a MMAP buffer previously mapped using
> + *                           VIRTIO_MEDIA_CMD_MMAP.
> + */
> +#define VIRTIO_MEDIA_CMD_MUNMAP 5
> +
> +/**
> + * struct virtio_media_cmd_munmap - Driver command for VIRTIO_MEDIA_CMD_MUNMAP.
> + * @hdr: header with cmd member set to VIRTIO_MEDIA_CMD_MUNMAP.
> + * @driver_addr: offset into SHM region 0 at which the buffer has been
> + *               previously mapped.
> + */
> +struct virtio_media_cmd_munmap {
> +       struct virtio_media_cmd_header hdr;
> +       u64 driver_addr;
> +};
> +
> +/**
> + * struct virtio_media_resp_munmap - Device response for
> + *                                   VIRTIO_MEDIA_CMD_MUNMAP.
> + * @hdr: header containing the status of the command.
> + */
> +struct virtio_media_resp_munmap {
> +       struct virtio_media_resp_header hdr;
> +};
> +
> +/* The values for these events are set by the virtio-media specification. */
> +#define VIRTIO_MEDIA_EVT_ERROR 0
> +#define VIRTIO_MEDIA_EVT_DQBUF 1
> +#define VIRTIO_MEDIA_EVT_EVENT 2
> +
> +/**
> + * struct virtio_media_event_header - Header for events on the eventq.
> + * @event: one of VIRTIO_MEDIA_EVT_*
> + * @session_id: ID of the session the event applies to.
> + */
> +struct virtio_media_event_header {
> +       u32 event;
> +       u32 session_id;
> +};
> +
> +/**
> + * struct virtio_media_event_error - Unrecoverable device-side error.
> + * @hdr: header for the event.
> + * @errno: error code describing the kind of error that occurred.
> + * @__reserved: must be set to zero by the device.
> + *
> + * Upon receiving this event, the session mentioned in the header is considered
> + * corrupted and closed.
> + */
> +struct virtio_media_event_error {
> +       struct virtio_media_event_header hdr;
> +       u32 errno;
> +       u32 __reserved;
> +};
> +
> +/* This is set to VIDEO_MAX_PLANES defined in include/uapi/linux/videodev2.h.
> + * It is renamed here to match the constant that is defined in the virtio-media
> + * specification.
> + */
> +#define VIRTIO_MEDIA_MAX_PLANES VIDEO_MAX_PLANES
> +
> +/**
> + * struct virtio_media_event_dqbuf - Dequeued buffer event.
> + * @hdr: header for the event.
> + * @buffer: &struct v4l2_buffer describing the buffer that has been dequeued.
> + * @planes: plane information for the dequeued buffer.
> + *
> + * This event is used to signal that a buffer is not being used anymore by the
> + * device and is returned to the driver.
> + */
> +struct virtio_media_event_dqbuf {
> +       struct virtio_media_event_header hdr;
> +       struct v4l2_buffer buffer;
> +       struct v4l2_plane planes[VIRTIO_MEDIA_MAX_PLANES];
> +};
> +
> +/**
> + * struct virtio_media_event_event - V4L2 event.
> + * @hdr: header for the event.
> + * @event: description of the event that occurred.
> + *
> + * This event signals that a V4L2 event has been emitted for a session.
> + */
> +struct virtio_media_event_event {
> +       struct virtio_media_event_header hdr;
> +       struct v4l2_event event;
> +};
> +
> +/* Maximum size of an event. We will queue descriptors of this size on the
> + * eventq.
> + */
> +#define VIRTIO_MEDIA_EVENT_MAX_SIZE sizeof(struct virtio_media_event_dqbuf)
> +
> +#endif // __VIRTIO_MEDIA_PROTOCOL_H
> --
> 2.55.0.737.g08866a6d13-goog
>