vb2_prepare_buf(9)

💅 vb2_prepare_buf(9) — Kernel API Manual edition 💅

🎀 NAME 🎀

vb2_prepare_buf — Pass ownership of a buffer from userspace to the kernel. That's the whole serve: userspace hands the buffer over, kernel takes the wheel. 👑

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✨ SYNOPSIS ✨

okay bestie, the call looks exactly like this, no cap:

int vb2_prepare_buf (struct vb2_queue *q , struct media_device *mdev ,
       struct v4l2_buffer *b );

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🫶 ARGUMENTS 🫶

• q — pointer to struct vb2_queue with videobuf2 queue. This is the videobuf2 queue situation, iconic.
• mdev — pointer to struct media_device, may be NULL. Not a typo, bestie, NULL is allowed here. 🙈
• b — buffer structure passed from userspace to v4l2_ioctl_ops->vidioc_prepare_buf handler in driver.

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🔥 DESCRIPTION 🔥

Should be called from the v4l2_ioctl_ops->vidioc_prepare_buf ioctl handler of a driver. Like, that's its whole main-character entrance. ✨

This function:

1. verifies the passed buffer.
2. calls vb2_ops->buf_prepare callback in the driver (if provided), in which driver-specific buffer initialization can be performed.
3. if b->request_fd is non-zero and mdev->ops->req_queue is set, then bind the prepared buffer to the request.

The return values from this function are intended to be directly returned from v4l2_ioctl_ops->vidioc_prepare_buf handler in driver. So don't get creative with them — hand them straight back. 💅

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🌈 SEE ALSO 🌈

go read these too, they're all part of the lore:

• Kernel file ./include/media/videobuf2-v4l2.h struct vb2_v4l2_buffer(9)
• vb2_find_buffer(9)
• vb2_querybuf(9)
• vb2_reqbufs(9)
• vb2_create_bufs(9)
• vb2_qbuf(9)
• vb2_expbuf(9)
• vb2_dqbuf(9)
• vb2_streamon(9)
• vb2_streamoff(9)
• vb2_queue_init(9)
• vb2_queue_init_name(9)
• vb2_queue_release(9)
• vb2_queue_change_type(9)
• vb2_poll(9)
• vb2_queue_is_busy(9)
• vb2_video_unregister_device(9)

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mwah 💋 — source/version ./include/media, date October 2026, page vb2_prepare_buf(9). bye bestie, go prepare those buffers 🫶