vb2_qbuf(9)

💅 vb2_qbuf — like, the kernel API manual page, bestie

okay so real quick: this is vb2_qbuf(9), straight out of the Kernel API Manual, and it's the function that queues a buffer from userspace. yes. that one. let's get into it 🎀

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✨ SYNOPSIS ✨

int vb2_qbuf (struct vb2_queue *q , struct media_device *mdev , struct v4l2_buffer *b );

three args, one int back, no cap. 🫶

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🌸 ARGUMENTS 🌸

• q — pointer to struct vb2_queue with the videobuf2 queue. that's your queue, she's the main character here 👑
• mdev — pointer to struct media_device, and heads up: it may be NULL. so don't panic if it's giving "nothing" 💀
• b — the buffer structure passed from userspace to the v4l2_ioctl_ops->vidioc_qbuf handler in the driver. this is the actual buffer the user is handing you, bestie 🙈

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🔥 DESCRIPTION 🔥

Should be called from v4l2_ioctl_ops->vidioc_qbuf handler of a driver. literally that's its whole job, it's giving very "I have one purpose and I ate" 💅

So here's what this function does, step by step:

1. verifies the passed buffer ✨
2. if b->request_fd is non-zero and mdev->ops->req_queue is set, then bind the buffer to the request
3. if necessary, calls the vb2_ops->buf_prepare callback in the driver (if provided), in which driver-specific buffer initialization can be performed
4. if streaming is on, queues the buffer in the driver by the means of the vb2_ops->buf_queue callback for processing

The return values from this function are intended to be directly returned from the v4l2_ioctl_ops->vidioc_qbuf handler in the driver. so like — don't overthink it, just pass that int straight on through 🧚

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👑 SEE ALSO 👑

Kernel file ./include/media/videobuf2-v4l2.h and honestly the whole friend group:

• struct vb2_v4l2_buffer(9)
• vb2_find_buffer(9)
• vb2_querybuf(9)
• vb2_reqbufs(9)
• vb2_create_bufs(9)
• vb2_prepare_buf(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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ok that's the whole page, go queue your buffers, ily, bye 💖

mwah 💋 — this little number lives in ./include/media, dated October 2026, and it's vb2_qbuf(9) forever and always. slay. periodt. 🌈