STRUCT V4L2_PLANE(9)

💅 struct v4l2_plane — plane info for multi-planar buffers

okay bestie, welcome to the Kernel API Manual ✨ this one's short but it's important, so pay attention 🫶 It's literally the struct that holds the deets for one single plane inside a multi-planar buffer. no cap.

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🌸 SYNOPSIS 🌸

struct v4l2_plane {
    __u32 bytesused;
    __u32 length;
    union {
      __u32 mem_offset;
      unsigned long   userptr;
      __s32 fd;
    } m;
    __u32 data_offset;
    __u32 reserved[11];
 };

like… look at her. she's gorgeous. 💖

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🎀 Members 🎀

• bytesused — the number of bytes that data actually occupies in the plane, aka the payload. the real content. the main character energy 🫶
• length — the size of this plane itself, in bytes. and bestie, read this twice: it is NOT the payload. it's the container, not the snack. 💀
• m — the union of mem_offset, userptr and fd. she contains multitudes 💅
• m.mem_offset — when the memory in the associated struct v4l2_buffer is V4L2_MEMORY_MMAP, this equals the offset from the start of the device memory for this plane — or it's a "cookie" that should be passed to mmap called on the video node 🍪 lowkey iconic
• m.userptr — when the memory is V4L2_MEMORY_USERPTR, this is a userspace pointer pointing right at this plane 🔥
• m.fd — when the memory is V4L2_MEMORY_DMABUF, this is a userspace file descriptor associated with this plane 🦋
• data_offset — offset in the plane to the start of the data. usually 0, unless there's a header sitting in front of the data 🙈 (there's always someone in front of you in line, fr fr)
• reserved — drivers and applications must zero this array. not "should", not "maybe", must. zero it out bestie 😭

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✨ Description ✨

so multi-planar buffers are made of one or more planes, right? 🌈 like, an YCbCr buffer with two planes can have one plane for Y, and another for the interleaved CbCr components. that's the vibe 💜

Each plane can live in a separate memory buffer — or even in a completely separate memory node (e.g. in embedded devices 👑). literally independent. they don't even have to be in the same neighborhood. slay.

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🔥 SEE ALSO 🔥

Kernel file ./include/uapi/linux/videodev2.h — go read the source, iykyk 📖 and also go say hi to her friends:

• struct v4l2_capability(9)
• struct v4l2_buffer(9)
• v4l2_timeval_to_ns(9)
• struct v4l2_exportbuffer(9)
• struct v4l2_selection(9)
• struct v4l2_plane_pix_format(9)
• struct v4l2_pix_format_mplane(9)
• struct v4l2_sdr_format(9)
• struct v4l2_meta_format(9)
• struct v4l2_format(9)
• struct v4l2_event_motion_det(9)
• struct v4l2_create_buffers(9)
• struct v4l2_remove_buffers(9)

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and that's the whole page, bestie 💫 this one lives in ./include/uapi/linux, dated October 2026, and it's filed under struct v4l2_plane(9) — go forth and zero your reserved array 🎀💖✨