STRUCT V4L2_BUFFER(9)

struct v4l2_buffer(9) 💅

okay bestie, welcome to the Kernel API Manual page for struct v4l2_buffer — literally the video buffer info struct, and yes it's giving very "main character data exchange" energy ✨

NAME 🎀

struct v4l2_buffer — video buffer info

SYNOPSIS 🦋

struct v4l2_buffer {
    __u32 index;
    __u32 type;
    __u32 bytesused;
    __u32 flags;
    __u32 field;
  #ifdef __KERNEL__;
    struct __kernel_v4l2_timeval timestamp;
  #else;
    struct timeval          timestamp;
  #endif;
    struct v4l2_timecode    timecode;
    __u32 sequence;
    __u32 memory;
    union {
      __u32 offset;
      unsigned long   userptr;
      struct v4l2_plane *planes;
      __s32 fd;
    } m;
    __u32 length;
    __u32 reserved2;
    union {
      __s32 request_fd;
      __u32 reserved;
    };
 };

Members 💖

index — id number of the buffer
type — enum v4l2_buf_type; buffer type (type == *_MPLANE for multiplanar buffers)
bytesused — number of bytes occupied by data in the buffer (payload); unused (set to 0) for multiplanar buffers
flags — buffer informational flags
field — enum v4l2_field; field order of the image in the buffer
timestamp — frame timestamp
timestamp — frame timestamp (yes bestie, it really is listed twice on this page — we're keeping both, no cap)
timecode — frame timecode
sequence — sequence count of this frame
memory — enum v4l2_memory; the method, in which the actual video data is passed
m — union of offset, userptr, planes and fd
m.offset — for non-multiplanar buffers with memory == V4L2_MEMORY_MMAP; offset from the start of the device memory for this plane, (or a "cookie" that should be passed to mmap as offset)
m.userptr — for non-multiplanar buffers with memory == V4L2_MEMORY_USERPTR; a userspace pointer pointing to this buffer
m.planes — for multiplanar buffers; userspace pointer to the array of plane info structs for this buffer
m.fd — for non-multiplanar buffers with memory == V4L2_MEMORY_DMABUF; a userspace file descriptor associated with this buffer
length — size in bytes of the buffer (NOT its payload) for single-plane buffers (when type != *_MPLANE); number of elements in the planes array for multi-plane buffers
reserved2 — drivers and applications must zero this field
{unnamed_union} — anonymous
request_fd — fd of the request that this buffer should use
reserved — for backwards compatibility with applications that do not know about request_fd

Description 🌸

Contains data exchanged by application and driver using one of the Streaming I/O methods. That's the whole vibe: this struct is the little messenger carrying buffer info back and forth 💌