7.52. ioctl VIDIOC_EXT_QUERYBUF¶
VIDIOC_EXT_QUERYBUF - Query the status of a buffer
Applications set the
type field of a struct
v4l2_ext_buffer to the same buffer type as was
previously used with struct
index field. Valid index numbers range from zero to the
number of buffers allocated with
ioctl VIDIOC_EXT_CREATE_BUFS (struct
reserved field must be set to 0.
flags field the
V4L2_BUF_FLAG_DONE flags will be valid. The
planes.memory fields will be
set to the current I/O method for each plane.
For every valid plane, an entry in
planes will be filled, and zeroed for
planes[i].buffer_length is the size of the memory buffer
which contains the plane,
planes[i].plane_length is the length of the plane,
and ``planes[i].offset` is where the plane is placed in the memory buffer.
The size of the
planes array can be calculated by the number of sequential
planes[i].buffer_length that differs from zero up to the max
size of the array.