3.2.17. ioctl DMX_QUERYBUF¶
3.2.17.1. Name¶
DMX_QUERYBUF - Query the status of a buffer
Warning
this API is still experimental
3.2.17.2. Synopsis¶
-
DMX_QUERYBUF¶
int ioctl(int fd, DMX_QUERYBUF, struct dvb_buffer *argp)
3.2.17.3. Arguments¶
fdFile descriptor returned by
open().argpPointer to struct
dvb_buffer.
3.2.17.4. Description¶
This ioctl is part of the mmap streaming I/O method. It can be used to query the status of a buffer at any time after buffers have been allocated with the ioctl DMX_REQBUFS ioctl.
Applications set the index field. Valid index numbers range from zero
to the number of buffers allocated with ioctl DMX_REQBUFS
(struct dvb_requestbuffers count) minus one.
After calling ioctl DMX_QUERYBUF with a pointer to this structure, drivers return an error code or fill the rest of the structure.
On success, the offset will contain the offset of the buffer from the
start of the device memory, the length field its size, and the
bytesused the number of bytes occupied by data in the buffer (payload).
3.2.17.5. Return Value¶
On success 0 is returned, the offset will contain the offset of the
buffer from the start of the device memory, the length field its size,
and the bytesused the number of bytes occupied by data in the buffer
(payload).
On error it returns -1 and the errno variable is set
appropriately. The generic error codes are described at the
Generic Error Codes chapter.
- EINVAL
The
indexis out of bounds.