.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later .. c:namespace:: DTV.dmx

.. _DMX_QUERYBUF:

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ioctl DMX_QUERYBUF

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Name

DMX_QUERYBUF - Query the status of a buffer

.. warning:: this API is still experimental

Synopsis

.. c:macro:: DMX_QUERYBUF

int ioctl(int fd, DMX_QUERYBUF, struct dvb_buffer *argp)

Arguments

fd File descriptor returned by :c:func:open().

argp Pointer to struct :c:type:dvb_buffer.

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 :ref:DMX_REQBUFS ioctl.

Applications set the index field. Valid index numbers range from zero to the number of buffers allocated with :ref:DMX_REQBUFS (struct :c:type:dvb_requestbuffers count) minus one.

After calling :ref: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).

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 :ref:Generic Error Codes <gen-errors> chapter.

EINVAL The index is out of bounds.