1*4882a593Smuzhiyun.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2*4882a593Smuzhiyun.. c:namespace:: DTV.dmx 3*4882a593Smuzhiyun 4*4882a593Smuzhiyun.. _DMX_QUERYBUF: 5*4882a593Smuzhiyun 6*4882a593Smuzhiyun****************** 7*4882a593Smuzhiyunioctl DMX_QUERYBUF 8*4882a593Smuzhiyun****************** 9*4882a593Smuzhiyun 10*4882a593SmuzhiyunName 11*4882a593Smuzhiyun==== 12*4882a593Smuzhiyun 13*4882a593SmuzhiyunDMX_QUERYBUF - Query the status of a buffer 14*4882a593Smuzhiyun 15*4882a593Smuzhiyun.. warning:: this API is still experimental 16*4882a593Smuzhiyun 17*4882a593SmuzhiyunSynopsis 18*4882a593Smuzhiyun======== 19*4882a593Smuzhiyun 20*4882a593Smuzhiyun.. c:macro:: DMX_QUERYBUF 21*4882a593Smuzhiyun 22*4882a593Smuzhiyun``int ioctl(int fd, DMX_QUERYBUF, struct dvb_buffer *argp)`` 23*4882a593Smuzhiyun 24*4882a593SmuzhiyunArguments 25*4882a593Smuzhiyun========= 26*4882a593Smuzhiyun 27*4882a593Smuzhiyun``fd`` 28*4882a593Smuzhiyun File descriptor returned by :c:func:`open()`. 29*4882a593Smuzhiyun 30*4882a593Smuzhiyun``argp`` 31*4882a593Smuzhiyun Pointer to struct :c:type:`dvb_buffer`. 32*4882a593Smuzhiyun 33*4882a593SmuzhiyunDescription 34*4882a593Smuzhiyun=========== 35*4882a593Smuzhiyun 36*4882a593SmuzhiyunThis ioctl is part of the mmap streaming I/O method. It can 37*4882a593Smuzhiyunbe used to query the status of a buffer at any time after buffers have 38*4882a593Smuzhiyunbeen allocated with the :ref:`DMX_REQBUFS` ioctl. 39*4882a593Smuzhiyun 40*4882a593SmuzhiyunApplications set the ``index`` field. Valid index numbers range from zero 41*4882a593Smuzhiyunto the number of buffers allocated with :ref:`DMX_REQBUFS` 42*4882a593Smuzhiyun(struct :c:type:`dvb_requestbuffers` ``count``) minus one. 43*4882a593Smuzhiyun 44*4882a593SmuzhiyunAfter calling :ref:`DMX_QUERYBUF` with a pointer to this structure, 45*4882a593Smuzhiyundrivers return an error code or fill the rest of the structure. 46*4882a593Smuzhiyun 47*4882a593SmuzhiyunOn success, the ``offset`` will contain the offset of the buffer from the 48*4882a593Smuzhiyunstart of the device memory, the ``length`` field its size, and the 49*4882a593Smuzhiyun``bytesused`` the number of bytes occupied by data in the buffer (payload). 50*4882a593Smuzhiyun 51*4882a593SmuzhiyunReturn Value 52*4882a593Smuzhiyun============ 53*4882a593Smuzhiyun 54*4882a593SmuzhiyunOn success 0 is returned, the ``offset`` will contain the offset of the 55*4882a593Smuzhiyunbuffer from the start of the device memory, the ``length`` field its size, 56*4882a593Smuzhiyunand the ``bytesused`` the number of bytes occupied by data in the buffer 57*4882a593Smuzhiyun(payload). 58*4882a593Smuzhiyun 59*4882a593SmuzhiyunOn error it returns -1 and the ``errno`` variable is set 60*4882a593Smuzhiyunappropriately. The generic error codes are described at the 61*4882a593Smuzhiyun:ref:`Generic Error Codes <gen-errors>` chapter. 62*4882a593Smuzhiyun 63*4882a593SmuzhiyunEINVAL 64*4882a593Smuzhiyun The ``index`` is out of bounds. 65