Orange Pi5 kernel

^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  1) .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  2) .. c:namespace:: DTV.dmx
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  3) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  4) .. _DMX_REQBUFS:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  5) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  6) *****************
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  7) ioctl DMX_REQBUFS
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  8) *****************
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  9) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) Name
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) ====
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) DMX_REQBUFS - Initiate Memory Mapping and/or DMA buffer I/O
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) .. warning:: this API is still experimental
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) Synopsis
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) ========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) .. c:macro:: DMX_REQBUFS
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) ``int ioctl(int fd, DMX_REQBUFS, struct dmx_requestbuffers *argp)``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) Arguments
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) =========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) ``fd``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28)     File descriptor returned by :c:func:`open()`.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) ``argp``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31)     Pointer to struct :c:type:`dmx_requestbuffers`.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) Description
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) ===========
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) This ioctl is used to initiate a memory mapped or DMABUF based demux I/O.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) Memory mapped buffers are located in device memory and must be allocated
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) with this ioctl before they can be mapped into the application's address
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) space. User buffers are allocated by applications themselves, and this
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) ioctl is merely used to switch the driver into user pointer I/O mode and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) to setup some internal structures. Similarly, DMABUF buffers are
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) allocated by applications through a device driver, and this ioctl only
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) configures the driver into DMABUF I/O mode without performing any direct
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) allocation.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) To allocate device buffers applications initialize all fields of the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48) struct :c:type:`dmx_requestbuffers` structure. They set the  ``count`` field
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) to the desired number of buffers,  and ``size`` to the size of each
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50) buffer.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52) When the ioctl is called with a pointer to this structure, the driver will
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53) attempt to allocate the requested number of buffers and it stores the actual
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) number allocated in the ``count`` field. The ``count`` can be smaller than the number requested, even zero, when the driver runs out of free memory. A larger
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55) number is also possible when the driver requires more buffers to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) function correctly. The actual allocated buffer size can is returned
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57) at ``size``, and can be smaller than what's requested.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) When this I/O method is not supported, the ioctl returns an ``EOPNOTSUPP``
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60) error code.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62) Applications can call :ref:`DMX_REQBUFS` again to change the number of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63) buffers, however this cannot succeed when any buffers are still mapped.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) A ``count`` value of zero frees all buffers, after aborting or finishing
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65) any DMA in progress.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67) Return Value
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68) ============
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70) On success 0 is returned, on error -1 and the ``errno`` variable is set
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71) appropriately. The generic error codes are described at the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72) :ref:`Generic Error Codes <gen-errors>` chapter.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74) EOPNOTSUPP
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75)     The  the requested I/O method is not supported.