1.. Permission is granted to copy, distribute and/or modify this 2.. document under the terms of the GNU Free Documentation License, 3.. Version 1.1 or any later version published by the Free Software 4.. Foundation, with no Invariant Sections, no Front-Cover Texts 5.. and no Back-Cover Texts. A copy of the license is included at 6.. Documentation/userspace-api/media/fdl-appendix.rst. 7.. 8.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections 9 10.. _func-open: 11 12*********** 13V4L2 open() 14*********** 15 16Name 17==== 18 19v4l2-open - Open a V4L2 device 20 21 22Synopsis 23======== 24 25.. code-block:: c 26 27 #include <fcntl.h> 28 29 30.. c:function:: int open( const char *device_name, int flags ) 31 :name: v4l2-open 32 33Arguments 34========= 35 36``device_name`` 37 Device to be opened. 38 39``flags`` 40 Open flags. Access mode must be ``O_RDWR``. This is just a 41 technicality, input devices still support only reading and output 42 devices only writing. 43 44 When the ``O_NONBLOCK`` flag is given, the :ref:`read() <func-read>` 45 function and the :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl will 46 return the ``EAGAIN`` error code when no data is available or no 47 buffer is in the driver outgoing queue, otherwise these functions 48 block until data becomes available. All V4L2 drivers exchanging data 49 with applications must support the ``O_NONBLOCK`` flag. 50 51 Other flags have no effect. 52 53 54Description 55=========== 56 57To open a V4L2 device applications call :ref:`open() <func-open>` with the 58desired device name. This function has no side effects; all data format 59parameters, current input or output, control values or other properties 60remain unchanged. At the first :ref:`open() <func-open>` call after loading the 61driver they will be reset to default values, drivers are never in an 62undefined state. 63 64 65Return Value 66============ 67 68On success :ref:`open() <func-open>` returns the new file descriptor. On error 69-1 is returned, and the ``errno`` variable is set appropriately. 70Possible error codes are: 71 72EACCES 73 The caller has no permission to access the device. 74 75EBUSY 76 The driver does not support multiple opens and the device is already 77 in use. 78 79ENXIO 80 No device corresponding to this device special file exists. 81 82ENOMEM 83 Not enough kernel memory was available to complete the request. 84 85EMFILE 86 The process already has the maximum number of files open. 87 88ENFILE 89 The limit on the total number of files open on the system has been 90 reached. 91