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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
commit | 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch) | |
tree | a94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/userspace-api/media/dvb/frontend_f_open.rst | |
parent | Initial commit. (diff) | |
download | linux-430c2fc249ea5c0536abd21c23382884005c9093.tar.xz linux-430c2fc249ea5c0536abd21c23382884005c9093.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'Documentation/userspace-api/media/dvb/frontend_f_open.rst')
-rw-r--r-- | Documentation/userspace-api/media/dvb/frontend_f_open.rst | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/dvb/frontend_f_open.rst b/Documentation/userspace-api/media/dvb/frontend_f_open.rst new file mode 100644 index 000000000..bb37eded0 --- /dev/null +++ b/Documentation/userspace-api/media/dvb/frontend_f_open.rst @@ -0,0 +1,104 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: DTV.fe + +.. _frontend_f_open: + +*************************** +Digital TV frontend open() +*************************** + +Name +==== + +fe-open - Open a frontend device + +Synopsis +======== + +.. code-block:: c + + #include <fcntl.h> + +.. c:function:: int open( const char *device_name, int flags ) + +Arguments +========= + +``device_name`` + Device to be opened. + +``flags`` + Open flags. Access can either be ``O_RDWR`` or ``O_RDONLY``. + + Multiple opens are allowed with ``O_RDONLY``. In this mode, only + query and read ioctls are allowed. + + Only one open is allowed in ``O_RDWR``. In this mode, all ioctls are + allowed. + + When the ``O_NONBLOCK`` flag is given, the system calls may return + ``EAGAIN`` error code when no data is available or when the device + driver is temporarily busy. + + Other flags have no effect. + +Description +=========== + +This system call opens a named frontend device +(``/dev/dvb/adapter?/frontend?``) for subsequent use. Usually the first +thing to do after a successful open is to find out the frontend type +with :ref:`FE_GET_INFO`. + +The device can be opened in read-only mode, which only allows monitoring +of device status and statistics, or read/write mode, which allows any +kind of use (e.g. performing tuning operations.) + +In a system with multiple front-ends, it is usually the case that +multiple devices cannot be open in read/write mode simultaneously. As +long as a front-end device is opened in read/write mode, other open() +calls in read/write mode will either fail or block, depending on whether +non-blocking or blocking mode was specified. A front-end device opened +in blocking mode can later be put into non-blocking mode (and vice +versa) using the F_SETFL command of the fcntl system call. This is a +standard system call, documented in the Linux manual page for fcntl. +When an open() call has succeeded, the device will be ready for use in +the specified mode. This implies that the corresponding hardware is +powered up, and that other front-ends may have been powered down to make +that possible. + +Return Value +============ + +On success :c:func:`open()` returns the new file descriptor. +On error, -1 is returned, and the ``errno`` variable is set appropriately. + +Possible error codes are: + +On success 0 is returned, and :c:type:`ca_slot_info` is filled. + +On error -1 is returned, and the ``errno`` variable is set +appropriately. + +.. tabularcolumns:: |p{2.5cm}|p{15.0cm}| + +.. flat-table:: + :header-rows: 0 + :stub-columns: 0 + :widths: 1 16 + + - - ``EPERM`` + - The caller has no permission to access the device. + + - - ``EBUSY`` + - The the device driver is already in use. + + - - ``EMFILE`` + - The process already has the maximum number of files open. + + - - ``ENFILE`` + - The limit on the total number of files open on the system has been + reached. + +The generic error codes are described at the +:ref:`Generic Error Codes <gen-errors>` chapter. |