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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/rc/lirc-read.rst | |
parent | Initial commit. (diff) | |
download | linux-upstream/5.10.209.tar.xz linux-upstream/5.10.209.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | Documentation/userspace-api/media/rc/lirc-read.rst | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/rc/lirc-read.rst b/Documentation/userspace-api/media/rc/lirc-read.rst new file mode 100644 index 000000000..d58956021 --- /dev/null +++ b/Documentation/userspace-api/media/rc/lirc-read.rst @@ -0,0 +1,65 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: RC + +.. _lirc-read: + +*********** +LIRC read() +*********** + +Name +==== + +lirc-read - Read from a LIRC device + +Synopsis +======== + +.. code-block:: c + + #include <unistd.h> + +.. c:function:: ssize_t read( int fd, void *buf, size_t count ) + +Arguments +========= + +``fd`` + File descriptor returned by ``open()``. + +``buf`` + Buffer to be filled + +``count`` + Max number of bytes to read + +Description +=========== + +:c:func:`read()` attempts to read up to ``count`` bytes from file +descriptor ``fd`` into the buffer starting at ``buf``. If ``count`` is zero, +:c:func:`read()` returns zero and has no other results. If ``count`` +is greater than ``SSIZE_MAX``, the result is unspecified. + +The exact format of the data depends on what :ref:`lirc_modes` a driver +uses. Use :ref:`lirc_get_features` to get the supported mode, and use +:ref:`lirc_set_rec_mode` set the current active mode. + +The mode :ref:`LIRC_MODE_MODE2 <lirc-mode-mode2>` is for raw IR, +in which packets containing an unsigned int value describing an IR signal are +read from the chardev. + +Alternatively, :ref:`LIRC_MODE_SCANCODE <lirc-mode-scancode>` can be available, +in this mode scancodes which are either decoded by software decoders, or +by hardware decoders. The :c:type:`rc_proto` member is set to the +:ref:`IR protocol <Remote_controllers_Protocols>` +used for transmission, and ``scancode`` to the decoded scancode, +and the ``keycode`` set to the keycode or ``KEY_RESERVED``. + +Return Value +============ + +On success, the number of bytes read is returned. It is not an error if +this number is smaller than the number of bytes requested, or the amount +of data required for one frame. On error, -1 is returned, and the ``errno`` +variable is set appropriately. |