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Diffstat (limited to 'Documentation/media/uapi/rc/lirc-dev-intro.rst')
| -rw-r--r-- | Documentation/media/uapi/rc/lirc-dev-intro.rst | 75 |
1 files changed, 54 insertions, 21 deletions
diff --git a/Documentation/media/uapi/rc/lirc-dev-intro.rst b/Documentation/media/uapi/rc/lirc-dev-intro.rst index d1936eeb9ce0..3a74fec66d69 100644 --- a/Documentation/media/uapi/rc/lirc-dev-intro.rst +++ b/Documentation/media/uapi/rc/lirc-dev-intro.rst @@ -6,11 +6,12 @@ Introduction ************ -The LIRC device interface is a bi-directional interface for transporting -raw IR data between userspace and kernelspace. Fundamentally, it is just -a chardev (/dev/lircX, for X = 0, 1, 2, ...), with a number of standard -struct file_operations defined on it. With respect to transporting raw -IR data to and fro, the essential fops are read, write and ioctl. +LIRC stands for Linux Infrared Remote Control. The LIRC device interface is +a bi-directional interface for transporting raw IR and decoded scancodes +data between userspace and kernelspace. Fundamentally, it is just a chardev +(/dev/lircX, for X = 0, 1, 2, ...), with a number of standard struct +file_operations defined on it. With respect to transporting raw IR and +decoded scancodes to and fro, the essential fops are read, write and ioctl. Example dmesg output upon a driver registering w/LIRC: @@ -18,7 +19,7 @@ Example dmesg output upon a driver registering w/LIRC: $ dmesg |grep lirc_dev lirc_dev: IR Remote Control driver registered, major 248 - rc rc0: lirc_dev: driver ir-lirc-codec (mceusb) registered at minor = 0 + rc rc0: lirc_dev: driver mceusb registered at minor = 0 What you should see for a chardev: @@ -36,6 +37,43 @@ LIRC modes LIRC supports some modes of receiving and sending IR codes, as shown on the following table. +.. _lirc-mode-scancode: +.. _lirc-scancode-flag-toggle: +.. _lirc-scancode-flag-repeat: + +``LIRC_MODE_SCANCODE`` + + This mode is for both sending and receiving IR. + + For transmitting (aka sending), create a ``struct lirc_scancode`` with + the desired scancode set in the ``scancode`` member, :c:type:`rc_proto` + set the IR protocol, and all other members set to 0. Write this struct to + the lirc device. + + For receiving, you read ``struct lirc_scancode`` from the lirc device, + with ``scancode`` set to the received scancode and the IR protocol + :c:type:`rc_proto`. If the scancode maps to a valid key code, this is set + in the ``keycode`` field, else it is set to ``KEY_RESERVED``. + + The ``flags`` can have ``LIRC_SCANCODE_FLAG_TOGGLE`` set if the toggle + bit is set in protocols that support it (e.g. rc-5 and rc-6), or + ``LIRC_SCANCODE_FLAG_REPEAT`` for when a repeat is received for protocols + that support it (e.g. nec). + + In the Sanyo and NEC protocol, if you hold a button on remote, rather than + repeating the entire scancode, the remote sends a shorter message with + no scancode, which just means button is held, a "repeat". When this is + received, the ``LIRC_SCANCODE_FLAG_REPEAT`` is set and the scancode and + keycode is repeated. + + With nec, there is no way to distinguish "button hold" from "repeatedly + pressing the same button". The rc-5 and rc-6 protocols have a toggle bit. + When a button is released and pressed again, the toggle bit is inverted. + If the toggle bit is set, the ``LIRC_SCANCODE_FLAG_TOGGLE`` is set. + + The ``timestamp`` field is filled with the time nanoseconds + (in ``CLOCK_MONOTONIC``) when the scancode was decoded. + .. _lirc-mode-mode2: ``LIRC_MODE_MODE2`` @@ -72,21 +110,6 @@ on the following table. this packet will be sent, with the number of microseconds with no IR. -.. _lirc-mode-lirccode: - -``LIRC_MODE_LIRCCODE`` - - This mode can be used for IR receive and send. - - The IR signal is decoded internally by the receiver, or encoded by the - transmitter. The LIRC interface represents the scancode as byte string, - which might not be a u32, it can be any length. The value is entirely - driver dependent. This mode is used by some older lirc drivers. - - The length of each code depends on the driver, which can be retrieved - with :ref:`lirc_get_length`. This length is used both - for transmitting and receiving IR. - .. _lirc-mode-pulse: ``LIRC_MODE_PULSE`` @@ -99,3 +122,13 @@ on the following table. of entries. This mode is used only for IR send. + + +************************** +Remote Controller protocol +************************** + +An enum :c:type:`rc_proto` in the :ref:`lirc_header` lists all the +supported IR protocols: + +.. kernel-doc:: include/uapi/linux/lirc.h |