0001 Linux Braille Console
0002 =====================
0003
0004 To get early boot messages on a braille device (before userspace screen
0005 readers can start), you first need to compile the support for the usual serial
0006 console (see :ref:`Documentation/admin-guide/serial-console.rst <serial_console>`), and
0007 for braille device
0008 (in :menuselection:`Device Drivers --> Accessibility support --> Console on braille device`).
0009
0010 Then you need to specify a ``console=brl``, option on the kernel command line, the
0011 format is::
0012
0013 console=brl,serial_options...
0014
0015 where ``serial_options...`` are the same as described in
0016 :ref:`Documentation/admin-guide/serial-console.rst <serial_console>`.
0017
0018 So for instance you can use ``console=brl,ttyS0`` if the braille device is connected to the first serial port, and ``console=brl,ttyS0,115200`` to
0019 override the baud rate to 115200, etc.
0020
0021 By default, the braille device will just show the last kernel message (console
0022 mode). To review previous messages, press the Insert key to switch to the VT
0023 review mode. In review mode, the arrow keys permit to browse in the VT content,
0024 :kbd:`PAGE-UP`/:kbd:`PAGE-DOWN` keys go at the top/bottom of the screen, and
0025 the :kbd:`HOME` key goes back
0026 to the cursor, hence providing very basic screen reviewing facility.
0027
0028 Sound feedback can be obtained by adding the ``braille_console.sound=1`` kernel
0029 parameter.
0030
0031 For simplicity, only one braille console can be enabled, other uses of
0032 ``console=brl,...`` will be discarded. Also note that it does not interfere with
0033 the console selection mechanism described in
0034 :ref:`Documentation/admin-guide/serial-console.rst <serial_console>`.
0035
0036 For now, only the VisioBraille device is supported.
0037
0038 Samuel Thibault <samuel.thibault@ens-lyon.org>
