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Based on kernel version 4.16.1. Page generated on 2018-04-09 11:52 EST.

1	Linux Braille Console
2	=====================
3	
4	To get early boot messages on a braille device (before userspace screen
5	readers can start), you first need to compile the support for the usual serial
6	console (see :ref:`Documentation/admin-guide/serial-console.rst <serial_console>`), and
7	for braille device
8	(in :menuselection:`Device Drivers --> Accessibility support --> Console on braille device`).
9	
10	Then you need to specify a ``console=brl``, option on the kernel command line, the
11	format is::
12	
13		console=brl,serial_options...
14	
15	where ``serial_options...`` are the same as described in
16	:ref:`Documentation/admin-guide/serial-console.rst <serial_console>`.
17	
18	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
19	override the baud rate to 115200, etc.
20	
21	By default, the braille device will just show the last kernel message (console
22	mode).  To review previous messages, press the Insert key to switch to the VT
23	review mode.  In review mode, the arrow keys permit to browse in the VT content,
24	:kbd:`PAGE-UP`/:kbd:`PAGE-DOWN` keys go at the top/bottom of the screen, and
25	the :kbd:`HOME` key goes back
26	to the cursor, hence providing very basic screen reviewing facility.
27	
28	Sound feedback can be obtained by adding the ``braille_console.sound=1`` kernel
29	parameter.
30	
31	For simplicity, only one braille console can be enabled, other uses of
32	``console=brl,...`` will be discarded.  Also note that it does not interfere with
33	the console selection mechanism described in
34	:ref:`Documentation/admin-guide/serial-console.rst <serial_console>`.
35	
36	For now, only the VisioBraille device is supported.
37	
38	Samuel Thibault <samuel.thibault@ens-lyon.org>
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