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authorMauro Carvalho Chehab <mchehab@s-opensource.com>2016-09-21 14:51:11 +0200
committerMauro Carvalho Chehab <mchehab@s-opensource.com>2016-10-24 12:12:35 +0200
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tree4629e2dedf4a9ed45a6855c129101f9b52138372 /Documentation/admin-guide/braille-console.rst
parentdocs-rst: add documents to development-process (diff)
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docs-rst: create an user's manual book
Place README, REPORTING-BUGS, SecurityBugs and kernel-parameters on an user's manual book. As we'll be numbering the user's manual, remove the manual numbering from SecurityBugs. Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
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+Linux Braille Console
+=====================
+
+To get early boot messages on a braille device (before userspace screen
+readers can start), you first need to compile the support for the usual serial
+console (see :ref:`Documentation/serial-console.txt <serial_console>`), and
+for braille device
+(in :menuselection:`Device Drivers --> Accessibility support --> Console on braille device`).
+
+Then you need to specify a ``console=brl``, option on the kernel command line, the
+format is::
+
+ console=brl,serial_options...
+
+where ``serial_options...`` are the same as described in
+:ref:`Documentation/serial-console.txt <serial_console>`.
+
+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
+override the baud rate to 115200, etc.
+
+By default, the braille device will just show the last kernel message (console
+mode). To review previous messages, press the Insert key to switch to the VT
+review mode. In review mode, the arrow keys permit to browse in the VT content,
+:kbd:`PAGE-UP`/:kbd:`PAGE-DOWN` keys go at the top/bottom of the screen, and
+the :kbd:`HOME` key goes back
+to the cursor, hence providing very basic screen reviewing facility.
+
+Sound feedback can be obtained by adding the ``braille_console.sound=1`` kernel
+parameter.
+
+For simplicity, only one braille console can be enabled, other uses of
+``console=brl,...`` will be discarded. Also note that it does not interfere with
+the console selection mechanism described in
+:ref:`Documentation/serial-console.txt <serial_console>`.
+
+For now, only the VisioBraille device is supported.
+
+Samuel Thibault <samuel.thibault@ens-lyon.org>