39 lines
1.7 KiB
ReStructuredText
39 lines
1.7 KiB
ReStructuredText
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Linux Braille Console
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=====================
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To get early boot messages on a braille device (before userspace screen
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readers can start), you first need to compile the support for the usual serial
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console (see :ref:`Documentation/admin-guide/serial-console.rst <serial_console>`), and
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for braille device
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(in :menuselection:`Device Drivers --> Accessibility support --> Console on braille device`).
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Then you need to specify a ``console=brl``, option on the kernel command line, the
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format is::
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console=brl,serial_options...
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where ``serial_options...`` are the same as described in
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:ref:`Documentation/admin-guide/serial-console.rst <serial_console>`.
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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
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override the baud rate to 115200, etc.
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By default, the braille device will just show the last kernel message (console
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mode). To review previous messages, press the Insert key to switch to the VT
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review mode. In review mode, the arrow keys permit to browse in the VT content,
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:kbd:`PAGE-UP`/:kbd:`PAGE-DOWN` keys go at the top/bottom of the screen, and
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the :kbd:`HOME` key goes back
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to the cursor, hence providing very basic screen reviewing facility.
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Sound feedback can be obtained by adding the ``braille_console.sound=1`` kernel
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parameter.
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For simplicity, only one braille console can be enabled, other uses of
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``console=brl,...`` will be discarded. Also note that it does not interfere with
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the console selection mechanism described in
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:ref:`Documentation/admin-guide/serial-console.rst <serial_console>`.
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For now, only the VisioBraille device is supported.
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Samuel Thibault <samuel.thibault@ens-lyon.org>
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