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38 lines
1.7 KiB
38 lines
1.7 KiB
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 <[email protected]>
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