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Basic braille screen reader support

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This adds a minimalistic braille screen reader support.  This is meant to
be used by blind people e.g.  on boot failures or when / cannot be mounted
etc and thus the userland screen readers can not work.

[akpm@linux-foundation.org: fix exports]
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Jiri Kosina <jikos@jikos.cz>
Cc: Dmitry Torokhov <dtor@mail.ru>
Acked-by: Alan Cox <alan@redhat.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Samuel Thibault
2008-04-30 00:54:51 -07:00
committed by Linus Torvalds
parent 730f412c08
commit f7511d5f66
15 changed files with 538 additions and 30 deletions
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34
Documentation/braille-console.txt Normal file
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@@ -0,0 +1,34 @@
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 serial-console.txt), and for braille device (in Device Drivers -
Accessibility).
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 serial-console.txt
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,
page up/down keys go at the top/bottom of the screen, and the 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 mecanism described in serial-console.txt
For now, only the VisioBraille device is supported.
Samuel Thibault <samuel.thibault@ens-lyon.org>

5
Documentation/kernel-parameters.txt
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@@ -496,6 +496,11 @@ and is between 256 and 4096 characters. It is defined in the file
switching to the matching ttyS device later. The
options are the same as for ttyS, above.
If the device connected to the port is not a TTY but a braille
device, prepend "brl," before the device type, for instance
console=brl,ttyS0
For now, only VisioBraille is supported.
earlycon= [KNL] Output early console device and options.
uart[8250],io,<addr>[,options]
uart[8250],mmio,<addr>[,options]