#2722: Mistake on the linux console page
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Reporter: splotz90 | Owner: lfs-b...@…
Type: task | Status: new
Priority: normal | Milestone: 6.7
Component: Book | Version: SVN
Severity: normal | Keywords:
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The book says:
"'''''In UTF-8 mode, the kernel uses the application character map for
conversion of composed 8-bit key codes in the keymap to UTF-8, and thus
the argument of the "-m" parameter should be set to the encoding of the
composed key codes in the keymap.'''''"
That's wrong. The man page of setfont says:
"'''''If the console is in utf8 mode (see unicode_start(1)) then the
kernel expects that user program output is coded as UTF-8 (see utf-8(7)),
and converts that to Unicode (ucs2). Otherwise, a translation table is
used from the 8-bit program output to 16-bit Unicode values. Such a
translation table is called a Unicode console map.'''''"
The console internal always uses unicode (regardless if we're using the
unicode mode or not):
http://www.mjmwired.net/kernel/Documentation/unicode.txt
So this table is used to convert the output of programs, that are using
"legacy charsets", to unicode. It '''doesn't''' convert the the key codes
in the keymap. It also converts the input from the keyboard. Example:
'''''program (8859-1 output) --> unicode console map (unicode output) -->
font --> character on screen'''''
and:
'''''keyboard --> scancode --> kernel keymap (unicode output) --> unicode
console map (8859-1 output) --> program'''''
This conversion only takes place, if we're '''NOT''' in unicode mode. I've
tested all these things ...
----
Some comments on the examples in the book:
{{{
cat > /etc/sysconfig/console << "EOF"
# Begin /etc/sysconfig/console
KEYMAP="de-latin1"
KEYMAP_CORRECTIONS="euro2"
FONT="lat0-16 -m 8859-15"
# End /etc/sysconfig/console
EOF
}}}
'''''KEYMAP_CORRECTIONS="euro2"''''' is not necessary because de-latin1
already includes euro2.map
[[BR]]
{{{
cat > /etc/sysconfig/console << "EOF"
# Begin /etc/sysconfig/console
UNICODE="1"
KEYMAP="de-latin1"
KEYMAP_CORRECTIONS="euro2"
LEGACY_CHARSET="iso-8859-15"
FONT="LatArCyrHeb-16 -m 8859-15"
# End /etc/sysconfig/console
EOF
}}}
'''''KEYMAP_CORRECTIONS="euro2"''''' is not necessary because de-latin1
already includes euro2.map[[BR]]
'''''FONT="LatArCyrHeb-16 -m 8859-15"''''' --> "'''''-m 8859-15'''''" is
not meaningful because the kernel doesn't use this translation table in
unicode mode.
'''''LEGACY_CHARSET="iso-8859-15"''''' is not necessary because the de-
latin1 keymap doesn't contain any charset specific character code values.
The symbolic values will be converted into unicode in the right way
(without help of this conversion). See src/ksyms.c in the kbd source.
The dumpkeys man page says:
'''''-ccharset --charset=charset
This instructs dumpkeys to interpret character code values according to
the specified character set. This affects only the translation of
character code values to symbolic names. Valid values for charset
currently are iso-8859-X, Where X is a digit in 1-9. If no charset is
specified, iso-8859-1 is used as a default. This option produces an output
line 'charset "iso-8859-X"', telling loadkeys how to interpret the keymap.
(For example, "division" is 0xf7 in iso-8859-1 but 0xba in
iso-8859-8.)'''''
----
I suggest that we're adding the following examples for a german LFS into
the book:
For a system with programs that uses "legacy charsets":
{{{
cat > /etc/sysconfig/console << "EOF"
# Begin /etc/sysconfig/console
KEYMAP="de-latin1"
FONT="lat0-16 -m 8859-15"
# End /etc/sysconfig/console
EOF
}}}
For a system with no "legacy software" (only UTF-8 compatible programs):
{{{
cat > /etc/sysconfig/console << "EOF"
# Begin /etc/sysconfig/console
UNICODE="1"
KEYMAP="de-latin1"
FONT="lat0-16"
# End /etc/sysconfig/console
EOF
}}}
It should be pointed out that the "-m $charset" option is only meaningful
if "legacy software" with old charsets needs to be supported.
----
Finally, some references:
http://linux.die.net/man/1/dumpkeys
http://linux.die.net/man/8/setfont
http://www.mjmwired.net/kernel/Documentation/unicode.txt
http://gunnarwrobel.de/wiki/Linux-and-the-keyboard.html
http://freeworld.thc.org/papers/writing-linux-kernel-keylogger.txt
--
Ticket URL: <http://wiki.linuxfromscratch.org/lfs/ticket/2722>
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