67 lines
2.7 KiB
HTML
67 lines
2.7 KiB
HTML
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<TITLE>The Linux keyboard and console HOWTO: The keyboard LEDs</TITLE>
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<H2><A NAME="s10">10. The keyboard LEDs</A></H2>
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<P>
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<!--
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LEDs, keyboard
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-->
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<!--
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keyboard!LEDs on
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-->
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<P>1. There are per-tty keyboard flags:
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each VC has its own NumLock, CapsLock, ScrollLock.
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By default these keyboard flags are shown in the LEDs.
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The usual way to change them is by pressing the corresponding key.
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(Side remark: pressing the NumLock key when in application key mode
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will not change the NumLock status, but produce an escape sequence.
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If you want the NumLock key to always change the Numlock status,
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bind it to Bare_Num_Lock.)
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<P>2. Next, there are per-tty default keyboard flags,
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to initialize the keyboard flags when a reset occurs.
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Thus if you want NumLock on all the time, that is possible.
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The usual way to change them is by `<CODE>setleds -D</CODE> ...'.
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<P>3. There is the possibility that the leds do not reflect
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the keyboard flags, but something else.
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<P>3A. This something else can be three bits somewhere in the kernel -
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which can be used if you want to monitor some hardware or software
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status bit(s). If you want this, edit the kernel source to call
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<CODE>register_leds()</CODE> somewhere.
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<P>3B. This something else can also be whatever some user program wants
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to show in the LEDs. Thus, people who like such things can make
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nice patterns of lights. If you want this, use the KDSETLED ioctl.
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<P>This latter use is not per-tty, but the choice between former
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and latter use is per-tty.
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<P>Summarizing: Each tty has a flag <CODE>kbd->ledmode</CODE>.
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If this has the value LED_SHOW_FLAGS then the keyboard flags
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(NumLock etc.) of that tty are shown.
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If this has the value LED_SHOW_MEM then three selected memory
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addresses are shown.
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If this has the value LED_SHOW_IOCTL then the leds show whatever
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value was last assigned to them using the KDSETLED ioctl.
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<P>One may add that X uses ioctl's to set the LEDs, but fails
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to reset its VT when it exits, so after using X there may
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be one VT that is not in the default LED_SHOW_FLAGS state.
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This can be fixed by doing `<CODE>setleds -L</CODE>' on that VT.
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See setleds(1).
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<P>
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<HR>
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<A HREF="Keyboard-and-Console-HOWTO-11.html">Next</A>
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