Questions about the Linux console keyboard driver / translation tables


 
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Old 03-10-2012
Questions about the Linux console keyboard driver / translation tables

Hi there,

I am trying to understand the logic of the Linux keyboard driver, I am not sure if this is the right place to ask, but I don't know where else I could.

Btw. I am talking about an unicode console here.

1.) The Linux kernel (currently) can take 256 translation tables (keymaps), I figured that if I have 8 Mod-Keys and I can press two at the same time, then this makes 256 possible modifications.
E.g. the value of my keycode of the button 'a' is 0x0b61 (small letter a) in table 0 and 0x0b41 (capital letter A) in table 1, so is it true that table 1 is for shift pressed keycodes?
If so, then why is shift (KG_SHIFT in linux/keyboard.h) set to 0, and how do I compute the modifications, meaning how do I know what e.g. index 231 represents?

2.) As seen above, the value for 'a' is actually 0x0b61 instead of 0x0061, if b indicates a type (here KT_LOCK) why isn't it 0xfb61, because I thought that only values above 0xf000 represent typed values, and the values below are simply unicode values.
The values above are read via the KDGKBENT ioctl, are these values read differently then written?
E.g. would I only type 0xfb61 when using the KDSKBENT ioctl?

I hope anyone can help me out a little,
thank you very much in advance,
regards,
Bill
 
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UKBD(4) 						   BSD Kernel Interfaces Manual 						   UKBD(4)

NAME
ukbd -- USB keyboard driver SYNOPSIS
To compile this driver into the kernel, place the following line in your kernel configuration file: device ukbd Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5): ukbd_load="YES" DESCRIPTION
The ukbd driver provides support for keyboards that attach to the USB port. usb(4) and one of uhci(4) or ohci(4) must be configured in the kernel as well. CONFIGURATION
By default, the keyboard subsystem does not create the appropriate devices yet. Make sure you reconfigure your kernel with the following option in the kernel config file: options KBD_INSTALL_CDEV If both an AT keyboard USB keyboards are used at the same time, the AT keyboard will appear as kbd0 in /dev. The USB keyboards will be kbd1, kbd2, etc. You can see some information about the keyboard with the following command: kbdcontrol -i < /dev/kbd1 or load a keymap with kbdcontrol -l keymaps/pt.iso < /dev/kbd1 See kbdcontrol(1) for more possible options. You can swap console keyboards by using the command kbdcontrol -k /dev/kbd1 From this point on, the first USB keyboard will be the keyboard to be used by the console. If you want to use a USB keyboard as your default and not use an AT keyboard at all, you will have to remove the device atkbd line from the kernel configuration file. Because of the device initialization order, the USB keyboard will be detected after the console driver initial- izes itself and you have to explicitly tell the console driver to use the existence of the USB keyboard. This can be done in one of the fol- lowing two ways. Run the following command as a part of system initialization: kbdcontrol -k /dev/kbd0 < /dev/ttyv0 > /dev/null (Note that as the USB keyboard is the only keyboard, it is accessed as /dev/kbd0) or otherwise tell the console driver to periodically look for a keyboard by setting a flag in the kernel configuration file: device sc0 at isa? flags 0x100 With the above flag, the console driver will try to detect any keyboard in the system if it did not detect one while it was initialized at boot time. DRIVER CONFIGURATION
options KBD_INSTALL_CDEV Make the keyboards available through a character device in /dev. options UKBD_DFLT_KEYMAP makeoptions UKBD_DFLT_KEYMAP=fr.iso The above lines will put the French ISO keymap in the ukbd driver. You can specify any keymap in /usr/share/syscons/keymaps with this option. options KBD_DISABLE_KEYMAP_LOADING Do not allow the user to change the keymap. Note that these options also affect the AT keyboard driver, atkbd(4). FILES
/dev/kbd* blocking device nodes EXAMPLES
device ukbd Add the ukbd driver to the kernel. SEE ALSO
kbdcontrol(1), ohci(4), syscons(4), uhci(4), usb(4), config(8) AUTHORS
The ukbd driver was written by Lennart Augustsson <augustss@cs.chalmers.se> for NetBSD and was substantially rewritten for FreeBSD by Kazutaka YOKOTA <yokota@zodiac.mech.utsunomiya-u.ac.jp>. This manual page was written by Nick Hibma <n_hibma@FreeBSD.org> with a large amount of input from Kazutaka YOKOTA <yokota@zodiac.mech.utsunomiya-u.ac.jp>. BSD
November 22, 2006 BSD