KeyboardSupport < U-Bootdoc

%SECTION0{NAME=KeyboardSupport}% Keyboard Support

Problem: make system behaviour dependent on keys pressed at power-on

Solution: in U-Boot you can define one or more keys or key combinations and commands which are
executed when these keys are pressed at power-on:

   * ="magic_keys"= (EV) - List of characters for keys; for example:
      <verbatim>
=> setenv magic_keys 0123CB*
      </verbatim>
   * ="key_magic_?_"= (EV) - Key code or list of key codes for this action;
     scanned in the order as listed in =magic_keys=; for example:
      <verbatim>
=> setenv key_magic0 3a+3b
=> setenv key_magic1 3c
=> setenv key_magic2 4a
=> setenv key_magic3 4c+51
=> setenv key_magicC 3a+4a+5a
=> setenv key_magicB 52+53
=> setenv key_magic* 55+56
      </verbatim>
   * ="key_cmd?"= (EV) - Action to be performed when corresponding key(s) are pressed; for example:
      <verbatim>
=> setenv key_cmd0 setenv bootdelay 10
=> setenv key_cmd1 setenv addcons 'console=ttyS0,${baudrate}'
=> setenv key_cmd2 setenv memtest on
=> setenv key_cmd3 setenv bootcmd run old_version
=> setenv key_cmdC setenv bootcmd run recovery
=> setenv key_cmdB setenv bootcmd run usb_update
=> setenv key_cmd* setenv bootcmd run demo_mode
      </verbatim>

Example: after a software update, the user can select to boot the old software version
("run old_version")
by holding the keys with keycodes "4c" and "51" at power-on.
1.12.2. Boot Count Limit		1. Abstract		1.12.4. Automatic Updates
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