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NetBSD 6.1.5 - man page for cn_get_magic (netbsd section 9)

CNMAGIC(9)			  BSD Kernel Developer's Manual 		       CNMAGIC(9)

     cn_init_magic, cn_trap, cn_isconsole, cn_check_magic, cn_destroy_magic, cn_set_magic,
     cn_get_magic -- console magic key sequence management

     #include <sys/systm.h>

     cn_init_magic(cnm_state_t *cnms);


     cn_isconsole(dev_t dev);

     cn_check_magic(dev_t dev, int k, cnm_state_t *cnms);

     cn_destroy_magic(cnm_state_t *cnms);

     cn_set_magic(char *magic);

     cn_get_magic(char *magic, int len);

     The NetBSD console magic key sequence management framework is designed to provide flexible
     methods to set, change, and detect magic key sequences on console devices and break into the
     debugger or ROM monitor with a minimum of interrupt latency.

     Drivers that generate console input should make use of these routines.  A different
     cnm_state_t should be used for each separate input stream.  Multiple devices that share the
     same input stream, such as USB keyboards can share the same cnm_state_t.  Once a cnm_state_t
     is allocated, it should be initialized with cn_init_magic() so it can be used by
     cn_check_magic().	If a driver thinks it might be the console input device it can set the
     magic sequence with cn_set_magic() to any arbitrary string.  Whenever the driver receives
     input, it should call cn_check_magic() to process the data and determine whether the magic
     sequence has been hit.

     The magic key sequence can be accessed through the hw.cnmagic sysctl variable.  This is the
     raw data and may be keycodes rather than processed characters, depending on the console

     The following functions describe the console magic interface.

	     Initialize the console magic state pointed to by cnm to a usable state.

	     Trap into the kernel debugger or ROM monitor.  By default this routine is defined to
	     be console_debugger() but can be overridden in MI header files.

	     Determine whether a given dev is the system console.  This macro tests to see if dev
	     is the same as cn_tab->cn_dev but can be overridden in MI header files.

     cn_check_magic(dev, k, cnms)
	     All input should be passed through cn_check_magic() so the state machine remains in
	     a consistent state.  cn_check_magic() calls cn_isconsole() with dev to determine if
	     this is the console.  If that returns true then it runs the input value k through
	     the state machine.  If the state machine completes a match of the current console
	     magic sequence cn_trap() is called.  Some input may need to be translated to state
	     machine values such as the serial line BREAK sequence.

	     This should be called once what cnms points to is no longer needed.

	     cn_set_magic() encodes a nul terminated string arbitrary string into values that can
	     be used by the state machine and installs it as the global magic sequence.  The
	     escape sequence is character value 0x27 and can be used to encode special values:

		   0x27   The literal value 0x27.
		   0x01   Serial BREAK sequence.
		   0x02   Nul character.

	     Returns 0 on success or a non-zero error value.

     cn_get_magic(magic, len)
	     Extract the current magic sequence from the state machine and return up to len bytes
	     of it in the buffer pointed to by magic.  It uses the same encoding accepted by
	     cn_set_magic().  Returns 0 on success or a non-zero error value.

     sysctl(8), cons(9)

     The NetBSD console magic key sequence management framework first appeared in NetBSD 1.6.

     The NetBSD console magic key sequence management framework was designed and implemented by
     Eduardo Horvath <eeh@NetBSD.org>.

BSD					   June 8, 2010 				      BSD

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