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MK48TXX(4)		 BSD Kernel Interfaces Manual		    MK48TXX(4)

     mk48txx --	Mostek time-of-day clock driver

     #include <sys/eventhandler.h>
     #include <sys/lock.h>
     #include <sys/mutex.h>
     #include <dev/mk48txx/mk48txxvar.h>

     To	compile	this driver into the kernel, place the following line in your
     kernel configuration file:

	   device mk48txx

     The mk48txx driver	is a back-end for several models of Mostek time-of-day
     clock chips.  It provides access methods to retrieve and set date and
     time for use with the "clock" KOBJ	interface.

     To	tie an instance	of this	device to the system, use the mk48txx_attach()
     function and the mk48txx_softc structure defined as follows:

     int mk48txx_attach(device_t dev)

     typedef uint8_t (*mk48txx_nvrd_t)(device_t	dev, int off);
     typedef void (*mk48txx_nvwr_t)(device_t dev, int off, uint8_t v);

     struct mk48txx_softc {
	     struct resource sc_res;
	     struct mtx	     sc_mtx;
	     eventhandler_tag	     sc_wet;
	     const char	     *sc_model;
	     bus_size_t	     sc_nvramsz;
	     bus_size_t	     sc_clkoffset;
	     u_int	     sc_year0;
	     u_int	     sc_flag;
	     mk48txx_nvrd_t  sc_nvrd;
	     mk48txx_nvwr_t  sc_nvwr;

     sc_res  The bus resource used for accessing the chip's non-volatile mem-
	     ory (including the	clock registers), which	must be	supplied by
	     the front-end when	using the default access methods (see below).
	     Otherwise this member is optional.

     sc_mtx  The hardware mutex	used when accessing the	chip's non-volatile
	     memory (including the clock registers), which must	be initialized
	     with MTX_DEF by the front-end.

     sc_wet  The event handler tag for the watchdog functionality, which is
	     registered	by the mk48txx_attach()	function if supported by the
	     chip and specified	as part	of the machine-dependent features (see

	     The chip model which this instance	should serve.  This member
	     must be set to one	of "mk48t02", "mk48t08", "mk48t18", or
	     "mk48t59" by the front-end.

	     The size of the non-volatile RAM in the Mostek chip, which	is set
	     by	the mk48txx_attach() function.

	     The offset	into the control registers of the Mostek chip, which
	     is	set by the mk48txx_attach() function.

	     The year offset to	be used	with the `year'	counter	of the clock,
	     which must	be set by the front-end.  This value is	generally de-
	     pendent on	the system configuration in which the clock device is
	     mounted.  For instance, on	Sun Microsystems machines the conven-
	     tion is to	have clock's two-digit year represent the year since

	     This flag is used to specify machine-dependent features.  The
	     following flags are supported:

	     MK48TXX_NO_CENT_ADJUST   If the resulting date retrieved with the
				      "clock_gettime() method" would be	ear-
				      lier than	January	1, 1970, the driver
				      will assume that the chip's year counter
				      actually represents a year in the	21st
				      century.	This behavior can be overrid-
				      den by setting this flag,	which causes
				      the mk48txx driver to respect the
				      clock's century bit instead.

	     MK48TXX_WDOG_REGISTER    When this	flag is	set, the mk48txx
				      driver will register as a	watchdog via
				      the interface defined in watchdog(9) if
				      supported	by the specific	chip model.

	     MK48TXX_WDOG_ENABLE_WDS  When this	flag is	set, the mk48txx
				      driver will set the watchdog steering
				      (WDS) bit	when enabling the watchdog
				      functionality of the chip.  enabled (see
				      the chip documentation for further
				      information regarding the	WDS bit).


	     These members specify the access methods for reading respectively
	     writing clock device registers.  The default, when	NULL is	passed
	     as	an access method, is to	access the chip	memory (and clock
	     registers)	as if they were	direct-mapped using the	specified bus

	     Otherwise,	the driver will	call the respective function supplied
	     by	the front-end to perform the access, passing it	the offset off
	     of	the chip memory	(or clock register) location to	be read	from
	     or	written	to, respectively.

     The following models are supported:

	   Mostek MK48T02
	   Mostek MK48T08
	   Mostek MK48T18
	   Mostek MK48T59

     intro(4), watchdog(9)

     The mk48txx driver	appeared in NetBSD 1.5.	 The first FreeBSD version to
     include it	was FreeBSD 5.0.

     The mk48txx driver	was written for	NetBSD by Paul Kranenburg
     <>.  It was ported to	FreeBSD	by Thomas Moestl
     <> and later on improved by	Marius Strobl

BSD			       December	25, 2009			   BSD


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