mk48txx man page on FreeBSD

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

NAME
     mk48txx — Mostek time-of-day clock driver

SYNOPSIS
     #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

DESCRIPTION
     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
	     below).

     sc_model
	     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.

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

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

     sc_year0
	     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
	     dependent on the system configuration in which the clock device
	     is mounted.  For instance, on Sun Microsystems machines the con‐
	     vention is to have clock's two-digit year represent the year
	     since 1968.

     sc_flag
	     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 9(watchdog) 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).

     sc_nvread

     sc_nvwrite
	     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
	     resource.

	     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.

HARDWARE
     The following models are supported:

	   Mostek MK48T02
	   Mostek MK48T08
	   Mostek MK48T18
	   Mostek MK48T59

SEE ALSO
     intro(4), watchdog(9)

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

AUTHORS
     The mk48txx driver was written for NetBSD by Paul Kranenburg
     ⟨pk@NetBSD.org⟩.  It was ported to FreeBSD by Thomas Moestl
     ⟨tmm@FreeBSD.org⟩ and later on improved by Marius Strobl
     ⟨marius@FreeBSD.org⟩.

BSD			       December 25, 2009			   BSD
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