MK48TXX(4) BSD Kernel Interfaces Manual MK48TXX(4)NAMEmk48txx — 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 mk48txxDESCRIPTION
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 ALSOintro(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
