The cram driver provides an interface to
the 64 bytes of battery backed-up
RAM. This memory contains information such as diagnostics and
configuration information.
The following ioctl calls apply:
CMOSREAD
This call is used to read the contents of
one of the CMOS RAM locations.
The
argument to the ioctl is the address of
a buffer of two unsigned characters,
the first of which is the address to be read.
The ioctl will fill in the
second byte with the data.
An address less than 0 or greater than 63 will
result in an error, with
errno
set to ENXIO.
CMOSWRITE
This call is used to write a value into
one of the CMOS RAM locations.
The
argument to the ioctl is the address
of a buffer of two unsigned characters,
the first of which is the address and the second of which is
the value to write at that address.
An address less than 0 or greater than
63 will result in an error, with
errno
set to ENXIO.
Note that only the superuser may open the CMOS RAM
device for writing, and that the
CMOSWRITEioctl will fail for any other than
the superuser.