OPENPROM(4D) Devices OPENPROM(4D)

NAME

openprom - PROM monitor configuration interface

SYNOPSIS

#include <sys/fcntl.h>


#include <sys/types.h>


#include <sys/openpromio.h>


open("/dev/openprom", mode);

DESCRIPTION

The internal encoding of the configuration information stored in
EEPROM or NVRAM varies from model to model, and on some systems the
encoding is "hidden" by the firmware. The openprom driver provides a
consistent interface that allows a user or program to inspect and
modify that configuration, using ioctl(2) requests. These requests
are defined in <sys/openpromio.h>:

struct openpromio {
uint_t oprom_size; /* real size of following data */
union {
char b[1]; /* NB: Adjacent, Null terminated */
int i;
} opio_u;
};
#define oprom_array opio_u.b /* property name/value array */
#define oprom_node opio_u.i /* nodeid from navigation config-ops */
#define oprom_len opio_u.i /* property len from OPROMGETPROPLEN */
#define OPROMMAXPARAM 32768 /* max size of array (advisory) */


For all ioctl(2) requests, the third parameter is a pointer to a
struct openpromio. All property names and values are null-terminated
strings; the value of a numeric option is its ASCII representation.


For the raw ioctl(2) operations shown below that explicitly or
implicitly specify a nodeid, an error may be returned. This is due to
the removal of the node from the firmware device tree by a Dynamic
Reconfiguration operation. Programs should decide if the appropriate
response is to restart the scanning operation from the beginning or
terminate, informing the user that the tree has changed.

IOCTLS

OPROMGETOPT
This ioctl takes the null-terminated name of a
property in the oprom_array and returns its null-
terminated value (overlaying its name).
oprom_size should be set to the size of
oprom_array; on return it will contain the size of
the returned value. If the named property does not
exist, or if there is not enough space to hold its
value, then oprom_size will be set to zero. See
BUGS below.


OPROMSETOPT
This ioctl takes two adjacent strings in
oprom_array; the null-terminated property name
followed by the null-terminated value.


OPROMSETOPT2
This ioctl is similar to OPROMSETOPT, except that
it uses the difference between the actual user
array size and the length of the property name
plus its null terminator.


OPROMNXTOPT
This ioctl is used to retrieve properties
sequentially. The null-terminated name of a
property is placed into oprom_array and on return
it is replaced with the null-terminated name of
the next property in the sequence, with oprom_size
set to its length. A null string on input means
return the name of the first property; an
oprom_size of zero on output means there are no
more properties.


OPROMNXT
OPROMCHILD
OPROMGETPROP
OPROMNXTPROP
These ioctls provide an interface to the raw
config_ops operations in the PROM monitor. One can
use them to traverse the system device tree; see
prtconf(8).


OPROMGETPROPLEN
This ioctl provides an interface to the property
length raw config op. It takes the name of a
property in the buffer, and returns an integer in
the buffer. It returns the integer -1 if the
property does not exist; 0 if the property exists,
but has no value (a boolean property); or a
positive integer which is the length of the
property as reported by the PROM monitor. See BUGS
below.


OPROMGETVERSION
This ioctl returns an arbitrary and platform-
dependent NULL-terminated string in oprom_array,
representing the underlying version of the
firmware.

ERRORS

EAGAIN
There are too many opens of the /dev/openprom device.


EFAULT
A bad address has been passed to an ioctl(2) routine.


EINVAL
The size value was invalid, or (for OPROMSETOPT) the
property does not exist, or an invalid ioctl is being
issued, or the ioctl is not supported by the firmware, or
the nodeid specified does not exist in the firmware device
tree.


ENOMEM
The kernel could not allocate space to copy the user's
structure.


EPERM
Attempts have been made to write to a read-only entity, or
read from a write only entity.


ENXIO
Attempting to open a non-existent device.

EXAMPLES

Example 1: oprom_array Data Allocation and Reuse

The following example shows how the oprom_array is allocated and
reused for data returned by the driver.


/*
* This program opens the openprom device and prints the platform
* name (root node name property) and the prom version.
*
* NOTE: /dev/openprom is readable only by user 'root' or group 'sys'.
*/
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/openpromio.h>
#define min(a, b) (a < b ? a : b)
#define max(a, b) (a > b ? a : b)
#define MAXNAMESZ 32 /* Maximum property *name* size */
#define BUFSZ 1024 /* A Handly default buffer size */
#define MAXVALSZ (BUFSZ - sizeof (int))
static char *promdev = "/dev/openprom";
/*
* Allocate an openpromio structure big enough to contain
* a bufsize'd oprom_array. Zero out the structure and
* set the oprom_size field to bufsize.
*/
static struct openpromio *
opp_zalloc(size_t bufsize)
{
struct openpromio *opp;
opp = malloc(sizeof (struct openpromio) + bufsize);
(void) memset(opp, 0, sizeof (struct openpromio) + bufsize);
opp->oprom_size = bufsize;
return (opp);
}
/*
* Free a 'struct openpromio' allocated by opp_zalloc
*/
static void
opp_free(struct openpromio *opp)
{
free(opp);
}
/*
* Get the peer node of the given node. The root node is the peer of zero.
* After changing nodes, property lookups apply to that node. The driver
* 'remembers' what node you are in.
*/
static int
peer(int nodeid, int fd)
{
struct openpromio *opp;
int i;
opp = opp_zalloc(sizeof (int));
opp->oprom_node = nodeid;
if (ioctl(fd, OPROMNEXT, opp) < 0) {
perror("OPROMNEXT");
exit(1);
}
i = opp->oprom_node;
opp_free(opp);
return(i);
}
int
main(void)
{
struct openpromio *opp;
int fd, proplen;
size_t buflen;
if ((fd = open(promdev, O_RDONLY)) < 0) {
fprintf(stderr, "Cannot open openprom device\n");
exit(1);
}
/*
* Get and print the length and value of the
* root node 'name' property
*/
(void) peer(0, fd); /* Navigate to the root node */
/*
* Allocate an openpromio structure sized big enough to
* take the string "name" as input and return the int-sized
* length of the 'name' property.
* Then, get the length of the 'name' property.
*/
buflen = max(sizeof (int), strlen("name") + 1);
opp = opp_zalloc(buflen);
(void) strcpy(opp->oprom_array, "name");
if (ioctl(fd, OPROMGETPROPLEN, opp) < 0) {
perror("OPROMGETPROPLEN");
/* exit(1); */
proplen = 0; /* down-rev driver? */
} else
proplen = opp->oprom_len;
opp_free(opp);
if (proplen == -1) {
printf("'name' property does not exist!\n");
exit (1);
}
/*
* Allocate an openpromio structure sized big enough
* to take the string 'name' as input and to return
* 'proplen + 1' bytes. Then, get the value of the
* 'name' property. Note how we make sure to size the
* array at least one byte more than the returned length
* to guarantee NULL termination.
*/
buflen = (proplen ? proplen + 1 : MAXVALSZ);
buflen = max(buflen, strlen("name") + 1);
opp = opp_zalloc(buflen);
(void) strcpy(opp->oprom_array, "name");
if (ioctl(fd, OPROMGETPROP, opp) < 0) {
perror("OPROMGETPROP");
exit(1);
}
if (opp->oprom_size != 0)
printf("Platform name <%s> property len <%d>\n",
opp->oprom_array, proplen);
opp_free(opp);
/*
* Allocate an openpromio structure assumed to be
* big enough to get the 'prom version string'.
* Get and print the prom version.
*/
opp_zalloc(MAXVALSZ);
opp->oprom_size = MAXVALSZ;
if (ioctl(fd, OPROMGETVERSION, opp) < 0) {
perror("OPROMGETVERSION");
exit(1);
}
printf("Prom version <%s>\n", opp->oprom_array);
opp_free(opp);
(void) close(fd);
return (0);
}

FILES

/dev/openprom
PROM monitor configuration interface

SEE ALSO

ioctl(2), mem(4D), eeprom(8), prtconf(8)

BUGS

There should be separate return values for non-existent properties as
opposed to not enough space for the value.


An attempt to set a property to an illegal value results in the PROM
setting it to some legal value, with no error being returned. An
OPROMGETOPT should be performed after an OPROMSETOPT to verify that
the set worked.


Some PROMS lie about the property length of some string properties,
omitting the NULL terminator from the property length. The openprom
driver attempts to transparently compensate for these bugs when
returning property values by NULL terminating an extra character in
the user buffer if space is available in the user buffer. This extra
character is excluded from the oprom_size field returned from
OPROMGETPROP and OPROMGETOPT and excluded in the oprom_len field
returned from OPROMGETPROPLEN but is returned in the user buffer from
the calls that return data, if the user buffer is allocated at least
one byte larger than the property length.

March 6, 2023 OPENPROM(4D)