DESCRIPTION
The file
/dev/openprom is an interface to the SPARC OPENPROM, including the EEPROM area. This interface is highly stylized; ioctls are used for all operations. These ioctls refer to “nodes”, which are simply “magic” integer values describing data areas. Occasionally the number 0 may be used or returned instead, as described below. A special distinguished “options” node holds the EEPROM settings.
The calls that take and/or return a node use a pointer to an int
variable for this purpose; others use a pointer to an struct opiocdesc
descriptor, which contains a node and two counted strings. The first string comprises the fields op_namelen
(an int
) and op_name
(a char *
), giving the name of a field. The second string comprises the fields op_buflen
and op_buf
, used analogously. These two counted strings work in a “value-result” fashion. At entry to the ioctl, the counts are expected to reflect the buffer size; on return, the counts are updated to reflect the buffer contents.
The following ioctls are supported:
-
OPIOCGETOPTNODE
-
Takes nothing, and fills in the options node number.
-
OPIOCGETNEXT
-
Takes a node number and returns the number of the following node. The node following the last node is number 0; the node following number 0 is the first node.
-
OPIOCGETCHILD
-
Takes a node number and returns the number of the first “child” of that node. This child may have siblings; these can be discovered by using OPIOCGETNEXT.
-
OPIOCGET
-
Fills in the value of the named property for the given node. If no such property is associated with that node, the value length is set to -1. If the named property exists but has no value, the value length is set to 0.
-
OPIOCSET
-
Writes the given value under the given name. The OPENPROM may refuse this operation; in this case EINVAL is returned.
-
OPIOCNEXTPROP
-
Finds the property whose name follows the given name in OPENPROM internal order. The resulting name is returned in the value field. If the named property is the last, the “next” name is the empty string. As with OPIOCGETNEXT, the next name after the empty string is the first name.
BUGS
Due to limitations within the
openprom itself, these functions run at elevated priority and may adversely affect system performance.
The Sun openprom is what became the Open Firmware (IEEE 1275) standard for processor and system independent boot firmware.