The Predefined Attribute (PdAt) object class contains an entry for each existing attribute for each device represented in the Predefined Devices (PdDv) object class. An attribute, in this sense, is any device-dependent information not represented in the PdDv object class. This includes information such as interrupt levels, bus I/O address ranges, baud rates, parity settings, block sizes, and microcode file names.
Each object in this object class represents a particular attribute belonging to a particular device class-subclass-type. Each object contains the attribute name, default value, list or range of all possible values, width, flags, and an NLS description. The flags provide further information to describe an attribute.
Note: For a device being defined or configured, only the attributes that take a nondefault value are copied into the Customized Attribute (CuAt) object class. In other words, for a device being customized, if its attribute value is the default value in the PdDv object class, then there will not be an entry for the attribute in the CuAt object class.
There are three types of attributes. Most are regular attributes, which typically describe a specific attribute of a device. The group attribute type provides a grouping of regular attributes. The shared attribute type identifies devices that must all share a given attribute.
A shared attribute identifies another regular attribute as one that must be shared. This attribute is always a bus resource. Other regular attributes (for example, bus interrupt levels) can be shared by devices but are not themselves shared attributes. Shared attributes require that relevant devices have the same values for this attribute. The Attribute Value descriptor for the shared attribute gives the name of the regular attribute that must be shared.
A group attribute specifies a set of other attributes whose values are chosen as the group, as well as the group attribute number used to choose default values. Each attribute listed within a group has an associated list of possible values it can take. These values must be represented as a list, not as a range. For each attribute within the group, the list of possible values must also have the same number of choices. For example, if the possible number of values is n, the group attribute number itself can range from 0 to n-1. The particular value chosen for the group indicates the value to pick for each of the attributes in the group. For example, if the group attribute number is 0, then the value for each of the attributes in the group is the first value from their respective lists.
The Predefined Attribute object class contains the following descriptors:
|ODM Type||Descriptor Name||Description||Descriptor Status|
|ODM_CHAR||type[FLAGSIZE]||Attribute Type Flags||Required|
|ODM_CHAR||generic[FLAGSIZE]||Generic Attribute Flags||Optional|
|ODM_CHAR||rep[FLAGSIZE]||Attribute Representation Flags||Required|
These descriptors are described as follows:
|Unique Type||Identifies the class-subclass-type name of the device to which this attribute is associated. This descriptor is the same as the Unique Type descriptor in the PdDv object class.|
|Attribute Name||Identifies the name of the device attribute. This is the name that can be passed to the mkdev and chdev configuration commands and device methods in the attribute-name and attribute-value pairs.|
|Default Value|| If there are several choices or even if there is only one choice for the
attribute value, the default is the value to which the attribute is normally set. For
groups, the default value is the group attribute number. For example, if the possible
number of choices in a group is n, the group attribute number is a number
between 0 and n-1. For shared attributes, the default value is set to a null
When a device is defined in the system, attributes that take nondefault values are found in the CuAt object class. Attributes that take the default value are found in this object class; these attributes are not copied over to the CuAt object class. Therefore, both attribute object classes must be queried to get a complete set of customized attributes for a particular device.
|Attribute Values|| Identifies the possible values that can be associated with the attribute
name. The format of the value is determined by the attribute representation flags.
For regular attributes, the possible values can be represented as a string,
hexadecimal, octal, or decimal. In addition, they can be represented as either a
range or an enumerated list. If there is only one possible value, then the value can
be represented either as a single value or as an enumerated list with one entry. The
latter is recommended, since the use of enumerated lists allows the attrval subroutine to check that a given
value is in fact a possible choice.
If the value is hexadecimal, it is prefixed with the 0x notation. If the value is octal, the value is prefixed with a leading zero. If the value is decimal, its value is represented by its significant digits. If the value is a string, the string itself should not have embedded commas, since commas are used to separate items in an enumerated list.
A range is represented as a triplet of values: lowerlimit, upperlimit, and increment value. The lowerlimit variable indicates the value of the first possible choice. The upperlimit variable indicates the value of the last possible choice. The lowerlimit and upperlimit values are separated by a - (hyphen). Values between the lowerlimit and upperlimit values are obtained by adding multiples of the increment value variable to the lowerlimit variable. The upperlimit and increment value variables are separated by a comma.
|Width|| If the attribute is a regular attribute of type M for a bus memory address
or of type O for a bus I/O address, the Width descriptor can be used to identify the
amount in bytes of the bus memory or bus I/O space that must be allocated.
Alternatively, the Width
field can be set to a null string, which
indicates that the amount of bus memory or bus I/O space is specified by a width
attribute, that is, an attribute of type W.
If the attribute is a regular attribute of type W, the Width descriptor contains the name of the bus memory address or bus I/O address attribute to which this attribute corresponds. The use of a type W attribute allows the amount of bus memory or bus I/O space to be configurable, whereas if the amount is specified in the bus memory address or bus I/O address attribute's Width descriptor, it is fixed at that value and cannot be customized.
|Attribute Type|| Identifies the attribute type. Only one attribute type must be specified.
The characters A, B, M, I, N, O, P, and W represent bus resources that are regular
|Generic Attribute Flags|| Identifies the flags that can apply to any regular attribute. Any
combination (one, both, or none) of these flags is valid. This descriptor should be a
null string for group and shared attributes. This descriptor is always set to a null
string for type T attributes.
|Attribute Representation Flags|| Indicates the representation of the regular attribute values. For group
and shared attributes, which have no associated attribute representation, this
descriptor is set to a null string. Either the n or s flag, both of
which indicate value representation, must be specified.
The r, l, and m flags indicate, respectively, a range, an enumerated list, and a multi-select value list, and are optional. If neither the r flag nor the l flag is specified, the attrval subroutine will not verify that the value falls within the range or the list.
|NLS Index||Identifies the message number in the NLS message catalog of the message containing a textual description of the attribute. Only displayable attributes, as identified by the Generic Attribute Flags descriptor, need an NLS message. If the attribute is not displayable, the NLS index can be set to a value of 0. The catalog file name and the set number associated with the message number are stored in the PdDv object class.|
ODM Device Configuration Object Classes.
Predefined Devices (PdDv) object class, Customized Attribute object class.
The attrval subroutine.
The chdev command, lsattr command, mkdev command.
Adapter-Specific Considerations for the Predefined Attribute (PdAt) Object Class.