Directives

25.3. Directives#

This section details the directives of the User Extensions Manager. A subsection is dedicated to each of this manager’s directives and lists the calling sequence, parameters, description, return values, and notes of the directive.

25.3.1. rtems_extension_create()#

Creates an extension set.

CALLING SEQUENCE:

rtems_status_code rtems_extension_create(
  rtems_name                    name,
  const rtems_extensions_table *extension_table,
  rtems_id                     *id
);

PARAMETERS:

name

This parameter is the object name of the extension set.

extension_table

This parameter is the table with the extensions to be used by the extension set.

id

This parameter is the pointer to an rtems_id object. When the directive call is successful, the identifier of the created extension set will be stored in this object.

DESCRIPTION:

This directive creates an extension set which resides on the local node. The extension set has the user-defined object name specified in name. The assigned object identifier is returned in id. This identifier is used to access the extension set with other extension set related directives.

The extension set is initialized using the extension table specified in extension_table.

RETURN VALUES:

RTEMS_SUCCESSFUL

The requested operation was successful.

RTEMS_INVALID_NAME

The name parameter was invalid.

RTEMS_INVALID_ADDRESS

The extension_table parameter was NULL.

RTEMS_INVALID_ADDRESS

The id parameter was NULL.

RTEMS_TOO_MANY

There was no inactive object available to create an extension set. The number of extension sets available to the application is configured through the CONFIGURE_MAXIMUM_USER_EXTENSIONS application configuration option.

NOTES:

The user-provided extension table is not used after the return of the directive.

Each extension of the extension table is optional and may be NULL. All extensions except the task switch extension of the extension table are atomically and immediately installed. A task switch extension is separately installed after the other extensions. The extensions of the extension table are invoked upon the next system event supporting an extension.

An alternative to dynamically created extension sets are initial extensions, see CONFIGURE_INITIAL_EXTENSIONS. Initial extensions are recommended for extension sets which provide a fatal error extension.

For control and maintenance of the extension set, RTEMS allocates a ESCB from the local ESCB free pool and initializes it.

CONSTRAINTS:

The following constraints apply to this directive:

  • The directive may be called from within device driver initialization context.

  • The directive may be called from within task context.

  • The directive may obtain and release the object allocator mutex. This may cause the calling task to be preempted.

  • The number of extension sets available to the application is configured through the CONFIGURE_MAXIMUM_USER_EXTENSIONS application configuration option.

25.3.2. rtems_extension_delete()#

Deletes the extension set.

CALLING SEQUENCE:

rtems_status_code rtems_extension_delete( rtems_id id );

PARAMETERS:

id

This parameter is the extension set identifier.

DESCRIPTION:

This directive deletes the extension set specified by id.

RETURN VALUES:

RTEMS_SUCCESSFUL

The requested operation was successful.

RTEMS_INVALID_ID

There was no extension set associated with the identifier specified by id.

NOTES:

The ESCB for the deleted extension set is reclaimed by RTEMS.

CONSTRAINTS:

The following constraints apply to this directive:

  • The directive may be called from within device driver initialization context.

  • The directive may be called from within task context.

  • The directive may obtain and release the object allocator mutex. This may cause the calling task to be preempted.

  • The calling task does not have to be the task that created the object. Any local task that knows the object identifier can delete the object.

25.3.3. rtems_extension_ident()#

Identifies an extension set by the object name.

CALLING SEQUENCE:

rtems_status_code rtems_extension_ident( rtems_name name, rtems_id *id );

PARAMETERS:

name

This parameter is the object name to look up.

id

This parameter is the pointer to an rtems_id object. When the directive call is successful, the object identifier of an object with the specified name will be stored in this object.

DESCRIPTION:

This directive obtains an extension set identifier associated with the extension set name specified in name.

RETURN VALUES:

RTEMS_SUCCESSFUL

The requested operation was successful.

RTEMS_INVALID_ADDRESS

The id parameter was NULL.

RTEMS_INVALID_NAME

The name parameter was 0.

RTEMS_INVALID_NAME

There was no object with the specified name on the local node.

NOTES:

If the extension set name is not unique, then the extension set identifier will match the first extension set with that name in the search order. However, this extension set identifier is not guaranteed to correspond to the desired extension set.

The objects are searched from lowest to the highest index. Only the local node is searched.

The extension set identifier is used with other extension related directives to access the extension set.

CONSTRAINTS:

The following constraints apply to this directive:

  • The directive may be called from within device driver initialization context.

  • The directive will not cause the calling task to be preempted.