LIBPICLTREE(3PICLTREE) PICL Plug-In Library Functions LIBPICLTREE(3PICLTREE)

NAME

libpicltree - PTree and Plug-in Registration interface library

SYNOPSIS

cc [flag ...] file ... -lpicltree [library ...]
#include <picltree.h>

DESCRIPTION

The PTree interface is the set of functions and data structures to access
and manipulate the PICL tree. The daemon and the plug-in modules use the
PTree interface.


The Plug-in Registration interface is used by the plug-in modules to
register themselves with the daemon.


The plug-in modules create the nodes and properties of the tree. At the
time of creating a property, the plug-ins specify the property
information in the ptree_propinfo_t structure defined as:

typedef struct {
int version; /* version */
picl_propinfo_t piclinfo; /* info to clients */
int (*read)(ptree_rarg_t *arg, void *buf);
/* read access function for */
/* volatile prop */
int (*write)(ptree_warg_t *arg, const void *buf);
/* write access function for */
/* volatile prop */
} ptree_propinfo_t;


See libpicl(3PICL) for more information on PICL tree nodes and
properties.


The maximum size of a property value cannot exceed PICL_PROPSIZE_MAX. It
is currently set to 512KB.

Volatile Properties

In addition to PICL_READ and PICL_WRITE property access modes, the plug-
in modules specify whether a property is volatile or not by setting the
bit PICL_VOLATILE.

#define PICL_VOLATILE 0x4


For a volatile property, the plug-in module provides the access functions
to read and/or write the property in the ptree_propinfo_t argument passed
when creating the property.


The daemon invokes the access functions of volatile properties when
clients access their values. Two arguments are passed to the read access
functions. The first argument is a pointer to ptree_rarg_t, which
contains the handle of the node, the handle of the accessed property and
the credentials of the caller. The second argument is a pointer to the
buffer where the value is to be copied.

typedef struct {
picl_nodehdl_t nodeh;
picl_prophdl_t proph;
door_cred_t cred;
} ptree_rarg_t;


The prototype of the read access function for volatile property is:

int read(ptree_rarg_t *rarg, void *buf);


The read function returns PICL_SUCCESS to indicate successful completion.


Similarly, when a write access is performed on a volatile property, the
daemon invokes the write access function provided by the plug-in for that
property and passes it two arguments. The first argument is a pointer to
ptree_warg_t, which contains the handle to the node, the handle of the
accessed property and the credentials of the caller. The second argument
is a pointer to the buffer containing the value to be written.

typedef struct {
picl_nodehdl_t nodeh;
picl_prophdl_t proph;
door_cred_t cred;
} ptree_warg_t;


The prototype of the write access function for volatile property is:

int write(ptree_warg_t *warg, const void *buf);


The write function returns PICL_SUCCESS to indicate successful
completion.


For all volatile properties, the 'size' of the property must be specified
to be the maximum possible size of the value. The maximum size of the
value cannot exceed PICL_PROPSIZE_MAX. This allows a client to allocate a
sufficiently large buffer before retrieving a volatile property's value.

Plug-in Modules
Plug-in modules are shared objects that are located in well-known
directories for the daemon to locate and load them. Plug-in modules are
located in one of the following plug-in directories depending on the
platform-specific nature of the data they collect and publish.

/usr/platform/picl/plugins/`uname -i`/
/usr/platform/picl/plugins/`uname -m`/
/usr/lib/picl/plugins/


A plug-in module may specify its dependency on another plug-in module
using the -l linker option. The plug-ins are loaded by the PICL daemon
using dlopen(3C) according to the specified dependencies. Each plug-in
module must define a .init section, which is executed when the plug-in
module is loaded, to register themselves with the daemon. See
picld_plugin_register(3PICLTREE) for more information on plug-in
registration.


The plug-in modules may use the picld_log(3PICLTREE) function to log
their messages to the system log file.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+---------------+-----------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+-----------------+
|MT-Level | MT-Safe |
+---------------+-----------------+

SEE ALSO

libpicltree(3LIB), libpicl(3PICL), picld_log(3PICLTREE),
picld_plugin_register(3PICLTREE), attributes(7)

September 12, 2020 LIBPICLTREE(3PICLTREE)