'\"macro stdmacro
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.TH PMDADSO 3 "PCP" "Performance Co-Pilot"
.SH NAME
\f3pmdaDSO\f1 \- initialize the PMDA to run as a DSO
.SH "C SYNOPSIS"
.ft 3
#include <pcp/pmapi.h>
.br
#include <pcp/pmda.h>
.sp
.ad l
.hy 0
.in +8n
.ti -8n
int pmdaDSO(pmdaInterface *\fIdispatch\fP, int \fIinterface\fP, char\ *\fIname\fP, char\ *\fIhelptext\fP);
.sp
.in
.hy
.ad
cc ... \-lpcp_pmda \-lpcp
.ft 1
.SH DESCRIPTION
.B pmdaDSO
initializes the
.B pmdaInterface
structure to use the
.I interface
extensions,
assuming the
.BR PMDA (3)
is to be run as a DSO.  The
.B pmdaInterface
structure is initialized with:
.TP 15
.I name
The name of the agent.
.TP
.I helptext
The default path to the help text (see
.BR pmdaText (3)).
If no help text is installed, or you are not using
.BR pmdaText (3),
then this should be set to NULL, otherwise
.I helptext
will be copied, so the storage associated with
.I helptext
may be released after the call to
.BR pmdaDSO .
.PP
The callbacks are initialized to
.BR pmdaProfile (3),
.BR pmdaFetch (3),
.BR pmdaDesc (3),
.BR pmdaText (3),
.BR pmdaInstance (3)
and
.BR pmdaStore (3).
.PP
The
.I interface
structure also contains the
.I domain
of the
.BR PMDA (3),
which is defined in the
.BR pmcd (1)
configuration file. The
.I domain
is used to initialize the metric and instance descriptors (see
.BR pmdaInit (3)).
.SH CAVEAT
The PMDA must be using
.B PMDA_INTERFACE_2
or later.
.PP
Once
.B pmdaDSO
has been called, it is expected that the
.B pmdaInterface
structure pointed to by
.I dispatch
will remain accessible to the
routines in
.I libpcp_pmda
(not reclaimed off the stack,
not freed or oherwise released, etc.).
If the caller needs to move or relocate the
.B pmdaInterface
structure for any reason, then after the move
.BR pmdaInterfaceMoved (3)
must be called to resestablish the internal integrity of the
.I pmdaInterface
structure at the new location before any other routine in
.I libpcp_pmda
is called.
.SH DIAGNOSTICS
.TP 15
.B Incompatible version of pmcd detected
When
.BR pmcd (1)
creates the
.B pmdaInterface
structure, the
.I dispatch.comm.version
field is set to the highest protocol that
.BR pmcd (1)
understands.  This message indicates that the
.BR pmcd (1)
process does not understand the protocol used by
.BR pmdaDSO .
.TP
.B Unable to allocate memory for pmdaExt structure
In addition,
.I dispatch->status
is set to a value less than zero.
.SH SEE ALSO
.BR pmcd (1),
.BR PMAPI (3),
.BR PMDA (3),
.BR pmdaDaemon (3),
.BR pmdaInit (3),
.BR pmdaInterfaceMoved (3)
and
.BR pmdaText (3).