[job] Allow job_progress() to return an ongoing job status code, if known

Some background jobs have a meaningful ongoing status code (e.g. the
current link status for a job waiting for a network link to come up).
Allow this to be exposed via the job_progress() method.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/core/downloader.c

  *
  * @v downloader	Downloader
  * @v progress		Progress report to fill in
+ * @ret ongoing_rc	Ongoing job status code (if known)
  */
-static void downloader_progress ( struct downloader *downloader,
-				  struct job_progress *progress ) {
+static int downloader_progress ( struct downloader *downloader,
+				 struct job_progress *progress ) {
 
 	/* This is not entirely accurate, since downloaded data may
 	 * arrive out of order (e.g. with multicast protocols), but
 	 */
 	progress->completed = downloader->pos;
 	progress->total = downloader->image->len;
+
+	return 0;
 }
 
 /****************************************************************************

src/core/job.c

  *
  * @v intf		Object interface
  * @v progress		Progress data to fill in
+ * @ret ongoing_rc	Ongoing job status code (if known)
  */
-void job_progress ( struct interface *intf, struct job_progress *progress ) {
+int job_progress ( struct interface *intf, struct job_progress *progress ) {
 	struct interface *dest;
 	job_progress_TYPE ( void * ) *op =
 		intf_get_dest_op ( intf, job_progress, &dest );
 	void *object = intf_object ( dest );
+	int ongoing_rc;
 
 	DBGC ( INTF_COL ( intf ), "INTF " INTF_INTF_FMT " job_progress\n",
 	       INTF_INTF_DBG ( intf, dest ) );
 
+	/* Initialise progress to zero */
+	memset ( progress, 0, sizeof ( *progress ) );
+
 	if ( op ) {
-		op ( object, progress );
+		ongoing_rc = op ( object, progress );
 	} else {
-		/* Default is to mark progress as zero */
-		memset ( progress, 0, sizeof ( *progress ) );
+		/* Default is to leave progress as zero and have no
+		 * known return status code.
+		 */
+		ongoing_rc = 0;
 	}
 
 	intf_put ( dest );
+	return ongoing_rc;
 }

src/include/ipxe/job.h

 	unsigned long total;
 };
 
-extern void job_progress ( struct interface *intf,
-			   struct job_progress *progress );
+extern int job_progress ( struct interface *intf,
+			  struct job_progress *progress );
 #define job_progress_TYPE( object_type ) \
-	typeof ( void ( object_type, struct job_progress *progress ) )
+	typeof ( int ( object_type, struct job_progress *progress ) )
 
 #endif /* _IPXE_JOB_H */