[process] Pass containing object pointer to process step() methods

Give the step() method a pointer to the containing object, rather than
a pointer to the process.  This is consistent with the operation of
interface methods, and allows a single function to serve as both an
interface method and a process step() method.

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

src/include/ipxe/process.h

@@ -17,6 +17,20 @@ FILE_LICENCE ( GPL2_OR_LATER );
 struct process {
 	/** List of processes */
 	struct list_head list;
+	/** Process descriptor */
+	struct process_descriptor *desc;
+	/** Reference counter
+	 *
+	 * If this process is not part of a reference-counted object,
+	 * this field may be NULL.
+	 */
+	struct refcnt *refcnt;
+};
+
+/** A process descriptor */
+struct process_descriptor {
+	/** Offset of process within containing object */
+	size_t offset;
 	/**
 	 * Single-step the process
 	 *
@@ -24,15 +38,63 @@ struct process {
 	 * Returning from this method is isomorphic to yielding the
 	 * CPU to another process.
 	 */
-	void ( * step ) ( struct process *process );
-	/** Reference counter
-	 *
-	 * If this interface is not part of a reference-counted
-	 * object, this field may be NULL.
-	 */
-	struct refcnt *refcnt;
+	void ( * step ) ( void *object );
 };
 
+/**
+ * Define a process step() method
+ *
+ * @v object_type	Implementing method's expected object type
+ * @v step		Implementing method
+ * @ret step		Process step method
+ */
+#define PROC_STEP( object_type, step )					      \
+	( ( ( ( typeof ( step ) * ) NULL ) ==				      \
+	    ( ( void ( * ) ( object_type *object ) ) NULL ) ) ?		      \
+	  ( void ( * ) ( void *object ) ) step :			      \
+	  ( void ( * ) ( void *object ) ) step )
+
+/**
+ * Calculate offset of process within containing object
+ *
+ * @v object_type	Containing object data type
+ * @v name		Process name (i.e. field within object data type)
+ * @ret offset		Offset of process within containing object
+ */
+#define process_offset( object_type, name )				      \
+	( ( ( ( typeof ( ( ( object_type * ) NULL )->name ) * ) NULL )	      \
+	    == ( ( struct process * ) NULL ) )			      	      \
+	  ? offsetof ( object_type, name )				      \
+	  : offsetof ( object_type, name ) )
+
+/**
+ * Define a process descriptor
+ *
+ * @v object_type	Containing object data type
+ * @v process		Process name (i.e. field within object data type)
+ * @v step		Process' step() method
+ * @ret desc		Object interface descriptor
+ */
+#define PROC_DESC( object_type, process, _step ) {			      \
+		.offset = process_offset ( object_type, process ),	      \
+		.step = PROC_STEP ( object_type, _step ),		      \
+	}
+
+/**
+ * Define a process descriptor for a pure process
+ *
+ * A pure process is a process that does not have a containing object.
+ *
+ * @v step		Process' step() method
+ * @ret desc		Object interface descriptor
+ */
+#define PROC_DESC_PURE( _step ) {					      \
+		.offset = 0,						      \
+		.step = PROC_STEP ( struct process, _step ),		      \
+	}
+
+extern void * __attribute__ (( pure ))
+process_object ( struct process *process );
 extern void process_add ( struct process *process );
 extern void process_del ( struct process *process );
 extern void step ( void );
@@ -41,14 +103,15 @@ extern void step ( void );
  * Initialise process without adding to process list
  *
  * @v process		Process
- * @v step		Process' step() method
+ * @v desc		Process descriptor
+ * @v refcnt		Containing object reference count, or NULL
  */
 static inline __attribute__ (( always_inline )) void
 process_init_stopped ( struct process *process,
-		       void ( * step ) ( struct process *process ),
+		       struct process_descriptor *desc,
 		       struct refcnt *refcnt ) {
 	INIT_LIST_HEAD ( &process->list );
-	process->step = step;
+	process->desc = desc;
 	process->refcnt = refcnt;
 }
 
@@ -56,13 +119,14 @@ process_init_stopped ( struct process *process,
  * Initialise process and add to process list
  *
  * @v process		Process
- * @v step		Process' step() method
+ * @v desc		Process descriptor
+ * @v refcnt		Containing object reference count, or NULL
  */
 static inline __attribute__ (( always_inline )) void
 process_init ( struct process *process,
-	       void ( * step ) ( struct process *process ),
+	       struct process_descriptor *desc,
 	       struct refcnt *refcnt ) {
-	process_init_stopped ( process, step, refcnt );
+	process_init_stopped ( process, desc, refcnt );
 	process_add ( process );
 }
 
@@ -88,4 +152,36 @@ process_running ( struct process *process ) {
  */
 #define __permanent_process __table_entry ( PERMANENT_PROCESSES, 01 )
 
+/** Define a permanent process
+ *
+ */
+#define PERMANENT_PROCESS( name, step )					      \
+struct process_descriptor name ## _desc = PROC_DESC_PURE ( step );	      \
+struct process name __permanent_process = {				      \
+	.list = LIST_HEAD_INIT ( name.list ),				      \
+	.desc = & name ## _desc,					      \
+	.refcnt = NULL,							      \
+};
+
+/**
+ * Find debugging colourisation for a process
+ *
+ * @v process		Process
+ * @ret col		Debugging colourisation
+ *
+ * Use as the first argument to DBGC() or equivalent macro.
+ */
+#define PROC_COL( process ) process_object ( process )
+
+/** printf() format string for PROC_DBG() */
+#define PROC_FMT "%p+%zx"
+
+/**
+ * printf() arguments for representing a process
+ *
+ * @v process		Process
+ * @ret args		printf() argument list corresponding to PROC_FMT
+ */
+#define PROC_DBG( process ) process_object ( process ), (process)->desc->offset
+
 #endif /* _IPXE_PROCESS_H */