[PATCH 2/5] introduce-resume-dependency.patch

[Andy Green]

Defines a way for drivers to defer execution of resume callbacks
until one or more other driver they are dependent on has itself
resumed.

Signed-off-by: Andy Green <andy at openmoko.com>
---

 include/linux/resume-dependency.h |   78 +++++++++++++++++++++++++++++++++++++
 1 files changed, 78 insertions(+), 0 deletions(-)
 create mode 100644 include/linux/resume-dependency.h

diff --git a/include/linux/resume-dependency.h b/include/linux/resume-dependency.h
new file mode 100644
index 0000000..b13aa3e
--- /dev/null
+++ b/include/linux/resume-dependency.h
@@ -0,0 +1,78 @@
+#ifndef __RESUME_DEPENDENCY_H__
+#define __RESUME_DEPENDENCY_H__
+
+/* Resume dependency framework
+ *
+ * (C) 2008 Openmoko, Inc.
+ * Author: Andy Green <andy at openmoko.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; version 2.1.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ *
+ */
+
+#include <linux/list.h>
+
+struct resume_dependency {
+	struct list_head list;
+
+	void (*callback)(void *); /* called with context as arg */
+	void * context;
+	int called_flag; /* set to 1 after called, use for multi dep */
+};
+
+/* if you are a driver accept to have other drivers as dependencies, you need to
+ * instantiate a struct resume_dependency above, then initialize it by invoking
+ * init_resume_dependency_list() on it
+ */
+
+#define init_resume_dependency_list(_head) \
+	INIT_LIST_HEAD(&_head.list);
+
+
+/* if your resume function depends on something else being resumed first, you
+ * can register the dependency by calling this in your suspend function with
+ * head being the list held by the thing you are dependent on, and dep being
+ * your struct resume_dependency
+ */
+
+#define register_resume_dependency(_head, _dep) { \
+	_dep->called_flag = 0; \
+	list_add(&_dep->list, &_head->list); \
+}
+
+/* In the resume function that things can be dependent on, at the end you
+ * invoke this macro.  This calls back the dependent resumes now it is safe to
+ * use the resumed thing they were dependent on.
+ */
+
+#define callback_all_resume_dependencies(_head) { \
+	struct list_head *_pos, *_q; \
+	struct resume_dependency *_dep; \
+\
+	list_for_each_safe(pos, _q, &_head.list) { \
+		_dep = list_entry(_pos, struct resume_dependency, list); \
+		_dep->called_flag = 1; \
+		(_dep->callback)(dep->context); \
+		list_del(_pos); \
+	} \
+}
+
+/* if your resume action is dependent on multiple drivers being resumed already,
+ * register the same callback with each driver you are dependent on, and check
+ * .called_flag for all of the struct resume_dependency.  When they are all 1
+ * you know it is the last callback and you can resume, otherwise just return
+ */
+
+#endif