[PATCH 04/14] init: deps: order network interfaces by link order

[Alexander Holler <holler@ahsoftware.de>]

In order to provide stable interface numbers, network interface drivers
will be ordered by the link order. This is easy to accomplish by adding
dependencies.

Assuming three different ethernet-drivers, without any special code,
the dependency graph would not require any special order inbetween them
and would look like that:

    eth-driver-base
   /      |       \
eth-x   eth-y    eth-z

Now we just add dependencies. With the additional dependencies the graph
looks like:

 eth-driver-base
  |     | |
eth-x   | |
  |     | |
eth-y  -| |
  |       |
eth-z  ---|

Signed-off-by: Alexander Holler <holler@ahsoftware.de>
---
 include/linux/driver_ids.h | 11 +++++++++++
 init/dependencies.c        |  9 +++++++++
 2 files changed, 20 insertions(+)

diff --git a/include/linux/driver_ids.h b/include/linux/driver_ids.h
index 60964fe..1133a68 100644
--- a/include/linux/driver_ids.h
+++ b/include/linux/driver_ids.h
@@ -15,6 +15,17 @@
 enum {
 	drvid_unused,
 	/* To be filled */
+
+	/*
+	 * Network drivers will be ordered according to the link order
+	 * (which means not necessarily according to their appearance
+	 * here).
+	 * This provides stable interface numbers.
+	 * Therefor their IDs have to be in the following block.
+	 */
+	drvid_network_drivers_start,
+	drvid_network_drivers_end,
+
 	drvid_max
 };
 
diff --git a/init/dependencies.c b/init/dependencies.c
index b484f67..027fc4b 100644
--- a/init/dependencies.c
+++ b/init/dependencies.c
@@ -301,12 +301,21 @@ static int __init add_dependencies(void)
 static void __init build_inventory(void)
 {
 	const struct _annotated_initcall *ac;
+	unsigned id_last_network_driver = 0;
 
 	ac = __annotated_initcall_start;
 	for (; ac < __annotated_initcall_end; ++ac) {
 		include_node[ac->id] = true;
 		annotated_initcall_by_drvid[ac->id] = ac;
 		nvertices = max(nvertices, ac->id);
+		/* order network drivers by link order*/
+		if (ac->id > drvid_network_drivers_start &&
+				ac->id < drvid_network_drivers_end) {
+			if (id_last_network_driver)
+				add_initcall_dependency(ac->id,
+					id_last_network_driver);
+			id_last_network_driver = ac->id;
+		}
 	}
 }
 
-- 
2.1.0