i2c: Guard against oopses from bad init sequences

Guard I2C against oopsing because of init sequence problems, by
verifying that i2c_init() has been called before calling any
routines that rely on that initialization.  This specific test
just requires that bus_register(&i2c_bus_type) was called.

Examples of this kind of oopsing come from subystems and drivers
which register I2C drivers in their subsys_initcall code but
which are statically linked before I2C by drivers/Makefile.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index b346a687ab59..a96e1bf27649 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -437,6 +437,10 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
 {
         int res = 0, dummy;
 
+        /* Can't register until after driver model init */
+        if (unlikely(WARN_ON(!i2c_bus_type.p)))
+                return -EAGAIN;
+
         mutex_init(&adap->bus_lock);
         mutex_init(&adap->clist_lock);
         INIT_LIST_HEAD(&adap->clients);
@@ -696,6 +700,10 @@ int i2c_register_driver(struct module *owner, struct i2c_driver *driver)
 {
         int res;
 
+        /* Can't register until after driver model init */
+        if (unlikely(WARN_ON(!i2c_bus_type.p)))
+                return -EAGAIN;
+
         /* new style driver methods can't mix with legacy ones */
         if (is_newstyle_driver(driver)) {
                 if (driver->attach_adapter || driver->detach_adapter