gpio: i2c expanders use subsys_init

From: David Brownell <[email protected]>

Make the I2C external GPIO expander drivers register themselves at subsys_initcall() time when they're statically linked.

SOC-integrated GPIOs are available starting very early -- early in arch_initcall() at latest, but often even before initcalls start to run -- so this improves consistency, so more subsystems can rely on GPIOs in their own subsys_initcall() code.

(This isn't a theoretical problem. This is one of several patches needed to resolve oopsing observed when statically linking kernels on a DaVinci EVM. Its pcf857x GPIOs needed to be available well before some other drivers initialized.)

This depends on a patch moving I2C's driver model init earlier in the boot sequence; otherwise this change would cause oopsing.

---
For the 2.6.28-rc0 merge window. Jean, can you include this in your I2C tree, so it only merges after the I2C init patch on which it depends? We want "git bisect" to work. ;)

 drivers/gpio/max732x.c |    5 ++++-
 drivers/gpio/pca953x.c |    5 ++++-
 drivers/gpio/pcf857x.c |    5 ++++-
 3 files changed, 12 insertions(+), 3 deletions(-)

@@ -372,7 +372,10 @@ static int __init max732x_init(void)
 {
 	return i2c_add_driver(&max732x_driver);
 }
-module_init(max732x_init);
+/* register after i2c postcore initcall and before
+ * subsys initcalls that may rely on these GPIOs
+ */
+subsys_initcall(max732x_init);
 
 static void __exit max732x_exit(void)
 {

@@ -289,7 +289,10 @@ static int __init pca953x_init(void)
 {
 	return i2c_add_driver(&pca953x_driver);
 }
-module_init(pca953x_init);
+/* register after i2c postcore initcall and before
+ * subsys initcalls that may rely on these GPIOs
+ */
+subsys_initcall(pca953x_init);
 
 static void __exit pca953x_exit(void)
 {

@@ -351,7 +351,10 @@ static int __init pcf857x_init(void)
 {
 	return i2c_add_driver(&pcf857x_driver);
 }
-module_init(pcf857x_init);
+/* register after i2c postcore initcall and before
+ * subsys initcalls that may rely on these GPIOs
+ */
+subsys_initcall(pcf857x_init);
 
 static void __exit pcf857x_exit(void)
 {