gpiolib: annotate gpio-intialization with __must_check

Because GPIOs can have crucial functions especially in embedded systems,
we are better safe than sorry regarding their configuration.  For
gpio_request, the documentation is simply enforced: <quote>"The return
value of gpio_request() must be checked."</quote> For gpio_direction_* and
gpio_request_*, we now act accordingly.

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Cc: Greg KH <gregkh@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index ff5c660..6098cae 100644
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -147,11 +147,11 @@
 /* Always use the library code for GPIO management calls,
  * or when sleeping may be involved.
  */
-extern int gpio_request(unsigned gpio, const char *label);
+extern int __must_check gpio_request(unsigned gpio, const char *label);
 extern void gpio_free(unsigned gpio);
 
-extern int gpio_direction_input(unsigned gpio);
-extern int gpio_direction_output(unsigned gpio, int value);
+extern int __must_check gpio_direction_input(unsigned gpio);
+extern int __must_check gpio_direction_output(unsigned gpio, int value);
 
 extern int gpio_set_debounce(unsigned gpio, unsigned debounce);
 
@@ -192,8 +192,8 @@
 	const char	*label;
 };
 
-extern int gpio_request_one(unsigned gpio, unsigned long flags, const char *label);
-extern int gpio_request_array(struct gpio *array, size_t num);
+extern int __must_check gpio_request_one(unsigned gpio, unsigned long flags, const char *label);
+extern int __must_check gpio_request_array(struct gpio *array, size_t num);
 extern void gpio_free_array(struct gpio *array, size_t num);
 
 #ifdef CONFIG_GPIO_SYSFS