[PATCH] RTC: rtc-dev tweak for 64-bit kernel

Make rtc-dev work well on 64-bit platforms with 32-bit userland. On those
platforms, users might try to read 32-bit integer value. This patch make
rtc-dev's read() work well for both "int" and "long" size. This tweak is came
from genrtc driver.

Signed-off-by: Atsushi Nemoto <[e-mail]>
Cc: Alessandro Zummo <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/rtc/rtc-dev.c

···
 	unsigned long data;
 	ssize_t ret;
 
-	if (count < sizeof(unsigned long))
+	if (count != sizeof(unsigned int) && count < sizeof(unsigned long))
 		return -EINVAL;
 
 	add_wait_queue(&rtc->irq_queue, &wait);
···
 	if (ret == 0) {
 		/* Check for any data updates */
 		if (rtc->ops->read_callback)
-			data = rtc->ops->read_callback(rtc->class_dev.dev, data);
+			data = rtc->ops->read_callback(rtc->class_dev.dev,
+						       data);
 
-		ret = put_user(data, (unsigned long __user *)buf);
-		if (ret == 0)
-			ret = sizeof(unsigned long);
+		if (sizeof(int) != sizeof(long) &&
+		    count == sizeof(unsigned int))
+			ret = put_user(data, (unsigned int __user *)buf) ?:
+				sizeof(unsigned int);
+		else
+			ret = put_user(data, (unsigned long __user *)buf) ?:
+				sizeof(unsigned long);
 	}
 	return ret;
 }