[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 <anemo@mba.ocn.ne.jp>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 11 insertions, 6 deletions

diff --git a/drivers/rtc/rtc-dev.c b/drivers/rtc/rtc-dev.c
index b1e3e6179e56..6c9ad92747fd 100644
--- a/drivers/rtc/rtc-dev.c
+++ b/drivers/rtc/rtc-dev.c
@@ -58,7 +58,7 @@ rtc_dev_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
         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);
@@ -90,11 +90,16 @@ rtc_dev_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
         if (ret == 0) {
                 /* Check for any data updates */
                 if (rtc->ops->read_callback)
-                        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);
+                        data = rtc->ops->read_callback(rtc->class_dev.dev,
+                                                       data);
+
+                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;
 }