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

[Atsushi Nemoto]

On Fri, 28 Apr 2006 23:31:52 -0700, Andrew Morton <akpm@xxxxxxxx> wrote:
> > Make rtc-dev more friendly to 64-bit platforms with 32-bit userland.
> > This tweak is came from genrtc driver.
> 
> Please define "friendly".  It's not clear what this patch does...
...
> 
> We normally omit the space between "sizeof" and "(".

Thanks for your comments.  Here is an updated patch.


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@xxxxxxxxxxxxx>

diff --git a/drivers/rtc/rtc-dev.c b/drivers/rtc/rtc-dev.c
index b1e3e61..6c9ad92 100644
--- a/drivers/rtc/rtc-dev.c
+++ b/drivers/rtc/rtc-dev.c
@@ -58,7 +58,7 @@ rtc_dev_read(struct file *file, char __u
 	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 __u
 	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;
 }
-
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