led_class: storing a value can act but return -EINVAL

[Johannes Berg <johannes@sipsolutions.net>]

When I store something into the brightness sysfs attribute of an LED, it
will accept the value but return -EINVAL:

johannes:/sys/class/leds/pmu-front-led# echo 255 > brightness
bash: echo: write error: Invalid argument

(yet the LED turns on)

This happens because the store callback doesn't consume all the input.

There are two possible ways to handle this:
a) accept anything that begins with a valid number.
b) reject anything that isn't *only* a number

The following patch implements a), for b) you'd have to make the if
statement have ' && after-buf == size' instead of this patch.

I don't know which approach is generally preferred, but acting and then
returning an error value doesn't seem nice.
Maybe b) should be implemented instead to stop people from storing
things like '0 hahaha stupid kernel ignores this' into the attribute :)

johannes

--- linux-2.6.orig/drivers/leds/led-class.c	2006-04-29 13:23:49.013288994 +0200
+++ linux-2.6/drivers/leds/led-class.c	2006-04-29 13:28:14.183288994 +0200
@@ -45,7 +45,7 @@ static ssize_t led_brightness_store(stru
 	unsigned long state = simple_strtoul(buf, &after, 10);
 
 	if (after - buf > 0) {
-		ret = after - buf;
+		ret = size;
 		led_set_brightness(led_cdev, state);
 	}