ATTR{}== always fails if the attribute does not exist

TODO

@@ -1,3 +1,4 @@
+
   o add DVB variables to kernel (patch sent), and drop shell script rule
   o DEVTYPE for disks is set by the kernel, they will be removed from
     the default rules

udev/udev-rules.c

@@ -1808,11 +1808,10 @@ static int match_attr(struct udev_rules *rules, struct udev_device *dev, struct
 		const char *val;
 
 		val = udev_device_get_sysattr_value(dev, key_name);
-		if (val != NULL)
-			util_strlcpy(value, val, sizeof(value));
+		if (val == NULL)
+			return -1;
+		util_strlcpy(value, val, sizeof(value));
 	}
-	if (value[0] == '\0')
-		return -1;
 
 	/* strip trailing whitespace of value, if not asked to match for it */
 	len = strlen(key_value);

udev/udev.xml

@@ -186,8 +186,7 @@
               <listitem>
                 <para>Match sysfs attribute values of the event device. Trailing
                 whitespace in the attribute values is ignored, if the specified match
-                value does not contain trailing whitespace itself. Depending on the type
-                of operator, this key is also used to set the value of a sysfs attribute.
+                value does not contain trailing whitespace itself.
                 </para>
               </listitem>
             </varlistentry>
@@ -318,8 +317,7 @@
               <term><option>ATTR{<replaceable>key</replaceable>}</option></term>
               <listitem>
                 <para>The value that should be written to a sysfs attribute of the
-                event device. Depending on the type of operator, this key is also
-                used to match against the value of a sysfs attribute.</para>
+                event device.</para>
               </listitem>
             </varlistentry>