Hi,

On Tue, Jan 07, 2014 at 11:08:03AM +0800, Duson Lin wrote:

+/*
+ ******************************************************************
+ * General functions
+ ******************************************************************
+ */
+/*
+ * (value from firmware) * 10 + 790 = dpi
+ * we also have to convert dpi to dots/mm (*10/254 to avoid floating point)
+ */
+static unsigned int elan_convert_res(char val)
+{
+	int res;
+	if (val & 0x80) {
+		val = ~val + 1;
+		res = (790 - val * 10) * 10 / 254;
+	} else
+		res = (val * 10 + 790) * 10 / 254;
+	return res;
+}

Why isn't this simply:

	res = ((int)val * 10 + 790) * 10 / 254;

?

If high bit is 1 you basically do the 2 complement by hand to get to
positive and then subtract. Which shoudl be the same as adding positive
value.

Thanks.

-- 
Dmitry