From: mstsxfx@gmail.com
Subject: [PATCH] use charge_now when energy_now is not present

Some batteries (like one in the Futjitsu Siemens Lifebook S71110) don't
export energy_now attribute and exports only change_now in the power_supply
sys directory. 
However, we can use this value when it is multiplied by current voltage.

Signed-off-by: Michal Hocko <mstsxfx@gmail.com>

--- a/powertop.c	2008-07-21 10:35:10.000000000 -0600
+++ b/powertop.c	2008-07-21 10:36:03.000000000 -0600
@@ -630,11 +630,19 @@ void print_battery_sysfs(void)
 
 		sprintf(filename, "/sys/class/power_supply/%s/energy_now", dirent->d_name);
 		file = fopen(filename, "r");
-		if (!file)
-			continue;
+		watts_left = 1;
+		if (!file) {
+			sprintf(filename, "/sys/class/power_supply/%s/charge_now", dirent->d_name);
+			file = fopen(filename, "r");
+			if (!file)
+				continue;
+
+			/* W = A * V */
+			watts_left = voltage;
+		}
 		memset(line, 0, 1024);
 		if (fgets(line, 1024, file) != NULL) {
-			watts_left = strtoull(line, NULL, 10) / 1000000.0;
+			watts_left *= strtoull(line, NULL, 10) / 1000000.0;
 		}
 		fclose(file);