ACPI: battery: check for battery present on /proc/battery access

http://bugzilla.kernel.org/show_bug.cgi?id=7200

Signed-off-by: Vladimir Lebedev <vladimir.p.lebedev@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/battery.c

@@ -324,6 +324,13 @@ static int acpi_battery_check(struct acpi_battery *battery)
 	return result;
 }
 
+static void acpi_battery_check_present(struct acpi_battery *battery)
+{
+	if (!battery->flags.present) {
+		acpi_battery_check(battery);
+	}
+}
+
 /* --------------------------------------------------------------------------
                               FS Interface (/proc)
    -------------------------------------------------------------------------- */
@@ -340,6 +347,8 @@ static int acpi_battery_read_info(struct seq_file *seq, void *offset)
 	if (!battery)
 		goto end;
 
+	acpi_battery_check_present(battery);
+
 	if (battery->flags.present)
 		seq_printf(seq, "present:                 yes\n");
 	else {
@@ -424,6 +433,8 @@ static int acpi_battery_read_state(struct seq_file *seq, void *offset)
 	if (!battery)
 		goto end;
 
+	acpi_battery_check_present(battery);
+
 	if (battery->flags.present)
 		seq_printf(seq, "present:                 yes\n");
 	else {
@@ -499,6 +510,8 @@ static int acpi_battery_read_alarm(struct seq_file *seq, void *offset)
 	if (!battery)
 		goto end;
 
+	acpi_battery_check_present(battery);
+
 	if (!battery->flags.present) {
 		seq_printf(seq, "present:                 no\n");
 		goto end;
@@ -536,6 +549,8 @@ acpi_battery_write_alarm(struct file *file,
 	if (!battery || (count > sizeof(alarm_string) - 1))
 		return -EINVAL;
 
+	acpi_battery_check_present(battery);
+
 	if (!battery->flags.present)
 		return -ENODEV;