power_supply: add eeprom dump file to olpc_battery's sysfs

This allows you to dump 0x60 bytes from the battery's EEPROM (starting at
address 0x20).  Note that it does an EC command for each byte, so it's pretty
slow.  OTOH, if you want to grab just a single byte from somewhere in the
EEPROM, you can do something like:

dd bs=1 count=1 skip=16 if=/sys/class/power_supply/olpc-battery/eeprom | od -x

Userspace battery collection/logging information needs this.
Signed-off-by: Andres Salomon <dilinger@debian.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>

drivers/power/olpc_battery.c

@@ -274,6 +274,48 @@ static enum power_supply_property olpc_bat_props[] = {
 	POWER_SUPPLY_PROP_SERIAL_NUMBER,
 };
 
+/* EEPROM reading goes completely around the power_supply API, sadly */
+
+#define EEPROM_START	0x20
+#define EEPROM_END	0x80
+#define EEPROM_SIZE	(EEPROM_END - EEPROM_START)
+
+static ssize_t olpc_bat_eeprom_read(struct kobject *kobj,
+		struct bin_attribute *attr, char *buf, loff_t off, size_t count)
+{
+	uint8_t ec_byte;
+	int ret, end;
+
+	if (off >= EEPROM_SIZE)
+		return 0;
+	if (off + count > EEPROM_SIZE)
+		count = EEPROM_SIZE - off;
+
+	end = EEPROM_START + off + count;
+	for (ec_byte = EEPROM_START + off; ec_byte < end; ec_byte++) {
+		ret = olpc_ec_cmd(EC_BAT_EEPROM, &ec_byte, 1,
+				&buf[ec_byte - EEPROM_START], 1);
+		if (ret) {
+			printk(KERN_ERR "olpc-battery:  EC command "
+					"EC_BAT_EEPROM @ 0x%x failed -"
+					" %d!\n", ec_byte, ret);
+			return -EIO;
+		}
+	}
+
+	return count;
+}
+
+static struct bin_attribute olpc_bat_eeprom = {
+	.attr = {
+		.name = "eeprom",
+		.mode = S_IRUGO,
+		.owner = THIS_MODULE,
+	},
+	.size = 0,
+	.read = olpc_bat_eeprom_read,
+};
+
 /*********************************************************************
  *		Initialisation
  *********************************************************************/
@@ -327,8 +369,14 @@ static int __init olpc_bat_init(void)
 	if (ret)
 		goto battery_failed;
 
+	ret = device_create_bin_file(olpc_bat.dev, &olpc_bat_eeprom);
+	if (ret)
+		goto eeprom_failed;
+
 	goto success;
 
+eeprom_failed:
+	power_supply_unregister(&olpc_bat);
 battery_failed:
 	power_supply_unregister(&olpc_ac);
 ac_failed:
@@ -339,6 +387,7 @@ static int __init olpc_bat_init(void)
 
 static void __exit olpc_bat_exit(void)
 {
+	device_remove_bin_file(olpc_bat.dev, &olpc_bat_eeprom);
 	power_supply_unregister(&olpc_bat);
 	power_supply_unregister(&olpc_ac);
 	platform_device_unregister(bat_pdev);