crypto: atmel-sha204a - provide the otp content

Set up sysfs for the Atmel SHA204a. Provide the content of the otp zone as
an attribute field on the sysfs entry. Thereby make sure that if the chip
is locked, not connected or trouble with the i2c bus, the sysfs device is
not set up. This is mostly already handled in atmel-i2c.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/atmel-sha204a.c

@@ -114,6 +114,39 @@ static int atmel_sha204a_otp_read(struct i2c_client *client, u16 addr, u8 *otp)
 	return ret;
 }
 
+static ssize_t otp_show(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	u16 addr;
+	u8 otp[OTP_ZONE_SIZE];
+	char *str = buf;
+	struct i2c_client *client = to_i2c_client(dev);
+	int i;
+
+	for (addr = 0; addr < OTP_ZONE_SIZE/4; addr++) {
+		if (atmel_sha204a_otp_read(client, addr, otp + addr * 4) < 0) {
+			dev_err(dev, "failed to read otp zone\n");
+			break;
+		}
+	}
+
+	for (i = 0; i < addr*2; i++)
+		str += sprintf(str, "%02X", otp[i]);
+	str += sprintf(str, "\n");
+	return str - buf;
+}
+static DEVICE_ATTR_RO(otp);
+
+static struct attribute *atmel_sha204a_attrs[] = {
+	&dev_attr_otp.attr,
+	NULL
+};
+
+static const struct attribute_group atmel_sha204a_groups = {
+	.name = "atsha204a",
+	.attrs = atmel_sha204a_attrs,
+};
+
 static int atmel_sha204a_probe(struct i2c_client *client)
 {
 	struct atmel_i2c_client_priv *i2c_priv;
@@ -134,6 +167,16 @@ static int atmel_sha204a_probe(struct i2c_client *client)
 	if (ret)
 		dev_warn(&client->dev, "failed to register RNG (%d)\n", ret);
 
+	/* otp read out */
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -ENODEV;
+
+	ret = sysfs_create_group(&client->dev.kobj, &atmel_sha204a_groups);
+	if (ret) {
+		dev_err(&client->dev, "failed to register sysfs entry\n");
+		return ret;
+	}
+
 	return ret;
 }
 
@@ -146,6 +189,8 @@ static void atmel_sha204a_remove(struct i2c_client *client)
 		return;
 	}
 
+	sysfs_remove_group(&client->dev.kobj, &atmel_sha204a_groups);
+
 	kfree((void *)i2c_priv->hwrng.priv);
 }