[PATCH] rtc-isl1208: Use SMBus functions if I2C isn't available

[Ben Gardner <gardner.ben-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

The rtc-isl1208 driver currently depends on raw I2C functionality.
This patch adds a fall-back to SMBus functions so that the driver can be 
used on a SMBus-only platforms, such as i2c-isch.

Signed-off-by: Ben Gardner <gardner.ben-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 drivers/rtc/rtc-isl1208.c |   68 +++++++++++++++++++++++++++++++-------------
 1 files changed, 48 insertions(+), 20 deletions(-)

diff --git a/drivers/rtc/rtc-isl1208.c b/drivers/rtc/rtc-isl1208.c
index ea10736..c553c7b 100644
--- a/drivers/rtc/rtc-isl1208.c
+++ b/drivers/rtc/rtc-isl1208.c
@@ -66,20 +66,35 @@ static int
 isl1208_i2c_read_regs(struct i2c_client *client, u8 reg, u8 buf[],
 		      unsigned len)
 {
-	u8 reg_addr[1] = { reg };
-	struct i2c_msg msgs[2] = {
-		{client->addr, 0, sizeof(reg_addr), reg_addr}
-		,
-		{client->addr, I2C_M_RD, len, buf}
-	};
 	int ret;
 
 	BUG_ON(reg > ISL1208_REG_USR2);
 	BUG_ON(reg + len > ISL1208_REG_USR2 + 1);
 
-	ret = i2c_transfer(client->adapter, msgs, 2);
-	if (ret > 0)
-		ret = 0;
+	if (i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
+		u8 reg_addr[1] = { reg };
+		struct i2c_msg msgs[2] = {
+			{client->addr, 0, sizeof(reg_addr), reg_addr}
+			,
+			{client->addr, I2C_M_RD, len, buf}
+		};
+
+		ret = i2c_transfer(client->adapter, msgs, 2);
+		if (ret > 0)
+			ret = 0;
+	} else {
+		int idx;
+		ret = i2c_smbus_read_byte_data(client, reg);
+		if (ret < 0)
+			return ret;
+		buf[0] = ret;
+		for (idx = 1; idx < len; idx++) {
+			ret = i2c_smbus_read_byte(client);
+			if (ret < 0)
+				return ret;
+			buf[idx] = ret;
+		}
+	}
 	return ret;
 }
 
@@ -88,21 +103,32 @@ static int
 isl1208_i2c_set_regs(struct i2c_client *client, u8 reg, u8 const buf[],
 		     unsigned len)
 {
-	u8 i2c_buf[ISL1208_REG_USR2 + 2];
-	struct i2c_msg msgs[1] = {
-		{client->addr, 0, len + 1, i2c_buf}
-	};
-	int ret;
+	int ret = 0;
 
 	BUG_ON(reg > ISL1208_REG_USR2);
 	BUG_ON(reg + len > ISL1208_REG_USR2 + 1);
 
-	i2c_buf[0] = reg;
-	memcpy(&i2c_buf[1], &buf[0], len);
+	if (i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
+		u8 i2c_buf[ISL1208_REG_USR2 + 2];
+		struct i2c_msg msgs[1] = {
+			{client->addr, 0, len + 1, i2c_buf}
+		};
+
+		i2c_buf[0] = reg;
+		memcpy(&i2c_buf[1], &buf[0], len);
 
-	ret = i2c_transfer(client->adapter, msgs, 1);
-	if (ret > 0)
-		ret = 0;
+		ret = i2c_transfer(client->adapter, msgs, 1);
+		if (ret > 0)
+			ret = 0;
+	} else {
+		int idx;
+		for (idx = 0; idx < len; idx++) {
+			ret = i2c_smbus_write_byte_data(client, reg + idx,
+							buf[idx]);
+			if (ret < 0)
+				return ret;
+		}
+	}
 	return ret;
 }
 
@@ -622,7 +648,9 @@ isl1208_probe(struct i2c_client *client, const struct i2c_device_id *id)
 	int rc = 0;
 	struct rtc_device *rtc;
 
-	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C) &&
+	    !i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE |
+				     I2C_FUNC_SMBUS_BYTE_DATA))
 		return -ENODEV;
 
 	if (isl1208_i2c_validate_client(client) < 0)
-- 
1.7.7