regmap-i2c: Add smbus i2c block support

This allows to read/write up to 32 bytes of data and is to be prefered
if supported before the register read/write smbus support.
Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/base/regmap/regmap-i2c.c

@@ -209,11 +209,60 @@ static struct regmap_bus regmap_i2c = {
 	.val_format_endian_default = REGMAP_ENDIAN_BIG,
 };
 
+static int regmap_i2c_smbus_i2c_write(void *context, const void *data,
+				      size_t count)
+{
+	struct device *dev = context;
+	struct i2c_client *i2c = to_i2c_client(dev);
+
+	if (count < 1)
+		return -EINVAL;
+	if (count >= I2C_SMBUS_BLOCK_MAX)
+		return -E2BIG;
+
+	--count;
+	return i2c_smbus_write_i2c_block_data(i2c, ((u8 *)data)[0], count,
+					      ((u8 *)data + 1));
+}
+
+static int regmap_i2c_smbus_i2c_read(void *context, const void *reg,
+				     size_t reg_size, void *val,
+				     size_t val_size)
+{
+	struct device *dev = context;
+	struct i2c_client *i2c = to_i2c_client(dev);
+	int ret;
+
+	if (reg_size != 1 || val_size < 1)
+		return -EINVAL;
+	if (val_size >= I2C_SMBUS_BLOCK_MAX)
+		return -E2BIG;
+
+	ret = i2c_smbus_read_i2c_block_data(i2c, ((u8 *)reg)[0], val_size, val);
+	if (ret == val_size)
+		return 0;
+	else if (ret < 0)
+		return ret;
+	else
+		return -EIO;
+}
+
+static struct regmap_bus regmap_i2c_smbus_i2c_block = {
+	.write = regmap_i2c_smbus_i2c_write,
+	.read = regmap_i2c_smbus_i2c_read,
+	.max_raw_read = I2C_SMBUS_BLOCK_MAX,
+	.max_raw_write = I2C_SMBUS_BLOCK_MAX,
+};
+
 static const struct regmap_bus *regmap_get_i2c_bus(struct i2c_client *i2c,
 					const struct regmap_config *config)
 {
 	if (i2c_check_functionality(i2c->adapter, I2C_FUNC_I2C))
 		return &regmap_i2c;
+	else if (config->reg_bits == 8 &&
+		 i2c_check_functionality(i2c->adapter,
+					 I2C_FUNC_SMBUS_I2C_BLOCK))
+		return &regmap_i2c_smbus_i2c_block;
 	else if (config->val_bits == 16 && config->reg_bits == 8 &&
 		 i2c_check_functionality(i2c->adapter,
 					 I2C_FUNC_SMBUS_WORD_DATA))