[PATCH 2/4] regmap: implement regmap_init_i2c_smbus

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Some i2c devices need the SMBus accessors instead of the raw i2c access,
so provide a regmap helper for that.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 drivers/base/regmap/regmap-i2c.c | 37 ++++++++++++++++++++++++++++++++
 include/regmap.h                 |  3 +++
 2 files changed, 40 insertions(+)

diff --git a/drivers/base/regmap/regmap-i2c.c b/drivers/base/regmap/regmap-i2c.c
index 5e3705162c92..756bc224cc3b 100644
--- a/drivers/base/regmap/regmap-i2c.c
+++ b/drivers/base/regmap/regmap-i2c.c
@@ -42,3 +42,40 @@ struct regmap *regmap_init_i2c(struct i2c_client *client,
 {
 	return  regmap_init(&client->dev, &regmap_regmap_i2c_bus, client, config);
 }
+
+static int regmap_smbus_byte_reg_read(void *client, unsigned int reg, unsigned int *val)
+{
+	int ret;
+
+	if (reg > 0xff)
+		return -EINVAL;
+
+	ret = i2c_smbus_read_byte_data(client, reg);
+	if (ret < 0)
+		return ret;
+
+	*val = ret;
+
+	return 0;
+}
+
+static int regmap_smbus_byte_reg_write(void *client, unsigned int reg, unsigned int val)
+{
+	if (val > 0xff || reg > 0xff)
+		return -EINVAL;
+
+	return i2c_smbus_write_byte_data(client, reg, val);
+}
+
+static const struct regmap_bus regmap_smbus_byte = {
+	.reg_write = regmap_smbus_byte_reg_write,
+	.reg_read = regmap_smbus_byte_reg_read,
+};
+
+struct regmap *regmap_init_i2c_smbus(struct i2c_client *client,
+			       const struct regmap_config *config)
+{
+	if (config->val_bits != 8 || config->reg_bits != 8)
+		return ERR_PTR(-ENOSYS);
+	return regmap_init(&client->dev, &regmap_smbus_byte, client, config);
+}
diff --git a/include/regmap.h b/include/regmap.h
index 4b30c2177629..5bedb30d8a78 100644
--- a/include/regmap.h
+++ b/include/regmap.h
@@ -89,6 +89,9 @@ struct i2c_client;
 struct regmap *regmap_init_i2c(struct i2c_client *i2c,
 			       const struct regmap_config *config);
 
+struct regmap *regmap_init_i2c_smbus(struct i2c_client *client,
+			       const struct regmap_config *config);
+
 /**
  * regmap_init_mmio() - Initialise register map
  *
-- 
2.30.2