[PATCH v3 1/3] pmbus: core: add helpers for byte write and read modify write

[<atull@opensource.altera.com>]

From: Alan Tull <atull@opensource.altera.com>

Add two helper functions:
 * pmbus_write_byte_data  = paged byte write
 * pmbus_update_byte_data = paged byte read/modify/write

Signed-off-by: Alan Tull <atull@opensource.altera.com>
---
 drivers/hwmon/pmbus/pmbus_core.c |   31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index 291d11f..d6c3701 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -253,6 +253,37 @@ int pmbus_read_byte_data(struct i2c_client *client, int page, u8 reg)
 }
 EXPORT_SYMBOL_GPL(pmbus_read_byte_data);
 
+int pmbus_write_byte_data(struct i2c_client *client, int page, u8 reg, u8 value)
+{
+	int rv;
+
+	rv = pmbus_set_page(client, page);
+	if (rv < 0)
+		return rv;
+
+	return i2c_smbus_write_byte_data(client, reg, value);
+}
+EXPORT_SYMBOL_GPL(pmbus_write_byte_data);
+
+int pmbus_update_byte_data(struct i2c_client *client, int page, u8 reg,
+			   u8 mask, u8 value)
+{
+	unsigned int tmp;
+	int rv;
+
+	rv = pmbus_read_byte_data(client, page, reg);
+	if (rv < 0)
+		return rv;
+
+	tmp = (rv & ~mask) | (value & mask);
+
+	if (tmp != rv)
+		rv = pmbus_write_byte_data(client, page, reg, tmp);
+
+	return rv;
+}
+EXPORT_SYMBOL_GPL(pmbus_update_byte_data);
+
 /*
  * _pmbus_read_byte_data() is similar to pmbus_read_byte_data(), but checks if
  * a device specific mapping function exists and calls it if necessary.
-- 
1.7.9.5