[PATCH 1/3] hwmon: (pmbus) add support for QUERY command

[Kallas, Pawel]

QUERY command is used for checking if given command is supported by
the device and what data format it uses. It is needed to check if
READ_EIN and READ_EOUT commands are supported.

Signed-off-by: Kallas, Pawel <pawel.kallas@xxxxxxxxx>
---
 Documentation/hwmon/pmbus-core.rst |  7 +++++++
 drivers/hwmon/pmbus/pmbus.h        | 14 ++++++++++++++
 drivers/hwmon/pmbus/pmbus_core.c   | 21 +++++++++++++++++++++
 3 files changed, 42 insertions(+)

diff --git a/Documentation/hwmon/pmbus-core.rst b/Documentation/hwmon/pmbus-core.rst
index e7e0c9ef10bec..6ba0a9d86f1f6 100644
--- a/Documentation/hwmon/pmbus-core.rst
+++ b/Documentation/hwmon/pmbus-core.rst
@@ -268,6 +268,13 @@ otherwise.
 This function calls the device specific write_byte function if defined to
 obtain the chip status. Therefore, it must _not_ be called from that function.
 
+::
+
+  int pmbus_query_register(struct i2c_client *client, int reg);
+
+Send pmbus QUERY command for specific register. Returns QUERY command
+response or negative value on fail.
+
 ::
 
   int pmbus_do_probe(struct i2c_client *client, struct pmbus_driver_info *info);
diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
index 75aa97b1ecc05..971554f40dba6 100644
--- a/drivers/hwmon/pmbus/pmbus.h
+++ b/drivers/hwmon/pmbus/pmbus.h
@@ -364,6 +364,19 @@ enum pmbus_fan_mode { percent = 0, rpm };
 #define PB_CML_FAULT_INVALID_DATA	BIT(6)
 #define PB_CML_FAULT_INVALID_COMMAND	BIT(7)
 
+/*
+ * QUERY
+ */
+#define PB_QUERY_COMMAND_MODE_MASK	0x1C
+
+#define PB_QUERY_COMMAND_MODE_LINEAR	0x00
+#define PB_QUERY_COMMAND_MODE_DIRECT	0x0C
+#define PB_QUERY_COMMAND_MODE_VID	0x14
+
+#define PB_QUERY_COMMAND_SUPPORTED_FOR_READ	BIT(5)
+#define PB_QUERY_COMMAND_SUPPORTED_FOR_WRITE	BIT(6)
+#define PB_QUERY_COMMAND_SUPPORTED	BIT(7)
+
 enum pmbus_sensor_classes {
 	PSC_VOLTAGE_IN = 0,
 	PSC_VOLTAGE_OUT,
@@ -492,6 +505,7 @@ int pmbus_update_byte_data(struct i2c_client *client, int page, u8 reg,
 void pmbus_clear_faults(struct i2c_client *client);
 bool pmbus_check_byte_register(struct i2c_client *client, int page, int reg);
 bool pmbus_check_word_register(struct i2c_client *client, int page, int reg);
+int pmbus_query_register(struct i2c_client *client, int reg);
 int pmbus_do_probe(struct i2c_client *client, struct pmbus_driver_info *info);
 const struct pmbus_driver_info *pmbus_get_driver_info(struct i2c_client
 						      *client);
diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index d462f732f3b40..4bcb70ab9b598 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -648,6 +648,27 @@ static int pmbus_get_status(struct i2c_client *client, int page, int reg)
 	return status;
 }
 
+int pmbus_query_register(struct i2c_client *client, int reg)
+{
+	int rv;
+	union i2c_smbus_data data;
+
+	data.block[0] = 1;
+	data.block[1] = reg;
+
+	rv = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+			    I2C_SMBUS_WRITE, PMBUS_QUERY,
+			    I2C_SMBUS_BLOCK_PROC_CALL, &data);
+	if (rv < 0)
+		return rv;
+
+	if (data.block[0] != 1)
+		return -EIO;
+
+	return data.block[1];
+}
+EXPORT_SYMBOL_NS_GPL(pmbus_query_register, PMBUS);
+
 static void pmbus_update_sensor_data(struct i2c_client *client, struct pmbus_sensor *sensor)
 {
 	if (sensor->data < 0 || sensor->update)