soundwire: bus: add sdw_slave_get_current_bank helper

There has been 2 instances of this helper in codec drivers,
it does not make sense to keep duplicating this part of code.

Lets add a helper sdw_get_current_bank() for codec drivers to use it.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@oss.qualcomm.com>
Acked-by: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://patch.msgid.link/20250909121954.225833-5-srinivas.kandagatla@oss.qualcomm.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: Srinivas Kandagatla

drivers/soundwire/bus.c

@@ -1360,6 +1360,18 @@ int sdw_slave_get_scale_index(struct sdw_slave *slave, u8 *base)
 }
 EXPORT_SYMBOL(sdw_slave_get_scale_index);
 
+int sdw_slave_get_current_bank(struct sdw_slave *slave)
+{
+	int tmp;
+
+	tmp = sdw_read(slave, SDW_SCP_CTRL);
+	if (tmp < 0)
+		return tmp;
+
+	return FIELD_GET(SDW_SCP_STAT_CURR_BANK, tmp);
+}
+EXPORT_SYMBOL_GPL(sdw_slave_get_current_bank);
+
 static int sdw_slave_set_frequency(struct sdw_slave *slave)
 {
 	int scale_index;

include/linux/soundwire/sdw.h

@@ -1089,6 +1089,8 @@ int sdw_stream_remove_slave(struct sdw_slave *slave,
 
 struct device *of_sdw_find_device_by_node(struct device_node *np);
 
+int sdw_slave_get_current_bank(struct sdw_slave *sdev);
+
 int sdw_slave_get_scale_index(struct sdw_slave *slave, u8 *base);
 
 /* messaging and data APIs */
@@ -1128,6 +1130,12 @@ static inline struct device *of_sdw_find_device_by_node(struct device_node *np)
 	return NULL;
 }
 
+static inline int sdw_slave_get_current_bank(struct sdw_slave *sdev)
+{
+	WARN_ONCE(1, "SoundWire API is disabled");
+	return -EINVAL;
+}
+
 /* messaging and data APIs */
 static inline int sdw_read(struct sdw_slave *slave, u32 addr)
 {