soundwire: Add IO transfer

SoundWire bus supports read or write register(s) for SoundWire Slave
device. sdw_read() and sdw_write() APIs are provided for single
register read/write. sdw_nread() and sdw_nwrite() for operations on
contiguous registers.

Signed-off-by: Sanyog Kale <sanyog.r.kale@intel.com>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Acked-By: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/soundwire/bus.h b/drivers/soundwire/bus.h
index a549218..48eb7de 100644
--- a/drivers/soundwire/bus.h
+++ b/drivers/soundwire/bus.h
@@ -16,4 +16,40 @@ static inline int sdw_acpi_find_slaves(struct sdw_bus *bus)
 void sdw_extract_slave_id(struct sdw_bus *bus,
 			u64 addr, struct sdw_slave_id *id);
 
+enum {
+	SDW_MSG_FLAG_READ = 0,
+	SDW_MSG_FLAG_WRITE,
+};
+
+/**
+ * struct sdw_msg - Message structure
+ * @addr: Register address accessed in the Slave
+ * @len: number of messages
+ * @dev_num: Slave device number
+ * @addr_page1: SCP address page 1 Slave register
+ * @addr_page2: SCP address page 2 Slave register
+ * @flags: transfer flags, indicate if xfer is read or write
+ * @buf: message data buffer
+ * @ssp_sync: Send message at SSP (Stream Synchronization Point)
+ * @page: address requires paging
+ */
+struct sdw_msg {
+	u16 addr;
+	u16 len;
+	u8 dev_num;
+	u8 addr_page1;
+	u8 addr_page2;
+	u8 flags;
+	u8 *buf;
+	bool ssp_sync;
+	bool page;
+};
+
+int sdw_transfer(struct sdw_bus *bus, struct sdw_msg *msg);
+int sdw_transfer_defer(struct sdw_bus *bus, struct sdw_msg *msg,
+				struct sdw_defer *defer);
+
+int sdw_fill_msg(struct sdw_msg *msg, struct sdw_slave *slave,
+		u32 addr, size_t count, u16 dev_num, u8 flags, u8 *buf);
+
 #endif /* __SDW_BUS_H */