[ALSA] oxygen: add I2C support

Add a function to write I2C registers.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/pci/oxygen/oxygen_io.c b/sound/pci/oxygen/oxygen_io.c
index 74e23ef..5569606 100644
--- a/sound/pci/oxygen/oxygen_io.c
+++ b/sound/pci/oxygen/oxygen_io.c
@@ -190,12 +190,31 @@
 		--count;
 	}
 
-	spin_lock_irq(&chip->reg_lock);
 	oxygen_write8(chip, OXYGEN_SPI_DATA1, data);
 	oxygen_write8(chip, OXYGEN_SPI_DATA2, data >> 8);
 	if (control & OXYGEN_SPI_DATA_LENGTH_3)
 		oxygen_write8(chip, OXYGEN_SPI_DATA3, data >> 16);
 	oxygen_write8(chip, OXYGEN_SPI_CONTROL, control);
-	spin_unlock_irq(&chip->reg_lock);
 }
 EXPORT_SYMBOL(oxygen_write_spi);
+
+void oxygen_write_i2c(struct oxygen *chip, u8 device, u8 map, u8 data)
+{
+	unsigned long timeout;
+
+	/* should not need more than about 300 us */
+	timeout = jiffies + msecs_to_jiffies(1);
+	do {
+		if (!(oxygen_read16(chip, OXYGEN_2WIRE_BUS_STATUS)
+		      & OXYGEN_2WIRE_BUSY))
+			break;
+		udelay(1);
+		cond_resched();
+	} while (time_after_eq(timeout, jiffies));
+
+	oxygen_write8(chip, OXYGEN_2WIRE_MAP, map);
+	oxygen_write8(chip, OXYGEN_2WIRE_DATA, data);
+	oxygen_write8(chip, OXYGEN_2WIRE_CONTROL,
+		      device | OXYGEN_2WIRE_DIR_WRITE);
+}
+EXPORT_SYMBOL(oxygen_write_i2c);