dm: i2c: dts: Support an offset-len device tree property
Since U-Boot can support different offset lengths (0-4 bytes), add a device
tree property to specify this. This avoids hard-coding it in the driver.
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/device-tree-bindings/i2c/i2c.txt b/doc/device-tree-bindings/i2c/i2c.txt
new file mode 100644
index 0000000..ea918dd
--- /dev/null
+++ b/doc/device-tree-bindings/i2c/i2c.txt
@@ -0,0 +1,28 @@
+U-Boot I2C
+----------
+
+U-Boot's I2C model has the concept of an offset within a chip (I2C target
+device). The offset can be up to 4 bytes long, but is normally 1 byte,
+meaning that offsets from 0 to 255 are supported by the chip. This often
+corresponds to register numbers.
+
+Apart from the controller-specific I2C bindings, U-Boot supports a special
+property which allows the chip offset length to be selected.
+
+Optional properties:
+- u-boot,i2c-offset-len - length of chip offset in bytes. If omitted the
+ default value of 1 is used.
+
+
+Example
+-------
+
+i2c4: i2c@12ca0000 {
+ cros-ec@1e {
+ reg = <0x1e>;
+ compatible = "google,cros-ec";
+ i2c-max-frequency = <100000>;
+ u-boot,i2c-offset-len = <0>;
+ ec-interrupt = <&gpx1 6 GPIO_ACTIVE_LOW>;
+ };
+};