dm: i2c: Add I2C emulation driver for sandbox

In order to test I2C we need some sort of emulation interface. Add hooks
to allow a driver to emulate an I2C device for sandbox.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Heiko Schocher <hs@denx.de>
Reviewed-by: Masahiro Yamada <yamada.m@jp.panasonic.com>

drivers/i2c/Makefile

@@ -27,6 +27,7 @@ obj-$(CONFIG_SYS_I2C_OMAP34XX) += omap24xx_i2c.o
 obj-$(CONFIG_SYS_I2C_PPC4XX) += ppc4xx_i2c.o
 obj-$(CONFIG_SYS_I2C_RCAR) += rcar_i2c.o
 obj-$(CONFIG_SYS_I2C_S3C24X0) += s3c24x0_i2c.o
+obj-$(CONFIG_SYS_I2C_SANDBOX) += i2c-emul-uclass.o
 obj-$(CONFIG_SYS_I2C_SH) += sh_i2c.o
 obj-$(CONFIG_SYS_I2C_SOFT) += soft_i2c.o
 obj-$(CONFIG_SYS_I2C_TEGRA) += tegra_i2c.o

drivers/i2c/i2c-emul-uclass.c

@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2014 Google, Inc
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <i2c.h>
+
+UCLASS_DRIVER(i2c_emul) = {
+	.id		= UCLASS_I2C_EMUL,
+	.name		= "i2c_emul",
+};

include/dm/uclass-id.h

@@ -19,6 +19,7 @@ enum uclass_id {
 	UCLASS_TEST_FDT,
 	UCLASS_TEST_BUS,
 	UCLASS_SPI_EMUL,	/* sandbox SPI device emulator */
+	UCLASS_I2C_EMUL,	/* sandbox I2C device emulator */
 	UCLASS_SIMPLE_BUS,
 
 	/* U-Boot uclasses start here */