i2c: Set default I2C bus number

This patch allows using i2c commands (e.g. "i2c probe", "i2c md", etc)
without the need to first select the bus number with e.g. "i2c dev 0".

This is the "i2c" command behavior similar to the one from pre DM, where
by default bus 0 was immediately accessible.

Signed-off-by: Lukasz Majewski <lukma@denx.de>

cmd/i2c.c

@@ -151,6 +151,16 @@ static int cmd_i2c_set_bus_num(unsigned int busnum)
 
 static int i2c_get_cur_bus(struct udevice **busp)
 {
+#ifdef CONFIG_I2C_SET_DEFAULT_BUS_NUM
+	if (!i2c_cur_bus) {
+		if (cmd_i2c_set_bus_num(CONFIG_I2C_DEFAULT_BUS_NUMBER)) {
+			printf("Default I2C bus %d not found\n",
+			       CONFIG_I2C_DEFAULT_BUS_NUMBER);
+			return -ENODEV;
+		}
+	}
+#endif
+
 	if (!i2c_cur_bus) {
 		puts("No I2C bus selected\n");
 		return -ENODEV;

drivers/i2c/Kconfig

@@ -49,6 +49,20 @@ config I2C_CROS_EC_LDO
 	avoid duplicating the logic in the TPS65090 regulator driver for
 	enabling/disabling an LDO.
 
+config I2C_SET_DEFAULT_BUS_NUM
+	bool "Set default I2C bus number"
+	depends on DM_I2C
+	help
+	  Set default number of I2C bus to be accessed. This option provides
+	  behaviour similar to old (i.e. pre DM) I2C bus driver.
+
+config I2C_DEFAULT_BUS_NUMBER
+	hex "I2C default bus number"
+	depends on I2C_SET_DEFAULT_BUS_NUM
+	default 0x0
+	help
+	  Number of default I2C bus to use
+
 config DM_I2C_GPIO
 	bool "Enable Driver Model for software emulated I2C bus driver"
 	depends on DM_I2C && DM_GPIO