+#define CSD_SPEC_VER_3 3 /* Implements system specification 3.1 - 3.2 - 3.31 */
+#define CSD_SPEC_VER_4 4 /* Implements system specification 4.0 - 4.1 */
+
+/*
+ * EXT_CSD fields
+ */
+
+#define EXT_CSD_BUS_WIDTH 183 /* R/W */
+#define EXT_CSD_HS_TIMING 185 /* R/W */
+#define EXT_CSD_CARD_TYPE 196 /* RO */
+
+/*
+ * EXT_CSD field definitions
+ */
+
+#define EXT_CSD_CMD_SET_NORMAL (1<<0)
+#define EXT_CSD_CMD_SET_SECURE (1<<1)
+#define EXT_CSD_CMD_SET_CPSECURE (1<<2)
+
+#define EXT_CSD_CARD_TYPE_26 (1<<0) /* Card can run at 26MHz */
+#define EXT_CSD_CARD_TYPE_52 (1<<1) /* Card can run at 52MHz */
+
+#define EXT_CSD_BUS_WIDTH_1 0 /* Card is in 1 bit mode */
+#define EXT_CSD_BUS_WIDTH_4 1 /* Card is in 4 bit mode */
+#define EXT_CSD_BUS_WIDTH_8 2 /* Card is in 8 bit mode */
+
+/*
+ * MMC_SWITCH access modes
+ */
+
+#define MMC_SWITCH_MODE_CMD_SET 0x00 /* Change the command set */
+#define MMC_SWITCH_MODE_SET_BITS 0x01 /* Set bits which are 1 in value */
+#define MMC_SWITCH_MODE_CLEAR_BITS 0x02 /* Clear bits which are 1 in value */
+#define MMC_SWITCH_MODE_WRITE_BYTE 0x03 /* Set target to value */
+
+/*
+ * SCR field definitions
+ */