cros_ec: sandbox: Add Chrome OS EC emulation

Add a simple emulation of the Chrome OS EC for sandbox, so that it can
perform various EC tasks such as keyboard handling.

Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/misc/Makefile

@@ -11,6 +11,7 @@ obj-$(CONFIG_CBMEM_CONSOLE) += cbmem_console.o
 obj-$(CONFIG_CROS_EC) += cros_ec.o
 obj-$(CONFIG_CROS_EC_LPC) += cros_ec_lpc.o
 obj-$(CONFIG_CROS_EC_I2C) += cros_ec_i2c.o
+obj-$(CONFIG_CROS_EC_SANDBOX) += cros_ec_sandbox.o
 obj-$(CONFIG_CROS_EC_SPI) += cros_ec_spi.o
 obj-$(CONFIG_FSL_IIM) += fsl_iim.o
 obj-$(CONFIG_GPIO_LED) += gpio_led.o

drivers/misc/cros_ec.c

@@ -223,6 +223,11 @@ static int send_command_proto3(struct cros_ec_dev *dev,
 	case CROS_EC_IF_SPI:
 		rv = cros_ec_spi_packet(dev, out_bytes, in_bytes);
 		break;
+#endif
+#ifdef CONFIG_CROS_EC_SANDBOX
+	case CROS_EC_IF_SANDBOX:
+		rv = cros_ec_sandbox_packet(dev, out_bytes, in_bytes);
+		break;
 #endif
 	case CROS_EC_IF_NONE:
 	/* TODO: support protocol 3 for LPC, I2C; for now fall through */
@@ -1032,6 +1037,11 @@ static int cros_ec_decode_fdt(const void *blob, int node,
 	case COMPAT_INTEL_LPC:
 		dev->interface = CROS_EC_IF_LPC;
 		break;
+#endif
+#ifdef CONFIG_CROS_EC_SANDBOX
+	case COMPAT_SANDBOX_HOST_EMULATION:
+		dev->interface = CROS_EC_IF_SANDBOX;
+		break;
 #endif
 	default:
 		debug("%s: Unknown compat id %d\n", __func__, compat);
@@ -1087,6 +1097,12 @@ int cros_ec_init(const void *blob, struct cros_ec_dev **cros_ecp)
 		if (cros_ec_lpc_init(dev, blob))
 			return -CROS_EC_ERR_DEV_INIT;
 		break;
+#endif
+#ifdef CONFIG_CROS_EC_SANDBOX
+	case CROS_EC_IF_SANDBOX:
+		if (cros_ec_sandbox_init(dev, blob))
+			return -CROS_EC_ERR_DEV_INIT;
+		break;
 #endif
 	case CROS_EC_IF_NONE:
 	default:

drivers/misc/cros_ec_sandbox.c

@@ -0,0 +1,559 @@
+/*
+ * Chromium OS cros_ec driver - sandbox emulation
+ *
+ * Copyright (c) 2013 The Chromium OS Authors.
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <cros_ec.h>
+#include <ec_commands.h>
+#include <errno.h>
+#include <hash.h>
+#include <malloc.h>
+#include <os.h>
+#include <sha256.h>
+#include <spi.h>
+#include <asm/state.h>
+#include <asm/sdl.h>
+#include <linux/input.h>
+
+/*
+ * Ultimately it shold be possible to connect an Chrome OS EC emulation
+ * to U-Boot and remove all of this code. But this provides a test
+ * environment for bringing up chromeos_sandbox and demonstrating its
+ * utility.
+ *
+ * This emulation includes the following:
+ *
+ * 1. Emulation of the keyboard, by converting keypresses received from SDL
+ * into key scan data, passed back from the EC as key scan messages. The
+ * key layout is read from the device tree.
+ *
+ * 2. Emulation of vboot context - so this can be read/written as required.
+ *
+ * 3. Save/restore of EC state, so that the vboot context, flash memory
+ * contents and current image can be preserved across boots. This is important
+ * since the EC is supposed to continue running even if the AP resets.
+ *
+ * 4. Some event support, in particular allowing Escape to be pressed on boot
+ * to enter recovery mode. The EC passes this to U-Boot through the normal
+ * event message.
+ *
+ * 5. Flash read/write/erase support, so that software sync works. The
+ * protect messages are supported but no protection is implemented.
+ *
+ * 6. Hashing of the EC image, again to support software sync.
+ *
+ * Other features can be added, although a better path is probably to link
+ * the EC image in with U-Boot (Vic has demonstrated a prototype for this).
+ */
+
+DECLARE_GLOBAL_DATA_PTR;
+
+#define KEYBOARD_ROWS	8
+#define KEYBOARD_COLS	13
+
+/* A single entry of the key matrix */
+struct ec_keymatrix_entry {
+	int row;	/* key matrix row */
+	int col;	/* key matrix column */
+	int keycode;	/* corresponding linux key code */
+};
+
+/**
+ * struct ec_state - Information about the EC state
+ *
+ * @vbnv_context: Vboot context data stored by EC
+ * @ec_config: FDT config information about the EC (e.g. flashmap)
+ * @flash_data: Contents of flash memory
+ * @flash_data_len: Size of flash memory
+ * @current_image: Current image the EC is running
+ * @matrix_count: Number of keys to decode in matrix
+ * @matrix: Information about keyboard matrix
+ * @keyscan: Current keyscan information (bit set for each row/column pressed)
+ * @recovery_req: Keyboard recovery requested
+ */
+struct ec_state {
+	uint8_t vbnv_context[EC_VBNV_BLOCK_SIZE];
+	struct fdt_cros_ec ec_config;
+	uint8_t *flash_data;
+	int flash_data_len;
+	enum ec_current_image current_image;
+	int matrix_count;
+	struct ec_keymatrix_entry *matrix;	/* the key matrix info */
+	uint8_t keyscan[KEYBOARD_COLS];
+	bool recovery_req;
+} s_state, *state;
+
+/**
+ * cros_ec_read_state() - read the sandbox EC state from the state file
+ *
+ * If data is available, then blob and node will provide access to it. If
+ * not this function sets up an empty EC.
+ *
+ * @param blob: Pointer to device tree blob, or NULL if no data to read
+ * @param node: Node offset to read from
+ */
+static int cros_ec_read_state(const void *blob, int node)
+{
+	struct ec_state *ec = &s_state;
+	const char *prop;
+	int len;
+
+	/* Set everything to defaults */
+	ec->current_image = EC_IMAGE_RO;
+	if (!blob)
+		return 0;
+
+	/* Read the data if available */
+	ec->current_image = fdtdec_get_int(blob, node, "current-image",
+					   EC_IMAGE_RO);
+	prop = fdt_getprop(blob, node, "vbnv-context", &len);
+	if (prop && len == sizeof(ec->vbnv_context))
+		memcpy(ec->vbnv_context, prop, len);
+
+	prop = fdt_getprop(blob, node, "flash-data", &len);
+	if (prop) {
+		ec->flash_data_len = len;
+		ec->flash_data = os_malloc(len);
+		if (!ec->flash_data)
+			return -ENOMEM;
+		memcpy(ec->flash_data, prop, len);
+		debug("%s: Loaded EC flash data size %#x\n", __func__, len);
+	}
+
+	return 0;
+}
+
+/**
+ * cros_ec_write_state() - Write out our state to the state file
+ *
+ * The caller will ensure that there is a node ready for the state. The node
+ * may already contain the old state, in which case it is overridden.
+ *
+ * @param blob: Device tree blob holding state
+ * @param node: Node to write our state into
+ */
+static int cros_ec_write_state(void *blob, int node)
+{
+	struct ec_state *ec = &s_state;
+
+	/* We are guaranteed enough space to write basic properties */
+	fdt_setprop_u32(blob, node, "current-image", ec->current_image);
+	fdt_setprop(blob, node, "vbnv-context", ec->vbnv_context,
+		    sizeof(ec->vbnv_context));
+	return state_setprop(node, "flash-data", ec->flash_data,
+			     ec->ec_config.flash.length);
+}
+
+SANDBOX_STATE_IO(cros_ec, "google,cros-ec", cros_ec_read_state,
+		 cros_ec_write_state);
+
+/**
+ * Return the number of bytes used in the specified image.
+ *
+ * This is the actual size of code+data in the image, as opposed to the
+ * amount of space reserved in flash for that image. This code is similar to
+ * that used by the real EC code base.
+ *
+ * @param ec	Current emulated EC state
+ * @param entry	Flash map entry containing the image to check
+ * @return actual image size in bytes, 0 if the image contains no content or
+ * error.
+ */
+static int get_image_used(struct ec_state *ec, struct fmap_entry *entry)
+{
+	int size;
+
+	/*
+	 * Scan backwards looking for 0xea byte, which is by definition the
+	 * last byte of the image.  See ec.lds.S for how this is inserted at
+	 * the end of the image.
+	 */
+	for (size = entry->length - 1;
+	     size > 0 && ec->flash_data[entry->offset + size] != 0xea;
+	     size--)
+		;
+
+	return size ? size + 1 : 0;  /* 0xea byte IS part of the image */
+}
+
+/**
+ * Read the key matrix from the device tree
+ *
+ * Keymap entries in the fdt take the form of 0xRRCCKKKK where
+ * RR=Row CC=Column KKKK=Key Code
+ *
+ * @param ec	Current emulated EC state
+ * @param blob	Device tree blob containing keyscan information
+ * @param node	Keyboard node of device tree containing keyscan information
+ * @return 0 if ok, -1 on error
+ */
+static int keyscan_read_fdt_matrix(struct ec_state *ec, const void *blob,
+				   int node)
+{
+	const u32 *cell;
+	int upto;
+	int len;
+
+	cell = fdt_getprop(blob, node, "linux,keymap", &len);
+	ec->matrix_count = len / 4;
+	ec->matrix = calloc(ec->matrix_count, sizeof(*ec->matrix));
+	if (!ec->matrix) {
+		debug("%s: Out of memory for key matrix\n", __func__);
+		return -1;
+	}
+
+	/* Now read the data */
+	for (upto = 0; upto < ec->matrix_count; upto++) {
+		struct ec_keymatrix_entry *matrix = &ec->matrix[upto];
+		u32 word;
+
+		word = fdt32_to_cpu(*cell++);
+		matrix->row = word >> 24;
+		matrix->col = (word >> 16) & 0xff;
+		matrix->keycode = word & 0xffff;
+
+		/* Hard-code some sanity limits for now */
+		if (matrix->row >= KEYBOARD_ROWS ||
+		    matrix->col >= KEYBOARD_COLS) {
+			debug("%s: Matrix pos out of range (%d,%d)\n",
+			      __func__, matrix->row, matrix->col);
+			return -1;
+		}
+	}
+
+	if (upto != ec->matrix_count) {
+		debug("%s: Read mismatch from key matrix\n", __func__);
+		return -1;
+	}
+
+	return 0;
+}
+
+/**
+ * Return the next keyscan message contents
+ *
+ * @param ec	Current emulated EC state
+ * @param scan	Place to put keyscan bytes for the keyscan message (must hold
+ *		enough space for a full keyscan)
+ * @return number of bytes of valid scan data
+ */
+static int cros_ec_keyscan(struct ec_state *ec, uint8_t *scan)
+{
+	const struct ec_keymatrix_entry *matrix;
+	int bytes = KEYBOARD_COLS;
+	int key[8];	/* allow up to 8 keys to be pressed at once */
+	int count;
+	int i;
+
+	memset(ec->keyscan, '\0', bytes);
+	count = sandbox_sdl_scan_keys(key, ARRAY_SIZE(key));
+
+	/* Look up keycode in matrix */
+	for (i = 0, matrix = ec->matrix; i < ec->matrix_count; i++, matrix++) {
+		bool found;
+		int j;
+
+		for (found = false, j = 0; j < count; j++) {
+			if (matrix->keycode == key[j])
+				found = true;
+		}
+
+		if (found) {
+			debug("%d: %d,%d\n", matrix->keycode, matrix->row,
+			      matrix->col);
+			ec->keyscan[matrix->col] |= 1 << matrix->row;
+		}
+	}
+
+	memcpy(scan, ec->keyscan, bytes);
+	return bytes;
+}
+
+/**
+ * Process an emulated EC command
+ *
+ * @param ec		Current emulated EC state
+ * @param req_hdr	Pointer to request header
+ * @param req_data	Pointer to body of request
+ * @param resp_hdr	Pointer to place to put response header
+ * @param resp_data	Pointer to place to put response data, if any
+ * @return length of response data, or 0 for no response data, or -1 on error
+ */
+static int process_cmd(struct ec_state *ec,
+		       struct ec_host_request *req_hdr, const void *req_data,
+		       struct ec_host_response *resp_hdr, void *resp_data)
+{
+	int len;
+
+	/* TODO(sjg@chromium.org): Check checksums */
+	debug("EC command %#0x\n", req_hdr->command);
+
+	switch (req_hdr->command) {
+	case EC_CMD_HELLO: {
+		const struct ec_params_hello *req = req_data;
+		struct ec_response_hello *resp = resp_data;
+
+		resp->out_data = req->in_data + 0x01020304;
+		len = sizeof(*resp);
+		break;
+	}
+	case EC_CMD_GET_VERSION: {
+		struct ec_response_get_version *resp = resp_data;
+
+		strcpy(resp->version_string_ro, "sandbox_ro");
+		strcpy(resp->version_string_rw, "sandbox_rw");
+		resp->current_image = ec->current_image;
+		debug("Current image %d\n", resp->current_image);
+		len = sizeof(*resp);
+		break;
+	}
+	case EC_CMD_VBNV_CONTEXT: {
+		const struct ec_params_vbnvcontext *req = req_data;
+		struct ec_response_vbnvcontext *resp = resp_data;
+
+		switch (req->op) {
+		case EC_VBNV_CONTEXT_OP_READ:
+			memcpy(resp->block, ec->vbnv_context,
+			       sizeof(resp->block));
+			len = sizeof(*resp);
+			break;
+		case EC_VBNV_CONTEXT_OP_WRITE:
+			memcpy(ec->vbnv_context, resp->block,
+			       sizeof(resp->block));
+			len = 0;
+			break;
+		default:
+			printf("   ** Unknown vbnv_context command %#02x\n",
+			       req->op);
+			return -1;
+		}
+		break;
+	}
+	case EC_CMD_REBOOT_EC: {
+		const struct ec_params_reboot_ec *req = req_data;
+
+		printf("Request reboot type %d\n", req->cmd);
+		switch (req->cmd) {
+		case EC_REBOOT_DISABLE_JUMP:
+			len = 0;
+			break;
+		case EC_REBOOT_JUMP_RW:
+			ec->current_image = EC_IMAGE_RW;
+			len = 0;
+			break;
+		default:
+			puts("   ** Unknown type");
+			return -1;
+		}
+		break;
+	}
+	case EC_CMD_HOST_EVENT_GET_B: {
+		struct ec_response_host_event_mask *resp = resp_data;
+
+		resp->mask = 0;
+		if (ec->recovery_req) {
+			resp->mask |= EC_HOST_EVENT_MASK(
+					EC_HOST_EVENT_KEYBOARD_RECOVERY);
+		}
+
+		len = sizeof(*resp);
+		break;
+	}
+	case EC_CMD_VBOOT_HASH: {
+		const struct ec_params_vboot_hash *req = req_data;
+		struct ec_response_vboot_hash *resp = resp_data;
+		struct fmap_entry *entry;
+		int ret, size;
+
+		entry = &state->ec_config.region[EC_FLASH_REGION_RW];
+
+		switch (req->cmd) {
+		case EC_VBOOT_HASH_RECALC:
+		case EC_VBOOT_HASH_GET:
+			size = SHA256_SUM_LEN;
+			len = get_image_used(ec, entry);
+			ret = hash_block("sha256",
+					 ec->flash_data + entry->offset,
+					 len, resp->hash_digest, &size);
+			if (ret) {
+				printf("   ** hash_block() failed\n");
+				return -1;
+			}
+			resp->status = EC_VBOOT_HASH_STATUS_DONE;
+			resp->hash_type = EC_VBOOT_HASH_TYPE_SHA256;
+			resp->digest_size = size;
+			resp->reserved0 = 0;
+			resp->offset = entry->offset;
+			resp->size = len;
+			len = sizeof(*resp);
+			break;
+		default:
+			printf("   ** EC_CMD_VBOOT_HASH: Unknown command %d\n",
+			       req->cmd);
+			return -1;
+		}
+		break;
+	}
+	case EC_CMD_FLASH_PROTECT: {
+		const struct ec_params_flash_protect *req = req_data;
+		struct ec_response_flash_protect *resp = resp_data;
+		uint32_t expect = EC_FLASH_PROTECT_ALL_NOW |
+				EC_FLASH_PROTECT_ALL_AT_BOOT;
+
+		printf("mask=%#x, flags=%#x\n", req->mask, req->flags);
+		if (req->flags == expect || req->flags == 0) {
+			resp->flags = req->flags ? EC_FLASH_PROTECT_ALL_NOW :
+								0;
+			resp->valid_flags = EC_FLASH_PROTECT_ALL_NOW;
+			resp->writable_flags = 0;
+			len = sizeof(*resp);
+		} else {
+			puts("   ** unexpected flash protect request\n");
+			return -1;
+		}
+		break;
+	}
+	case EC_CMD_FLASH_REGION_INFO: {
+		const struct ec_params_flash_region_info *req = req_data;
+		struct ec_response_flash_region_info *resp = resp_data;
+		struct fmap_entry *entry;
+
+		switch (req->region) {
+		case EC_FLASH_REGION_RO:
+		case EC_FLASH_REGION_RW:
+		case EC_FLASH_REGION_WP_RO:
+			entry = &state->ec_config.region[req->region];
+			resp->offset = entry->offset;
+			resp->size = entry->length;
+			len = sizeof(*resp);
+			printf("EC flash region %d: offset=%#x, size=%#x\n",
+			       req->region, resp->offset, resp->size);
+			break;
+		default:
+			printf("** Unknown flash region %d\n", req->region);
+			return -1;
+		}
+		break;
+	}
+	case EC_CMD_FLASH_ERASE: {
+		const struct ec_params_flash_erase *req = req_data;
+
+		memset(ec->flash_data + req->offset,
+		       ec->ec_config.flash_erase_value,
+		       req->size);
+		len = 0;
+		break;
+	}
+	case EC_CMD_FLASH_WRITE: {
+		const struct ec_params_flash_write *req = req_data;
+
+		memcpy(ec->flash_data + req->offset, req + 1, req->size);
+		len = 0;
+		break;
+	}
+	case EC_CMD_MKBP_STATE:
+		len = cros_ec_keyscan(ec, resp_data);
+		break;
+	default:
+		printf("   ** Unknown EC command %#02x\n", req_hdr->command);
+		return -1;
+	}
+
+	return len;
+}
+
+int cros_ec_sandbox_packet(struct cros_ec_dev *dev, int out_bytes,
+			   int in_bytes)
+{
+	struct ec_host_request *req_hdr = (struct ec_host_request *)dev->dout;
+	const void *req_data = req_hdr + 1;
+	struct ec_host_response *resp_hdr = (struct ec_host_response *)dev->din;
+	void *resp_data = resp_hdr + 1;
+	int len;
+
+	len = process_cmd(&s_state, req_hdr, req_data, resp_hdr, resp_data);
+	if (len < 0)
+		return len;
+
+	resp_hdr->struct_version = 3;
+	resp_hdr->result = EC_RES_SUCCESS;
+	resp_hdr->data_len = len;
+	resp_hdr->reserved = 0;
+	len += sizeof(*resp_hdr);
+	resp_hdr->checksum = 0;
+	resp_hdr->checksum = (uint8_t)
+		-cros_ec_calc_checksum((const uint8_t *)resp_hdr, len);
+
+	return in_bytes;
+}
+
+int cros_ec_sandbox_decode_fdt(struct cros_ec_dev *dev, const void *blob)
+{
+	return 0;
+}
+
+void cros_ec_check_keyboard(struct cros_ec_dev *dev)
+{
+	struct ec_state *ec = &s_state;
+	ulong start;
+
+	printf("Press keys for EC to detect on reset (ESC=recovery)...");
+	start = get_timer(0);
+	while (get_timer(start) < 1000)
+		;
+	putc('\n');
+	if (!sandbox_sdl_key_pressed(KEY_ESC)) {
+		ec->recovery_req = true;
+		printf("   - EC requests recovery\n");
+	}
+}
+
+/**
+ * Initialize sandbox EC emulation.
+ *
+ * @param dev		CROS_EC device
+ * @param blob		Device tree blob
+ * @return 0 if ok, -1 on error
+ */
+int cros_ec_sandbox_init(struct cros_ec_dev *dev, const void *blob)
+{
+	struct ec_state *ec = &s_state;
+	int node;
+	int err;
+
+	state = &s_state;
+	err = cros_ec_decode_ec_flash(blob, &ec->ec_config);
+	if (err)
+		return err;
+
+	node = fdtdec_next_compatible(blob, 0, COMPAT_GOOGLE_CROS_EC_KEYB);
+	if (node < 0) {
+		debug("%s: No cros_ec keyboard found\n", __func__);
+	} else if (keyscan_read_fdt_matrix(ec, blob, node)) {
+		debug("%s: Could not read key matrix\n", __func__);
+		return -1;
+	}
+
+	/* If we loaded EC data, check that the length matches */
+	if (ec->flash_data &&
+	    ec->flash_data_len != ec->ec_config.flash.length) {
+		printf("EC data length is %x, expected %x, discarding data\n",
+		       ec->flash_data_len, ec->ec_config.flash.length);
+		os_free(ec->flash_data);
+		ec->flash_data = NULL;
+	}
+
+	/* Otherwise allocate the memory */
+	if (!ec->flash_data) {
+		ec->flash_data_len = ec->ec_config.flash.length;
+		ec->flash_data = os_malloc(ec->flash_data_len);
+		if (!ec->flash_data)
+			return -ENOMEM;
+	}
+
+	return 0;
+}

include/cros_ec.h

@@ -20,6 +20,7 @@ enum cros_ec_interface_t {
 	CROS_EC_IF_SPI,
 	CROS_EC_IF_I2C,
 	CROS_EC_IF_LPC,	/* Intel Low Pin Count interface */
+	CROS_EC_IF_SANDBOX,
 };
 
 /* Our configuration information */
@@ -237,6 +238,7 @@ struct cros_ec_dev *board_get_cros_ec_dev(void);
 int cros_ec_i2c_init(struct cros_ec_dev *dev, const void *blob);
 int cros_ec_spi_init(struct cros_ec_dev *dev, const void *blob);
 int cros_ec_lpc_init(struct cros_ec_dev *dev, const void *blob);
+int cros_ec_sandbox_init(struct cros_ec_dev *dev, const void *blob);
 
 /**
  * Read information from the fdt for the i2c cros_ec interface
@@ -256,6 +258,15 @@ int cros_ec_i2c_decode_fdt(struct cros_ec_dev *dev, const void *blob);
  */
 int cros_ec_spi_decode_fdt(struct cros_ec_dev *dev, const void *blob);
 
+/**
+ * Read information from the fdt for the sandbox cros_ec interface
+ *
+ * @param dev		CROS-EC device
+ * @param blob		Device tree blob
+ * @return 0 if ok, -1 if we failed to read all required information
+ */
+int cros_ec_sandbox_decode_fdt(struct cros_ec_dev *dev, const void *blob);
+
 /**
  * Check whether the LPC interface supports new-style commands.
  *
@@ -323,6 +334,8 @@ int cros_ec_spi_command(struct cros_ec_dev *dev, uint8_t cmd, int cmd_version,
  * @return number of bytes in response packet, or <0 on error
  */
 int cros_ec_spi_packet(struct cros_ec_dev *dev, int out_bytes, int in_bytes);
+int cros_ec_sandbox_packet(struct cros_ec_dev *dev, int out_bytes,
+			   int in_bytes);
 
 /**
  * Dump a block of data for a command.
@@ -480,4 +493,12 @@ int cros_ec_get_error(void);
  */
 int cros_ec_decode_ec_flash(const void *blob, struct fdt_cros_ec *config);
 
+/**
+ * Check the current keyboard state, in case recovery mode is requested.
+ * This function is for sandbox only.
+ *
+ * @param ec		CROS-EC device
+ */
+void cros_ec_check_keyboard(struct cros_ec_dev *dev);
+
 #endif

include/fdtdec.h

@@ -88,6 +88,7 @@ enum fdt_compat_id {
 	COMPAT_INFINEON_SLB9635_TPM,	/* Infineon SLB9635 TPM */
 	COMPAT_INFINEON_SLB9645_TPM,	/* Infineon SLB9645 TPM */
 	COMPAT_SAMSUNG_EXYNOS5_I2C,	/* Exynos5 High Speed I2C Controller */
+	COMPAT_SANDBOX_HOST_EMULATION,	/* Sandbox emulation of a function */
 
 	COMPAT_COUNT,
 };

lib/fdtdec.c

@@ -61,6 +61,7 @@ static const char * const compat_names[COMPAT_COUNT] = {
 	COMPAT(INFINEON_SLB9635_TPM, "infineon,slb9635-tpm"),
 	COMPAT(INFINEON_SLB9645_TPM, "infineon,slb9645-tpm"),
 	COMPAT(SAMSUNG_EXYNOS5_I2C, "samsung,exynos5-hsi2c"),
+	COMPAT(SANDBOX_HOST_EMULATION, "sandbox,host-emulation"),
 };
 
 const char *fdtdec_get_compatible(enum fdt_compat_id id)