flashrom/raiden_debug_spi.c

/*
 * This file is part of the flashrom project.
 *
 * Copyright 2014, Google Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *    * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *    * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *    * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Alternatively, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") version 2 as published by the Free
 * Software Foundation.
 */

/*
 * This SPI flash programming interface is designed to talk to a Chromium OS
 * device over a Raiden USB connection.  The USB connection is routed to a
 * microcontroller running an image compiled from:
 *
 *     https://chromium.googlesource.com/chromiumos/platform/ec
 *
 * The protocol for the USB-SPI bridge is implemented in the following files
 * in that repository:
 *
 *     chip/stm32/usb_spi.h
 *     chip/stm32/usb_spi.c
 *
 * bInterfaceProtocol determines which protocol is used by the USB SPI device.
 *
 *
 * USB SPI Version 1:
 *
 *     SPI transactions of up to 62B in each direction with every command having
 *     a response. The initial packet from host contains a 2B header indicating
 *     write and read counts with an optional payload length equal to the write
 *     count. The device will respond with a message that reports the 2B status
 *     code and an optional payload response length equal to read count.
 *
 *
 * Message Packets:
 *
 * Command First Packet (Host to Device):
 *
 *      USB SPI command, containing the number of bytes to write and read
 *      and a payload of bytes to write.
 *
 *     +------------------+-----------------+------------------------+
 *     | write count : 1B | read count : 1B | write payload : <= 62B |
 *     +------------------+-----------------+------------------------+
 *
 *     write count:   1 byte, zero based count of bytes to write
 *
 *     read count:    1 byte, zero based count of bytes to read. Full duplex
 *                    mode is enabled with UINT8_MAX
 *
 *     write payload: Up to 62 bytes of data to write to SPI, the total
 *                    length of all TX packets must match write count.
 *                    Due to data alignment constraints, this must be an
 *                    even number of bytes unless this is the final packet.
 *
 * Response Packet (Device to Host):
 *
 *      USB SPI response, containing the status code and any bytes of the
 *      read payload.
 *
 *     +-------------+-----------------------+
 *     | status : 2B | read payload : <= 62B |
 *     +-------------+-----------------------+
 *
 *     status: 2 byte status
 *         0x0000: Success
 *         0x0001: SPI timeout
 *         0x0002: Busy, try again
 *             This can happen if someone else has acquired the shared memory
 *             buffer that the SPI driver uses as /dev/null
 *         0x0003: Write count invalid (over 62 bytes)
 *         0x0004: Read count invalid (over 62 bytes)
 *         0x0005: The SPI bridge is disabled.
 *         0x8000: Unknown error mask
 *             The bottom 15 bits will contain the bottom 15 bits from the EC
 *             error code.
 *
 *     read payload: Up to 62 bytes of data read from SPI, the total
 *                   length of all RX packets must match read count
 *                   unless an error status was returned. Due to data
 *                   alignment constraints, this must be a even number
 *                   of bytes unless this is the final packet.
 *
 *
 * USB Error Codes:
 *
 * send_command return codes have the following format:
 *
 *     0x00000:         Status code success.
 *     0x00001-0x0FFFF: Error code returned by the USB SPI device.
 *     0x10001-0x1FFFF: Error code returned by the USB SPI host.
 *     0x20001-0x20063  Lower bits store the positive value representation
 *                      of the libusb_error enum. See the libusb documentation:
 *                      http://libusb.sourceforge.net/api-1.0/group__misc.html
 */

#include "programmer.h"
#include "spi.h"
#include "usb_device.h"

#include <libusb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

/* FIXME: Add some programmer IDs here */
const struct dev_entry devs_raiden[] = {
	{0},
};

#define GOOGLE_VID                  (0x18D1)
#define GOOGLE_RAIDEN_SPI_SUBCLASS  (0x51)

enum {
	GOOGLE_RAIDEN_SPI_PROTOCOL_V1 = 0x01,
	GOOGLE_RAIDEN_SPI_PROTOCOL_V2 = 0x02,
};

enum {
	/* The host failed to transfer the data with no libusb error. */
	USB_SPI_HOST_TX_BAD_TRANSFER      = 0x10001,
	/* The number of bytes written did not match expected. */
	USB_SPI_HOST_TX_WRITE_FAILURE     = 0x10002,

	/* We did not receive the expected USB packet. */
	USB_SPI_HOST_RX_UNEXPECTED_PACKET = 0x11001,
	/* We received a continue packet with an invalid data index. */
	USB_SPI_HOST_RX_BAD_DATA_INDEX    = 0x11002,
	/* We received too much data. */
	USB_SPI_HOST_RX_DATA_OVERFLOW     = 0x11003,
	/* The number of bytes read did not match expected. */
	USB_SPI_HOST_RX_READ_FAILURE      = 0x11004,

	/* We were unable to configure the device. */
	USB_SPI_HOST_INIT_FAILURE         = 0x12001,
};

enum usb_spi_error {
	USB_SPI_SUCCESS                 = 0x0000,
	USB_SPI_TIMEOUT                 = 0x0001,
	USB_SPI_BUSY                    = 0x0002,
	USB_SPI_WRITE_COUNT_INVALID     = 0x0003,
	USB_SPI_READ_COUNT_INVALID      = 0x0004,
	USB_SPI_DISABLED                = 0x0005,
	USB_SPI_UNKNOWN_ERROR           = 0x8000,
};

enum raiden_debug_spi_request {
	RAIDEN_DEBUG_SPI_REQ_ENABLE    = 0x0000,
	RAIDEN_DEBUG_SPI_REQ_DISABLE   = 0x0001,
	RAIDEN_DEBUG_SPI_REQ_ENABLE_AP = 0x0002,
	RAIDEN_DEBUG_SPI_REQ_ENABLE_EC = 0x0003,
};

#define PACKET_HEADER_SIZE      (2)
#define USB_MAX_PACKET_SIZE     (64)
#define PAYLOAD_SIZE_V1         (USB_MAX_PACKET_SIZE - PACKET_HEADER_SIZE)
#define SPI_TRANSFER_V1_MAX     (PAYLOAD_SIZE_V1)

/*
 * Servo Micro has an error where it is capable of acknowledging USB packets
 * without loading it into the USB endpoint buffers or triggering interrupts.
 * See crbug.com/952494. Retry mechanisms have been implemented to recover
 * from these rare failures allowing the process to continue.
 */
#define WRITE_RETRY_ATTEMPTS    (3)
#define READ_RETRY_ATTEMPTS     (3)
#define RETRY_INTERVAL_US       (100 * 1000)

/*
 * This timeout is so large because the Raiden SPI timeout is 800ms.
 */
#define TRANSFER_TIMEOUT_MS     (200 + 800)

struct raiden_debug_spi_data {
	struct usb_device *dev;
	uint8_t in_ep;
	uint8_t out_ep;
	uint8_t protocol_version;
	/*
	 * Note: Due to bugs, flashrom does not always treat the max_data_write
	 * and max_data_read counts as the maximum packet size. As a result, we
	 * have to store a local copy of the actual max packet sizes and validate
	 * against it when performing transfers.
	 */
	uint16_t max_spi_write_count;
	uint16_t max_spi_read_count;
};

/*
 * Version 1 protocol specific attributes
 */

struct usb_spi_command_v1 {
	uint8_t write_count;
	/* UINT8_MAX indicates full duplex mode on compliant devices. */
	uint8_t read_count;
	uint8_t data[PAYLOAD_SIZE_V1];
} __attribute__((packed));

struct usb_spi_response_v1 {
	uint16_t status_code;
	uint8_t data[PAYLOAD_SIZE_V1];
} __attribute__((packed));

union usb_spi_packet_v1 {
	struct usb_spi_command_v1 command;
	struct usb_spi_response_v1 response;
} __attribute__((packed));

struct usb_spi_packet_ctx {
	union {
		uint8_t bytes[USB_MAX_PACKET_SIZE];
		union usb_spi_packet_v1 packet_v1;
	};
	/*
	 * By storing the number of bytes in the header and knowing that the
	 * USB data packets are all 64B long, we are able to use the header
	 * size to store the offset of the buffer and it's size without
	 * duplicating variables that can go out of sync.
	 */
	size_t header_size;
	/* Number of bytes in the packet */
	size_t packet_size;
};

struct usb_spi_transmit_ctx {
	/* Buffer we are reading data from. */
	const uint8_t *buffer;
	/* Number of bytes in the transfer. */
	size_t transmit_size;
	/* Number of bytes transferred. */
	size_t transmit_index;
};

struct usb_spi_receive_ctx {
	/* Buffer we are writing data into. */
	uint8_t *buffer;
	/* Number of bytes in the transfer. */
	size_t receive_size;
	/* Number of bytes transferred. */
	size_t receive_index;
};

/*
 * This function will return true when an error code can potentially recover
 * if we attempt to write SPI data to the device or read from it. We know
 * that some conditions are not recoverable in the current state so allows us
 * to bypass the retry logic and terminate early.
 */
static bool retry_recovery(int error_code)
{
	if (error_code < 0x10000) {
		/*
		 * Handle error codes returned from the device. USB_SPI_TIMEOUT,
		 * USB_SPI_BUSY, and USB_SPI_WRITE_COUNT_INVALID have been observed
		 * during transfer errors to the device and can be recovered.
		 */
		if (USB_SPI_READ_COUNT_INVALID <= error_code &&
		    error_code <= USB_SPI_DISABLED) {
			return false;
		}
	} else if (usb_device_is_libusb_error(error_code)) {
		/* Handle error codes returned from libusb. */
		if (error_code == LIBUSB_ERROR(LIBUSB_ERROR_NO_DEVICE)) {
			return false;
		}
	}
	return true;
}

static struct raiden_debug_spi_data *
	get_raiden_data_from_context(const struct flashctx *flash)
{
	return (struct raiden_debug_spi_data *)flash->mst->spi.data;
}

/*
 * Read data into the receive buffer.
 *
 * @param dst       Destination receive context we are writing data to.
 * @param src       Source packet context we are reading data from.
 *
 * @returns         status code 0 on success.
 *                  USB_SPI_HOST_RX_DATA_OVERFLOW if the source packet is too
 *                  large to fit in read buffer.
 */
static int read_usb_packet(struct usb_spi_receive_ctx *dst,
		const struct usb_spi_packet_ctx *src)
{
	size_t max_read_length = dst->receive_size - dst->receive_index;
	size_t bytes_in_buffer = src->packet_size - src->header_size;
	const uint8_t *packet_buffer = src->bytes + src->header_size;

	if (bytes_in_buffer > max_read_length) {
		/*
		 * An error occurred, we should not receive more data than
		 * the buffer can support.
		 */
		msg_perr("Raiden: Receive packet overflowed\n"
				"    bytes_in_buffer = %zu\n"
				"    max_read_length = %zu\n"
				"    receive_index   = %zu\n"
				"    receive_size    = %zu\n",
				bytes_in_buffer, max_read_length,
				dst->receive_size, dst->receive_index);
		return USB_SPI_HOST_RX_DATA_OVERFLOW;
	}
	memcpy(dst->buffer + dst->receive_index, packet_buffer,
		bytes_in_buffer);

	dst->receive_index += bytes_in_buffer;
	return 0;
}

/*
 * Fill the USB packet with data from the transmit buffer.
 *
 * @param dst       Destination packet context we are writing data to.
 * @param src       Source transmit context we are reading data from.
 */
static void fill_usb_packet(struct usb_spi_packet_ctx *dst,
		struct usb_spi_transmit_ctx *src)
{
	size_t transmit_size = src->transmit_size - src->transmit_index;
	size_t max_buffer_size = USB_MAX_PACKET_SIZE - dst->header_size;
	uint8_t *packet_buffer = dst->bytes + dst->header_size;

	if (transmit_size > max_buffer_size)
		transmit_size = max_buffer_size;

	memcpy(packet_buffer, src->buffer + src->transmit_index, transmit_size);

	dst->packet_size = dst->header_size + transmit_size;
	src->transmit_index += transmit_size;
}

/*
 * Receive the data from the device USB endpoint and store in the packet.
 *
 * @param ctx_data      Raiden SPI config.
 * @param packet        Destination packet used to store the endpoint data.
 *
 * @returns             Returns status code with 0 on success.
 */
static int receive_packet(const struct raiden_debug_spi_data *ctx_data,
		struct usb_spi_packet_ctx *packet)
{
	int received;
	int status = LIBUSB(libusb_bulk_transfer(ctx_data->dev->handle,
				ctx_data->in_ep,
				packet->bytes,
				USB_MAX_PACKET_SIZE,
				&received,
				TRANSFER_TIMEOUT_MS));
	packet->packet_size = received;
	if (status) {
		msg_perr("Raiden: IN transfer failed\n"
			 "    received = %d\n"
			 "    status   = 0x%05x\n",
			 received, status);
	}
	return status;
}

/*
 * Transmit data from the packet to the device's USB endpoint.
 *
 * @param ctx_data      Raiden SPI config.
 * @param packet        Source packet we will write to the endpoint data.
 *
 * @returns             Returns status code with 0 on success.
 */
static int transmit_packet(const struct raiden_debug_spi_data *ctx_data,
		struct usb_spi_packet_ctx *packet)
{
	int transferred;
	int status = LIBUSB(libusb_bulk_transfer(ctx_data->dev->handle,
				ctx_data->out_ep,
				packet->bytes,
				packet->packet_size,
				&transferred,
				TRANSFER_TIMEOUT_MS));
	if (status || (size_t)transferred != packet->packet_size) {
		if (!status) {
			/* No error was reported, but we didn't transmit the data expected. */
			status = USB_SPI_HOST_TX_BAD_TRANSFER;
		}
		msg_perr("Raiden: OUT transfer failed\n"
			 "    transferred = %d\n"
			 "    packet_size = %zu\n"
			 "    status      = 0x%05x\n",
			 transferred, packet->packet_size, status);

	}
	return status;
}

/*
 * Version 1 protocol command to start a USB SPI transfer and write the payload.
 *
 * @param ctx_data      Raiden SPI config.
 * @param write         Write context of data to transmit and write payload.
 * @param read          Read context of data to receive and read buffer.
 *
 * @returns             Returns status code with 0 on success.
 */
static int write_command_v1(const struct raiden_debug_spi_data *ctx_data,
		struct usb_spi_transmit_ctx *write,
		struct usb_spi_receive_ctx *read)
{
	struct usb_spi_packet_ctx command = {
		.header_size = offsetof(struct usb_spi_command_v1, data),
		.packet_v1.command.write_count = write->transmit_size,
		.packet_v1.command.read_count = read->receive_size
	};

	/* Reset the write context to the start. */
	write->transmit_index = 0;

	fill_usb_packet(&command, write);
	return transmit_packet(ctx_data, &command);
}

/*
 * Version 1 Protocol: Responsible for reading the response of the USB SPI
 * transfer. Status codes from the transfer and any read payload are copied
 * to the read_buffer.
 *
 * @param ctx_data      Raiden SPI config.
 * @param write         Write context of data to transmit and write payload.
 * @param read          Read context of data to receive and read buffer.
 *
 * @returns             Returns status code with 0 on success.
 */
static int read_response_v1(const struct raiden_debug_spi_data *ctx_data,
		struct usb_spi_transmit_ctx *write,
		struct usb_spi_receive_ctx *read)
{
	int status;
	struct usb_spi_packet_ctx response;

	/* Reset the read context to the start. */
	read->receive_index = 0;

	status = receive_packet(ctx_data, &response);
	if (status) {
		/* Return the transfer error since the status_code is unreliable */
		return status;
	}
	if (response.packet_v1.response.status_code) {
		return response.packet_v1.response.status_code;
	}
	response.header_size = offsetof(struct usb_spi_response_v1, data);

	status = read_usb_packet(read, &response);
	return status;
}

/*
 * Version 1 Protocol: Sets up a USB SPI transfer, transmits data to the device,
 * reads the status code and any payload from the device. This will also handle
 * recovery if an error has occurred.
 *
 * @param flash         Flash context storing SPI capabilities and USB device
 *                      information.
 * @param write_count   Number of bytes to write
 * @param read_count    Number of bytes to read
 * @param write_buffer  Address of write buffer
 * @param read_buffer   Address of buffer to store read data
 *
 * @returns             Returns status code with 0 on success.
 */
static int send_command_v1(const struct flashctx *flash,
		unsigned int write_count,
		unsigned int read_count,
		const unsigned char *write_buffer,
		unsigned char *read_buffer)
{
	int status = -1;

	struct usb_spi_transmit_ctx write_ctx = {
		.buffer = write_buffer,
		.transmit_size = write_count
	};
	struct usb_spi_receive_ctx read_ctx = {
		.buffer = read_buffer,
		.receive_size = read_count
	};
	const struct raiden_debug_spi_data *ctx_data = get_raiden_data_from_context(flash);

	if (write_count > ctx_data->max_spi_write_count) {
		msg_perr("Raiden: Invalid write count\n"
			 "    write count = %u\n"
			 "    max write   = %d\n",
			 write_count, ctx_data->max_spi_write_count);
		return SPI_INVALID_LENGTH;
	}

	if (read_count > ctx_data->max_spi_read_count) {
		msg_perr("Raiden: Invalid read count\n"
			 "    read count = %d\n"
			 "    max read   = %d\n",
			 read_count, ctx_data->max_spi_read_count);
		return SPI_INVALID_LENGTH;
	}

	for (unsigned int write_attempt = 0; write_attempt < WRITE_RETRY_ATTEMPTS;
	         write_attempt++) {


		status = write_command_v1(ctx_data, &write_ctx, &read_ctx);

		if (!status &&
			(write_ctx.transmit_index != write_ctx.transmit_size)) {
			/* No errors were reported, but write is incomplete. */
			status = USB_SPI_HOST_TX_WRITE_FAILURE;
		}

		if (status) {
			/* Write operation failed. */
			msg_perr("Raiden: Write command failed\n"
				 "    write count       = %u\n"
				 "    read count        = %u\n"
				 "    transmitted bytes = %zu\n"
				 "    write attempt     = %u\n"
				 "    status            = 0x%05x\n",

				 write_count, read_count, write_ctx.transmit_index,
				 write_attempt + 1, status);
			if (!retry_recovery(status)) {
				/* Reattempting will not result in a recovery. */
				return status;
			}
			programmer_delay(RETRY_INTERVAL_US);
			continue;
		}
		for (unsigned int read_attempt = 0; read_attempt < READ_RETRY_ATTEMPTS;
				read_attempt++) {

			status = read_response_v1(ctx_data, &write_ctx, &read_ctx);

			if (!status) {
				if (read_ctx.receive_size == read_ctx.receive_index) {
					/* Successful transfer. */
					return status;
				} else {
					/* Report the error from the failed read. */
					status = USB_SPI_HOST_RX_READ_FAILURE;
				}
			}

			if (status) {
				/* Read operation failed. */
				msg_perr("Raiden: Read response failed\n"
					 "    write count    = %u\n"
					 "    read count     = %u\n"
					 "    received bytes = %zu\n"
					 "    write attempt  = %u\n"
					 "    read attempt   = %u\n"
					 "    status         = 0x%05x\n",
					 write_count, read_count, read_ctx.receive_index,
					 write_attempt + 1, read_attempt + 1, status);
				if (!retry_recovery(status)) {
					/* Reattempting will not result in a recovery. */
					return status;
				}
				programmer_delay(RETRY_INTERVAL_US);
			}
		}
	}
	return status;
}

static const struct spi_master spi_master_raiden_debug = {
	.features       = SPI_MASTER_4BA,
	.max_data_read  = 0,
	.max_data_write = 0,
	.command        = NULL,
	.multicommand   = default_spi_send_multicommand,
	.read           = default_spi_read,
	.write_256      = default_spi_write_256,
	.write_aai      = default_spi_write_aai,
};

static int match_endpoint(struct libusb_endpoint_descriptor const *descriptor,
                          enum libusb_endpoint_direction direction)
{
	return (((descriptor->bEndpointAddress & LIBUSB_ENDPOINT_DIR_MASK) ==
		 direction) &&
		((descriptor->bmAttributes & LIBUSB_TRANSFER_TYPE_MASK) ==
		 LIBUSB_TRANSFER_TYPE_BULK));
}

static int find_endpoints(struct usb_device *dev, uint8_t *in_ep, uint8_t *out_ep)
{
	int i;
	int in_count  = 0;
	int out_count = 0;

	for (i = 0; i < dev->interface_descriptor->bNumEndpoints; i++) {
		struct libusb_endpoint_descriptor const  *endpoint =
			&dev->interface_descriptor->endpoint[i];

		if (match_endpoint(endpoint, LIBUSB_ENDPOINT_IN)) {
			in_count++;
			*in_ep = endpoint->bEndpointAddress;
		} else if (match_endpoint(endpoint, LIBUSB_ENDPOINT_OUT)) {
			out_count++;
			*out_ep = endpoint->bEndpointAddress;
		}
	}

	if (in_count != 1 || out_count != 1) {
		msg_perr("Raiden: Failed to find one IN and one OUT endpoint\n"
			 "        found %d IN and %d OUT endpoints\n",
			 in_count,
			 out_count);
		return 1;
	}

	msg_pdbg("Raiden: Found IN  endpoint = 0x%02x\n", *in_ep);
	msg_pdbg("Raiden: Found OUT endpoint = 0x%02x\n", *out_ep);

	return 0;
}

/*
 * Configure the USB SPI master based on the device we are connected to.
 * It will use the device's bInterfaceProtocol to identify which protocol
 * is being used by the device USB SPI interface and if needed query the
 * device for its capabilities.
 *
 * @param spi_config    Raiden SPI config which will be modified.
 *
 * @returns             Returns status code with 0 on success.
 */
static int configure_protocol(struct spi_master *spi_config)
{
	struct raiden_debug_spi_data *ctx_data =
		(struct raiden_debug_spi_data *)spi_config->data;

	ctx_data->protocol_version =
		ctx_data->dev->interface_descriptor->bInterfaceProtocol;

	switch (ctx_data->protocol_version) {
	case GOOGLE_RAIDEN_SPI_PROTOCOL_V1:
		/*
		 * Protocol V1 is supported by adjusting the max data
		 * read and write sizes which results in no continue packets.
		 */
		spi_config->command = send_command_v1;
		ctx_data->max_spi_write_count = SPI_TRANSFER_V1_MAX;
		ctx_data->max_spi_read_count = SPI_TRANSFER_V1_MAX;
		break;
	default:
		msg_pdbg("Raiden: Unknown USB SPI protocol version = %d",
		         ctx_data->protocol_version);
		return USB_SPI_HOST_INIT_FAILURE;
	}

	/*
	 * Unfortunately there doesn't seem to be a way to specify the maximum number
	 * of bytes that your SPI device can read/write, these values are the maximum
	 * data chunk size that flashrom will package up with an additional five bytes
	 * of command for the flash device.
	 *
	 * The largest command that flashrom generates is the byte program command, so
	 * we use that command header maximum size here. If we didn't include the
	 * offset, flashrom may request a SPI transfer that is too large for the SPI
	 * device to support.
	 */
	spi_config->max_data_write = ctx_data->max_spi_write_count -
		JEDEC_BYTE_PROGRAM_OUTSIZE;
	spi_config->max_data_read = ctx_data->max_spi_read_count -
		JEDEC_BYTE_PROGRAM_OUTSIZE;

	return 0;
}

static int raiden_debug_spi_shutdown(void * data)
{
	struct spi_master *spi_config = data;
	struct raiden_debug_spi_data *ctx_data =
		(struct raiden_debug_spi_data *)spi_config->data;

	int ret = LIBUSB(libusb_control_transfer(
				ctx_data->dev->handle,
				LIBUSB_ENDPOINT_OUT |
				LIBUSB_REQUEST_TYPE_VENDOR |
				LIBUSB_RECIPIENT_INTERFACE,
				RAIDEN_DEBUG_SPI_REQ_DISABLE,
				0,
				ctx_data->dev->interface_descriptor->bInterfaceNumber,
				NULL,
				0,
				TRANSFER_TIMEOUT_MS));
	if (ret != 0) {
		msg_perr("Raiden: Failed to disable SPI bridge\n");
		free(ctx_data);
		free(spi_config);
		return ret;
	}

	usb_device_free(ctx_data->dev);
	libusb_exit(NULL);
	free(ctx_data);
	free(spi_config);

	return 0;
}

static int get_target(void)
{
	int request_enable = RAIDEN_DEBUG_SPI_REQ_ENABLE;

	char *target_str = extract_programmer_param("target");
	if (target_str) {
		if (!strcasecmp(target_str, "ap"))
			request_enable = RAIDEN_DEBUG_SPI_REQ_ENABLE_AP;
		else if (!strcasecmp(target_str, "ec"))
			request_enable = RAIDEN_DEBUG_SPI_REQ_ENABLE_EC;
		else {
			msg_perr("Invalid target: %s\n", target_str);
			request_enable = -1;
		}
	}
	free(target_str);

	return request_enable;
}

static void free_dev_list(struct usb_device **dev_lst)
{
	struct usb_device *dev = *dev_lst;
	/* free devices we don't care about */
	dev = dev->next;
	while (dev)
		dev = usb_device_free(dev);
}

int raiden_debug_spi_init(void)
{
	struct usb_match match;
	char *serial = extract_programmer_param("serial");
	struct usb_device *current;
	struct usb_device *device = NULL;
	int found = 0;
	int ret;

	int request_enable = get_target();
	if (request_enable < 0) {
		free(serial);
		return 1;
	}

	usb_match_init(&match);

	usb_match_value_default(&match.vid,      GOOGLE_VID);
	usb_match_value_default(&match.class,    LIBUSB_CLASS_VENDOR_SPEC);
	usb_match_value_default(&match.subclass, GOOGLE_RAIDEN_SPI_SUBCLASS);
	usb_match_value_default(&match.protocol, GOOGLE_RAIDEN_SPI_PROTOCOL_V1);

	ret = LIBUSB(libusb_init(NULL));
	if (ret != 0) {
		msg_perr("Raiden: libusb_init failed\n");
		free(serial);
		return ret;
	}

	ret = usb_device_find(&match, &current);
	if (ret != 0) {
		msg_perr("Raiden: Failed to find devices\n");
		free(serial);
		return ret;
	}

	uint8_t in_endpoint  = 0;
	uint8_t out_endpoint = 0;
	while (current) {
		device = current;

		if (find_endpoints(device, &in_endpoint, &out_endpoint)) {
			msg_pdbg("Raiden: Failed to find valid endpoints on device");
			usb_device_show(" ", current);
			goto loop_end;
		}

		if (usb_device_claim(device)) {
			msg_pdbg("Raiden: Failed to claim USB device");
			usb_device_show(" ", current);
			goto loop_end;
		}

		if (!serial) {
			found = 1;
			goto loop_end;
		} else {
			unsigned char dev_serial[32];
			struct libusb_device_descriptor descriptor;
			int rc;

			memset(dev_serial, 0, sizeof(dev_serial));

			if (libusb_get_device_descriptor(device->device, &descriptor)) {
				msg_pdbg("USB: Failed to get device descriptor.\n");
				goto loop_end;
			}

			rc = libusb_get_string_descriptor_ascii(device->handle,
					descriptor.iSerialNumber,
					dev_serial,
					sizeof(dev_serial));
			if (rc < 0) {
				LIBUSB(rc);
			} else {
				if (strcmp(serial, (char *)dev_serial)) {
					msg_pdbg("Raiden: Serial number %s did not match device", serial);
					usb_device_show(" ", current);
				} else {
					msg_pinfo("Raiden: Serial number %s matched device", serial);
					usb_device_show(" ", current);
					found = 1;
				}
			}
		}

loop_end:
		if (found)
			break;
		else
			current = usb_device_free(current);
	}

	if (!device || !found) {
		msg_perr("Raiden: No usable device found.\n");
		free(serial);
		return 1;
	}

	free_dev_list(&current);

	ret = LIBUSB(libusb_control_transfer(
				device->handle,
				LIBUSB_ENDPOINT_OUT |
				LIBUSB_REQUEST_TYPE_VENDOR |
				LIBUSB_RECIPIENT_INTERFACE,
				request_enable,
				0,
				device->interface_descriptor->bInterfaceNumber,
				NULL,
				0,
				TRANSFER_TIMEOUT_MS));
	if (ret != 0) {
		msg_perr("Raiden: Failed to enable SPI bridge\n");
		return ret;
	}

	/*
	 * Allow for power to settle on the AP and EC flash devices.
	 * Load switches can have a 1-3 ms turn on time, and SPI flash devices
	 * can require up to 10 ms from power on to the first write.
	 */
	if ((request_enable == RAIDEN_DEBUG_SPI_REQ_ENABLE_AP) ||
		(request_enable == RAIDEN_DEBUG_SPI_REQ_ENABLE_EC))
		usleep(50 * 1000);

	struct spi_master *spi_config = calloc(1, sizeof(struct spi_master));
	if (!spi_config) {
		msg_perr("Unable to allocate space for SPI master.\n");
		return SPI_GENERIC_ERROR;
	}
	struct raiden_debug_spi_data *data = calloc(1, sizeof(struct raiden_debug_spi_data));
	if (!data) {
		free(spi_config);
		msg_perr("Unable to allocate space for extra SPI master data.\n");
		return SPI_GENERIC_ERROR;
	}

	memcpy(spi_config, &spi_master_raiden_debug, sizeof(struct spi_master));

	data->dev = device;
	data->in_ep = in_endpoint;
	data->out_ep = out_endpoint;

	spi_config->data = data;
	/*
	 * The SPI master needs to be configured based on the device connected.
	 * Using the device protocol interrogation, we will set the limits on
	 * the write and read sizes and switch command functions.
	 */
	ret = configure_protocol(spi_config);
	if (ret) {
		msg_perr("Raiden: Error configuring protocol\n"
			 "    protocol       = %u\n"
			 "    status         = 0x%05x\n",
			 data->dev->interface_descriptor->bInterfaceProtocol, ret);
		free(data);
		free(spi_config);
		return SPI_GENERIC_ERROR;
	}

	register_spi_master(spi_config);
	register_shutdown(raiden_debug_spi_shutdown, spi_config);

	return 0;
}