OpenCellular/common/usb_i2c.c

/* Copyright 2016 The Chromium OS Authors. All rights reserved.
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "common.h"
#include "link_defs.h"
#include "registers.h"
#include "i2c.h"
#include "usb_descriptor.h"
#include "util.h"

#include "common.h"
#include "console.h"
#include "consumer.h"
#include "queue.h"
#include "queue_policies.h"
#include "producer.h"
#include "task.h"
#include "usb-stream.h"
#include "usb_i2c.h"


#define CPRINTS(format, args...) cprints(CC_I2C, format, ## args)
#define MAX_BYTES_IN_ONE_READING 254


USB_I2C_CONFIG(i2c,
	       USB_IFACE_I2C,
	       USB_STR_I2C_NAME,
	       USB_EP_I2C)

static int16_t usb_i2c_map_error(int error)
{
	switch (error) {
	case EC_SUCCESS:       return USB_I2C_SUCCESS;
	case EC_ERROR_TIMEOUT: return USB_I2C_TIMEOUT;
	case EC_ERROR_BUSY:    return USB_I2C_BUSY;
	default:               return USB_I2C_UNKNOWN_ERROR | (error & 0x7fff);
	}
}

static uint8_t usb_i2c_read_packet(struct usb_i2c_config const *config)
{
	return QUEUE_REMOVE_UNITS(config->consumer.queue, config->buffer,
		queue_count(config->consumer.queue));
}

static void usb_i2c_write_packet(struct usb_i2c_config const *config,
				 size_t count)
{
	QUEUE_ADD_UNITS(config->tx_queue, config->buffer, count);
}

static uint8_t usb_i2c_executable(struct usb_i2c_config const *config)
{
	/*
	 * In order to support larger write payload, we need to peek
	 * the queue to see if we need to wait for more data.
	 */

	uint8_t write_count;

	if (queue_peek_units(config->consumer.queue, &write_count, 2, 1) == 1
		&& (write_count + 4) > queue_count(config->consumer.queue)) {
		/*
		 * Feed me more data, please.
		 * Reuse the buffer in usb_i2c_config to send ACK packet.
		 */
		config->buffer[0] = USB_I2C_SUCCESS;
		config->buffer[1] = 0;
		usb_i2c_write_packet(config, 4);
		return 0;
	}
	return 1;
}

void usb_i2c_execute(struct usb_i2c_config const *config)
{
	/* Payload is ready to execute. */
	uint8_t count       = usb_i2c_read_packet(config);
	int portindex       = (config->buffer[0] >> 0) & 0xff;
	/* Convert 7-bit slave address to chromium EC 8-bit address. */
	uint8_t slave_addr  = (config->buffer[0] >> 7) & 0xfe;
	int write_count     = (config->buffer[1] >> 0) & 0xff;
	int read_count      = (config->buffer[1] >> 8) & 0xff;
	int offset          = 0;    /* Offset for extended reading header. */
	int port;

	config->buffer[0] = 0;
	config->buffer[1] = 0;

	if (read_count & 0x80) {
		read_count = ((config->buffer[2] & 0xff) << 7) |
			(read_count & 0x7f);
		offset = 2;
	}

	if (!count || (!read_count && !write_count))
		return;

	if (!usb_i2c_board_is_enabled()) {
		config->buffer[0] = USB_I2C_DISABLED;
	} else if (write_count > CONFIG_USB_I2C_MAX_WRITE_COUNT ||
		write_count != (count - 4 - offset)) {
		config->buffer[0] = USB_I2C_WRITE_COUNT_INVALID;
	} else if (read_count > CONFIG_USB_I2C_MAX_READ_COUNT) {
		config->buffer[0] = USB_I2C_READ_COUNT_INVALID;
	} else if (portindex >= i2c_ports_used) {
		config->buffer[0] = USB_I2C_PORT_INVALID;
	} else {
		/*
		 * TODO (crbug.com/750397): Add security.  This currently
		 * blindly passes through ALL I2C commands on any bus the EC
		 * knows about.  It should behave closer to
		 * EC_CMD_I2C_PASSTHRU, which can protect ports and ranges.
		 */
		port = i2c_ports[portindex].port;
		config->buffer[0] = usb_i2c_map_error(
			i2c_xfer(port, slave_addr,
				 (uint8_t *)(config->buffer + 2) + offset,
				 write_count,
				 (uint8_t *)(config->buffer + 2),
				 read_count, I2C_XFER_SINGLE));
	}
	usb_i2c_write_packet(config, read_count + 4);
}

void usb_i2c_deferred(struct usb_i2c_config const *config)
{
	/* Check if we can proceed the queue. */
	if (usb_i2c_executable(config))
		usb_i2c_execute(config);
}

static void usb_i2c_written(struct consumer const *consumer, size_t count)
{
	struct usb_i2c_config const *config =
		DOWNCAST(consumer, struct usb_i2c_config, consumer);

	hook_call_deferred(config->deferred, 0);
}

struct consumer_ops const usb_i2c_consumer_ops = {
	.written = usb_i2c_written,
};