OpenCellular/include/usb_i2c.h

/* 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 "consumer.h"
#include "producer.h"
#include "registers.h"
#include "task.h"
#include "usb_descriptor.h"
#include "util.h"

#ifndef __CROS_USB_I2C_H
#define __CROS_USB_I2C_H

/*
 * Command:
 *     +----------+-----------+---------------+---------------+---------------+
 *     | port: 1B | addr: 1B  | wr count : 1B | rd count : 1B | data : <= 60B |
 *     +----------+-----------+---------------+---------------+---------------+
 *
 *     port address:  1 byte, i2c interface index
 *
 *     slave address: 1 byte, i2c 7-bit bus address
 *
 *     write count:   1 byte, zero based count of bytes to write
 *
 *     read count:    1 byte, zero based count of bytes to read
 *
 *     data:          write payload up to 60 bytes of data to write,
 *                    length must match write count
 *
 * Response:
 *     +-------------+---+---+-----------------------+
 *     | status : 2B | 0 | 0 | read payload : <= 60B |
 *     +-------------+---+---+-----------------------+
 *
 *     status: 2 byte status
 *         0x0000: Success
 *         0x0001: I2C timeout
 *         0x0002: Busy, try again
 *             This can happen if someone else has acquired the shared memory
 *             buffer that the I2C driver uses as /dev/null
 *         0x0003: Write count invalid (> 60 bytes, or mismatch with payload)
 *         0x0004: Read count invalid (> 60 bytes)
 *         0x0005: The port specified is invalid.
 *         0x8000: Unknown error mask
 *             The bottom 15 bits will contain the bottom 15 bits from the EC
 *             error code.
 *
 *     read payload: up to 60 bytes of data read from I2C, length will match
 *                   requested read count
 */

enum usb_i2c_error {
	USB_I2C_SUCCESS             = 0x0000,
	USB_I2C_TIMEOUT             = 0x0001,
	USB_I2C_BUSY                = 0x0002,
	USB_I2C_WRITE_COUNT_INVALID = 0x0003,
	USB_I2C_READ_COUNT_INVALID  = 0x0004,
	USB_I2C_PORT_INVALID        = 0x0005,
	USB_I2C_UNKNOWN_ERROR       = 0x8000,
};


#define USB_I2C_MAX_WRITE_COUNT 60
#define USB_I2C_MAX_READ_COUNT  60

BUILD_ASSERT(USB_MAX_PACKET_SIZE == (1 + 1 + 1 + 1 + USB_I2C_MAX_WRITE_COUNT));
BUILD_ASSERT(USB_MAX_PACKET_SIZE == (2 + 1 + 1 + USB_I2C_MAX_READ_COUNT));

/*
 * Compile time Per-USB gpio configuration stored in flash.  Instances of this
 * structure are provided by the user of the USB i2c.  This structure binds
 * together all information required to operate a USB i2c.
 */
struct usb_i2c_config {
	uint16_t *buffer;

	/* Deferred function to call to handle SPI request. */
	const struct deferred_data *deferred;

	struct consumer const consumer;
	struct queue const *tx_queue;
};

extern struct consumer_ops const usb_i2c_consumer_ops;

/*
 * Convenience macro for defining a USB I2C bridge driver.
 *
 * NAME is used to construct the names of the trampoline functions and the
 * usb_i2c_config struct, the latter is just called NAME.
 *
 * INTERFACE is the index of the USB interface to associate with this
 * I2C driver.
 *
 * INTERFACE_NAME is the index of the USB string descriptor (iInterface).
 *
 * ENDPOINT is the index of the USB bulk endpoint used for receiving and
 * transmitting bytes.
 */
#define USB_I2C_CONFIG(NAME,						\
		       INTERFACE,					\
		       INTERFACE_NAME,					\
		       ENDPOINT)					\
	static uint16_t							\
		CONCAT2(NAME, _buffer_)[USB_MAX_PACKET_SIZE/2];		\
	static void CONCAT2(NAME, _deferred_)(void);			\
	DECLARE_DEFERRED(CONCAT2(NAME, _deferred_));			\
	static struct queue const CONCAT2(NAME, _to_usb_);		\
	static struct queue const CONCAT3(usb_to_, NAME, _);		\
	USB_STREAM_CONFIG_FULL(CONCAT2(NAME, _usb_),			\
			       INTERFACE,				\
			       USB_CLASS_VENDOR_SPEC,			\
			       USB_SUBCLASS_GOOGLE_I2C,			\
			       USB_PROTOCOL_GOOGLE_I2C,			\
			       INTERFACE_NAME,				\
			       ENDPOINT,				\
			       USB_MAX_PACKET_SIZE,			\
			       USB_MAX_PACKET_SIZE,			\
			       CONCAT3(usb_to_, NAME, _),		\
			       CONCAT2(NAME, _to_usb_))			\
	struct usb_i2c_config const NAME = {				\
		.buffer    = CONCAT2(NAME, _buffer_),			\
		.deferred  = &CONCAT2(NAME, _deferred__data),		\
		.consumer  = {						\
			.queue = &CONCAT3(usb_to_, NAME, _),		\
			.ops   = &usb_i2c_consumer_ops,			\
		},							\
		.tx_queue = &CONCAT2(NAME, _to_usb_),			\
	};								\
	static struct queue const CONCAT2(NAME, _to_usb_) =		\
		QUEUE_DIRECT(USB_MAX_PACKET_SIZE, uint8_t,		\
		null_producer, CONCAT2(NAME, _usb_).consumer);		\
	static struct queue const CONCAT3(usb_to_, NAME, _) =		\
		QUEUE_DIRECT(USB_MAX_PACKET_SIZE, uint8_t,		\
		CONCAT2(NAME, _usb_).producer, NAME.consumer);		\
	static void CONCAT2(NAME, _deferred_)(void)			\
	{ usb_i2c_deferred(&NAME); }

/*
 * Handle I2C request in a deferred callback.
 */
void usb_i2c_deferred(struct usb_i2c_config const *config);

/*
 * These functions should be implemented by the board to provide any board
 * specific operations required to enable or disable access to the I2C device.
 */
int usb_i2c_board_enable(void);
void usb_i2c_board_disable(void);
#endif  /* __CROS_USB_I2C_H */