i2c - gpio

处理器只支持3个i2c通道，常常会不够用，最近写了一个gpio模拟i2c的driver，把模拟的i2c通道加入了i2c-core中，作为第 4 通道，调用接口与标准i2c一致，代码如下：
[cpp]
#define DELAY     2
#define SCL_GPIO GPIO_I2C_SCL
#define SDA_GPIO GPIO_I2C_SDA

static inline void i2c_delay(uint16_t delay)
{
    udelay(delay);
}

static inline void set_scl_low(void)
{
    gpio_direction_output(SCL_GPIO, 0);
}

static inline void set_scl_high(void)
{
    gpio_direction_output(SCL_GPIO, 1);
}

static inline void set_sda_low(void)
{
    gpio_direction_output(SDA_GPIO, 0);
}

static inline void set_sda_high(void)
{
    gpio_direction_output(SDA_GPIO, 1);
}

static inline void set_sda_in(void)
{
    gpio_direction_input(SDA_GPIO);
}

static inline uint8_t get_sda_bit(void)
{
    return __gpio_get_value(SDA_GPIO);
}

int i2c_gpio_init(void)
{
    int err;
    err = gpio_request(SCL_GPIO, NULL);
    if (err != 0)
        return err;
    err = gpio_request(SDA_GPIO, NULL);

    set_sda_high();
    set_scl_high();

    return err;
}

void i2c_gpio_free(void)
{
    gpio_free(SDA_GPIO);
    gpio_free(SCL_GPIO);
}

static inline void i2c_start(void)
{
    set_sda_high();
    i2c_delay(DELAY);
    set_scl_high();
    i2c_delay(DELAY);

    set_sda_low();
    i2c_delay(DELAY);
    set_scl_low();
    i2c_delay(DELAY);
}

static inline void i2c_stop(void)
{
    set_sda_low();
    i2c_delay(DELAY);
    set_scl_high();
    i2c_delay(4*DELAY);
    set_sda_high();
    i2c_delay(4*DELAY);
}

/*
* return value:
*      0 --- 收到ACK
*      1 --- 没收到ACK
*/
uint8_t i2c_send_byte(uint8_t send_byte)
{
    uint8_t rc = 0;
    uint8_t out_mask = 0x80;
    uint8_t count = 8;
    uint8_t value;

    while(count > 0) {
        set_scl_low();
        i2c_delay(DELAY);
        value = ((send_byte & out_mask) ? 1 : 0);
        if(value == 1) {
            set_sda_high();
        } else {
            set_sda_low();
        }
        send_byte <<= 1;
        i2c_delay(DELAY);

        set_scl_high();
        i2c_delay(DELAY);

        count--;
    }
    set_scl_low();
    set_sda_in();
    i2c_delay(4*DELAY);
    set_scl_high();
    i2c_delay(DELAY);
    rc = get_sda_bit();
    i2c_delay(DELAY);
    set_scl_low();

    return rc;
}

/*
* ack = 0 发送ACK
* ack = 1 发送非ACK停止读取
*/
void i2c_read_byte(uint8_t *buffer, uint8_t ack)
{
    uint8_t count = 0x08;
    uint8_t data = 0x00;
    uint8_t temp = 0;

    while(count > 0) {
        set_scl_low();
        i2c_delay(2*DELAY);
        if(count == 8)
            set_sda_in();
        i2c_delay(DELAY);
        set_scl_high();
        i2c_delay(2*DELAY);
        temp = get_sda_bit();
        data <<= 1;
        if(temp)
            data |= 0x01;

        i2c_delay(DELAY);
        count--;
    }

    set_scl_low();
    i2c_delay(2*DELAY);
    if(ack) {
        set_sda_high();
    } else {
        set_sda_low();
    }
    i2c_delay(DELAY);
    set_scl_high();
    i2c_delay(2*DELAY);

    *buffer = data;
    set_scl_low();
}

struct atxx_i2c_gpio {
    struct i2c_adapter adap;
    struct device *dev;
    struct clk *clk;
    struct i2c_msg *msg;
    spinlock_t lock;
};

static int send_i2c(struct atxx_i2c_gpio *i2c)
{
    int i;
    uint8_t ack;

    spin_lock_irq(&i2c->lock);
    i2c_start();

    ack = i2c_send_byte((i2c->msg->addr << 1) | 0x00);
    if(ack){
        goto out;
    }

    for(i = 0; i < i2c->msg->len; i++) {&

补充：软件开发 , C++ ,