rk3188 i2c错误"set master error"

定位错误打印是在i2c-rk30-adapter.c的rk30_i2c_set_master()中。 发现是msgs[0].len > 3就返回报错，可能是控制器buffer不够大，所以要做限制，项目赶时间，没有细看文档。

解决办法：

将数据拆分读/写。

int sample = writelen / 3;

int remain = writelen % 3;
int i;

for (i = 0; i < sample; i++) {
     struct i2c_msg msgs[] = {
          {
               .addr = client->addr,
               .flags = 0,
               .len = 3,
               .buf = &writebuf[i * 3],
               .scl_rate = I2C_SPEED,
          },
     };
     ret = i2c_transfer(client->adapter, msgs, 1);
     if (ret < 0)
          dev_err(&client->dev, "%s: i2c read error.\n", __func__);
}

if (remain) {
     struct i2c_msg msgs[] = {
          {
               .addr = client->addr,
               .flags = 0,
               .len = remain,
               .buf = &writebuf[i * 3],
               .scl_rate = I2C_SPEED,
          },
     };
     ret = i2c_transfer(client->adapter, msgs, 1);
     if (ret < 0)
          dev_err(&client->dev, "%s: i2c read error.\n", __func__);

}