uboot i2c 操作函式記錄

• I2C 在 u-boot 上面，有直接操作 I2C 的函式

  // drivers/i2c/i2c_core.c
  
  // 設定在哪個 I2C bus 上工作
  276 int i2c_set_bus_num(unsigned int bus)
  277 {
  278     int max;
  279
  280     if ((bus == I2C_BUS) && (I2C_ADAP->init_done > 0))
  281         return 0;
  282
  283 #ifndef CONFIG_SYS_I2C_DIRECT_BUS
  284     if (bus >= CONFIG_SYS_NUM_I2C_BUSES)
  285         return -1;
  286 #endif
  287
  288     max = ll_entry_count(struct i2c_adapter, i2c);
  289     if (I2C_ADAPTER(bus) >= max) {
  290         printf("Error, wrong i2c adapter %d max %d possible\n",
  291                I2C_ADAPTER(bus), max);
  292         return -2;
  293     }
  294
  295 #ifndef CONFIG_SYS_I2C_DIRECT_BUS
  296     i2c_mux_disconnect_all();
  297 #endif
  298
  299     gd->cur_i2c_bus = bus;
  300     if (I2C_ADAP->init_done == 0)
  301         i2c_init_bus(bus, I2C_ADAP->speed, I2C_ADAP->slaveaddr);
  302
  303 #ifndef CONFIG_SYS_I2C_DIRECT_BUS
  304     i2c_mux_set_all();
  305 #endif
  306     return 0;
  307 }    
  //etc     i2c_set_bus_num(1);
  
  //  i2c slave 匹配
  313 int i2c_probe(uint8_t chip)
  314 {
  315     return I2C_ADAP->probe(I2C_ADAP, chip);
  316 }
  // etc  i2c_probe(0x68)
  //  返回是否成功， 0 表示成功 ， 非 0 表示失敗
  
  // i2c  讀寫 寫
  330 int i2c_read(uint8_t chip, unsigned int addr, int alen,
  331                 uint8_t *buffer, int len)
  332 {
  333     return I2C_ADAP->read(I2C_ADAP, chip, addr, alen, buffer, len);
  334 }
  335
  336 int i2c_write(uint8_t chip, unsigned int addr, int alen,
  337                 uint8_t *buffer, int len)
  338 {
  339     return I2C_ADAP->write(I2C_ADAP, chip, addr, alen, buffer, len);
  340 }
  
  //etc 
              uchar wri_data = 0x3f, red_data;
   90     if (i2c_write(0x68, 1, 1, (uchar *)&wri_data, sizeof(int)))
   91         puts("write error\n");
   92
   93     if (i2c_read(0x68, 1, 1, (uchar *)&red_data,
   94              sizeof(int))) {
   95         puts("Could not read the MCU; something fundamentally"
   96             " wrong on the I2C bus.\n");
   97         return -EIO;
   98     }