origin: https://blog.csdn.net/mcgrady_tracy/article/details/51288138
2016年04月30日 22:13:14
阅读数:5817
i2c_register_board_info()函数用于往__i2c_board_list这条链表添加一条i2c设备信息,在i2c adapter注册的时候,会扫描__i2c_board_list链表,然后调用i2c_new_device()函数来注册i2c设备,注意,要先于i2c adapter注册之前就添加好i2c设备信息,否则会出现调用了i2c_register_board_info()函数,而设备不能注册的情况。
i2c_register_board_info()函数如下:
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int __init
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i2c_register_board_info(int busnum,
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struct i2c_board_info const *info, unsigned len)
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{
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int status;
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down_write(&__i2c_board_lock);
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/* dynamic bus numbers will be assigned after the last static one */
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if (busnum >= __i2c_first_dynamic_bus_num)
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__i2c_first_dynamic_bus_num = busnum + 1;
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for (status = 0; len; len--, info++) {
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struct i2c_devinfo *devinfo;
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devinfo = kzalloc(sizeof(*devinfo), GFP_KERNEL);
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if (!devinfo) {
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pr_debug("i2c-core: can't register boardinfo!\n");
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status = -ENOMEM;
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break;
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}
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devinfo->busnum = busnum;
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devinfo->board_info = *info;
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list_add_tail(&devinfo->list, &__i2c_board_list);
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}
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up_write(&__i2c_board_lock);
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return status;
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}
注册i2c总线流程如下:
i2c_add_numbered_adapter()->i2c_register_adapter()
在i2c_register_adapter()函数中调用了i2c_scan_static_board_info()函数,代码如下:
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static void i2c_scan_static_board_info(struct i2c_adapter *adapter)
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{
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struct i2c_devinfo *devinfo;
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down_read(&__i2c_board_lock);
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list_for_each_entry(devinfo, &__i2c_board_list, list) {
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if (devinfo->busnum == adapter->nr
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&& !i2c_new_device(adapter,
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&devinfo->board_info))
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dev_err(&adapter->dev,
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"Can't create device at 0x%02x\n",
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devinfo->board_info.addr);
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}
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up_read(&__i2c_board_lock);
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}
i2c_scan_static_board_info()函数先扫描__i2c_board_list,然后调用i2c_new_device()函数来注册i2c设备。这就是静态注册i2c设备的方法,一般在板级的初始化函数中调用i2c_register_board_info()函数来完成i2c设备信息的添加。
除了这种方法外,Linux还提供了另外的方法来注册i2c设备。例如:
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static const unsigned short normal_i2c[] = { 0x2c, 0x2d, I2C_CLIENT_END };
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static int __devinit usb_hcd_pnx4008_probe(struct platform_device *pdev)
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{
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(...)
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struct i2c_adapter *i2c_adap;
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struct i2c_board_info i2c_info;
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(...)
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i2c_adap = i2c_get_adapter(2);
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memset(&i2c_info, 0, sizeof(struct i2c_board_info));
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strlcpy(i2c_info.name, "isp1301_pnx", I2C_NAME_SIZE);
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isp1301_i2c_client = i2c_new_probed_device(i2c_adap, &i2c_info,
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normal_i2c);
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i2c_put_adapter(i2c_adap);
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(...)
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}
来自Documentation/i2c/instantiating-devices。
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