如何编写多个slave i2c客户端设备驱动程序?

我正在尝试为嵌入式主板开发驱动程序.该驱动程序应该为v4l2打开一个接口,并使用i2c与2个设备进行通信.司机将充当主人.

我似乎无法理解i2c_device_id数组和i2c_add_driver函数是如何工作的.我在内核源代码中阅读了文档,但它对多个从属客户端没有帮助.

>我必须有两个独立的探测功能吗?
>我必须两次拨打i2c_add_driver吗?
>如果不是,我将如何能够保存两个不同的客户端,以便能够将不同的字节发送到不同的地址.

我在这里粘贴我的代码.我试图实例化两个i2c_drivers,称为i2c_driver_add两次并单独实现i2c探测.该代码无法正常工作,告诉我foo1在第二次调用i2c_add_driver时已经注册.

我在我的dts文件中的i2c1下定义了两个块,如:

&i2c1 {

...
    foo0: foo0@00 {
        compatible = "bar,foo0";
        reg = <0x00>;
        pinctrl-names = "default";
        pinctrl-0 = <&pinctrl_ipu1_2>;
        clocks = <&clks IMX6QDL_CLK_CKO>;
        clock-names = "csi_mclk";
        DOVDD-supply = <&vgen4_reg>; /* 1.8v */
        AVDD-supply = <&vgen3_reg>;  /* 2.8v, on rev C board is VGEN3,
                        on rev B board is VGEN5 */
        DVDD-supply = <&vgen2_reg>;  /* 1.5v*/
        pwn-gpios = <&gpio1 16 1>;   /* active low: SD1_DAT0 */
        rst-gpios = <&gpio1 17 0>;   /* active high: SD1_DAT1 */
        csi_id = <0>;
        mclk = <24000000>;
        mclk_source = <0>;
    };

    foo1: foo1@02 {
        compatible = "bar, foo1";
        reg = <0x02>;
        pinctrl-names = "default";
        pinctrl-0 = <&pinctrl_ipu1_2>;
        clocks = <&clks IMX6QDL_CLK_CKO>;
        clock-names = "csi_mclk";
        DOVDD-supply = <&vgen4_reg>; /* 1.8v */
        AVDD-supply = <&vgen3_reg>;  /* 2.8v, on rev C board is VGEN3,
                        on rev B board is VGEN5 */
        DVDD-supply = <&vgen2_reg>;  /* 1.5v*/
        pwn-gpios = <&gpio1 16 1>;   /* active low: SD1_DAT0 */
        rst-gpios = <&gpio1 17 0>;   /* active high: SD1_DAT1 */
        csi_id = <0>;
        mclk = <24000000>;
        mclk_source = <0>;
    };

...

除了名字之外,两个街区完全相同.

在驱动程序文件中,我实例化了以下结构:

static const struct i2c_device_id foo_id[] = {
    {"foo0", 0},
    {"foo1", 1},
    {},
};

static struct i2c_driver foo0_i2c_driver = {
    .driver = {
        .owner = THIS_MODULE,
        .name = "foo0",
    },
    .probe = foo0_probe,
    .remove = foo0_remove,
    .id_table = foo_id,
};

static struct i2c_driver foo1_i2c_driver = {
    .driver = {
        .owner = THIS_MODULE,
        .name = "foo1",
    },
    .probe = foo1_probe,
    .remove = foo1_remove,
    .id_table = foo_id,
};

以下是我的init和exit函数:

MODULE_DEVICE_TABLE(i2c, foo_id);

static __init int foo_init(void)
{
    u8 err;

    err = i2c_add_driver(&foo0_i2c_driver);
    if (err != 0)
        pr_err("%s:driver registration failed i2c-slave0, error=%d\n",
            __func__, err);

    err = i2c_add_driver(&foo1_i2c_driver);
    if (err != 0)
        pr_err("%s:driver registration failed i2c-slave1, error=%d\n",
            __func__, err);

    return err;
}
static void __exit foo_clean(void)
{
    if((&foo0_i2c_driver) != NULL && i2c0initialized)
    {
        i2c_del_driver(&foo0_i2c_driver);
        i2c0initialized = 0;
    }
    if((&foo1_i2c_driver) != NULL && i2c1initialized)
    {
        i2c_del_driver(&foo1_i2c_driver);
        i2c1initialized = 0;
    }
}

module_init(foo_init);
module_exit(foo_clean);

以下是我的探测功能.我为两个奴隶都有两份副本.

static int foo_probe(struct i2c_client *client,
                          const struct i2c_device_id *device_id)
{
    struct pinctrl *pinctrls;
    struct device *dev = &client->dev;

    int ret = 0;

    pinctrls = devm_pinctrl_get_select_default(dev);
    if(IS_ERR(pinctrls))
    {
        dev_err(dev, "pinctrl setup failed\n");
        return PTR_ERR(pinctrls);
    }

    memset(&foo_data, 0, sizeof(foo_data));
    foo_data.sensor_clk = devm_clk_get(dev, "csi_mclk");
    if(IS_ERR(foo_data.sensor_clk))
    {
        dev_err(dev, "get mclk failed\n");
        return PTR_ERR(foo_data.sensor_clk);
    }

    ret = of_property_read_u32(dev->of_node, "mclk", &(foo_data.mclk));
    if(ret < 0)
    {
        dev_err(dev, "mclk frequency is invalid\n");
        return ret;
    }

    ret = of_property_read_u32(dev->of_node, "mclk_source",
                               (u32 *)&(foo_data.mclk_source));
    if(ret < 0)
    {
        dev_err(dev, "mclk source is invalid\n");
        return ret;
    }

    ret = of_property_read_u32(dev->of_node, "csi_id", &(foo_data.csi));
    if(ret < 0)
    {
        dev_err(dev, "csi_id invalid\n");
        return ret;
    }

    clk_prepare_enable(foo_data.sensor_clk);
    i2c_client0 = client;

    /* custom data structures are set here */   

    foo_reset();

    ret = foo_get_id();

    if(ret < 0 /* || ret != foo_ID */)
    {
        clk_disable_unprepare(foo_data.sensor_clk);
        pr_warning("foo is not found\n");
        return -ENODEV;
    }

    clk_disable_unprepare(foo_data.sensor_clk);
    foo_int_device.priv = &foo_data;
    ret = v4l2_int_device_register(&foo_int_device);

    pr_info("foo is found\n");
    i2c0initialized = 1;
    return ret;
}
最佳答案
这个答案迟到了5个月,但希望它会帮助那些遇到同样问题的人(就像我一样)并找不到合适的答案.

简而言之,解决方案是使用次要编号来表示每个从站.您的驱动程序将在您存储的客户端列表中查找该次要编号,以获取正确的i2c_client.

长版
您的I2C驱动程序最终可能是这种独特设备的字符设备驱动程序.否则,框架(例如hwmon)可能已经实现,并且框架已经完成了处理多个从属设备,因此您无需担心它.有关示例,请参见http://lxr.free-electrons.com/source/drivers/hwmon/.

现在假设它是一个字符设备驱动程序,在你的驱动程序__init中你需要分配与slave设备一样多的次要数字:

alloc_chrdev_region(&dev, *MINOR_START*, *NUM_DEVICES*, name)    
/* for each minor or slave device, do cdev_init and cdev_add */

现在进入你的MODULE_DEVICE_TABLE.输入每个从站的条目,记住该字符串必须与设备树兼容的条目匹配.第二个字段是一个数字,我们将它用作唯一标识符和次要编号(这是技巧):

struct i2c_device_id foo_idtable[] = {
    { "foo_1", 0 },
    { "foo_2", 1 },
    { },
};
MODULE_DEVICE_TABLE(i2c, foo_idtable);

好的,将为每个匹配的设备树条目调用.probe函数.调用.probe函数时,Linux会传入它为您实例化的i2c_client指针.这是技巧的另一部分,有一个存储这些单独的i2c_client指针的全局表.全局表的索引是次要编号.次要编号是传入的id-> driver_data,它是您之前在foo_idtable中指定的编号.

static int foo_probe(struct i2c_client *client, const struct i2c_device_id *id)
{
    /* Store the i2c_client pointer in a global table using minor number as index 
     * make sure to allocate the global table dynamically */
    that_table[id->driver_data] = client;
    /* The id->driver_data is the minor number! */
}

希望你现在正在追赶.
当您修改.ko时,您想要创建多个节点,每个小节点一个节点:

insmod foo.ko
make_dir /dev/foo
find_major foo
make_node /dev/foo/foo_0 c <major> 0
make_node /dev/foo/foo_1 c <major> 1

现在,当您的用户空间代码尝试使用您的驱动程序时,它将打开与正确的次要编号(从属设备)对应的文件.在用户空间中,您可以执行以下操作:

/* Accessing slave #0 */
int fd = open("/dev/foo/foo_0", O_RDWR);

/* Accessing slave #1 */
int fd_1 = open("/dev/foo/foo_1", O_RDWR);

您的.open实现将被调用.

static int foo_driver_open(struct inode *inode, struct file *filep)
{
    int minor_num = MINOR(inode->i_rdev);
    /* remember the global table we had before that was indexed using the minor number?
     * Let's get the i2c_client stored there and get filep->private_data
     * to point to that i2c_client. Then subsequent read/write/ioctl can just
     * obtain the i2c_client from filep->private_data */
    filep->private_data = that_table[minor_num];
}

然后,例如,您的用户空间代码调用驱动程序的ioctl:

ioctl(fd, FOO_IOCTL_DO_READ, &msg);
ioctl(fd_1, FOO_IOCTL_DO_WRITE, &msg);

在你的驱动程序的ioctl实现中:

long foo_driver_ioctl(struct file *filep, unsinged int cmd, unsigned long arg)
{
    /* the filep->private_data has the i2c_client pointer! yay! */
    struct i2c_client *client = filep->private_data;

    /* now you can talk to your slave device with the i2c_client knowing
     * it is the correct i2c_client */
}

而已 :).
我希望这是有道理的.这是一个很长的解释,但我希望我是彻底的,但不是太混乱.最大的问题是我们有一个存储i2c_cient指针的全局表,但由于.probe和.open没有办法在彼此之间传递参数,所以我想不出一种方法.如果有人有更好的解决方案,请告诉我.

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