如何写多个slave i2c client device driver?

How to write multiple slave i2c client device driver?

我正在尝试为嵌入式板开发 driver。 driver 应该为 v4l2 打开一个接口,并使用 i2c 与 2 个设备通信。 driver 将充当主人。

我似乎无法理解 i2c_device_id 数组和 i2c_add_driver 函数的工作原理。我阅读了内核源代码中的文档,但它对多个从属客户端没有帮助。

我在这里粘贴我的代码。我尝试实例化两个 i2c_drivers,调用 i2c_driver_add 两次并分别实现 i2c 探针。当它第二次调用 i2c_add_driver 时,代码无法告诉我 foo1 已经注册。

我在我的 dts 文件中的 i2c1 下定义了两个块,例如:

&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>;
    };

...

两个方块完全一样,只是名字不同。

在 driver 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,
};

下面是我的 initexit 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);

下面是我的 probe 函数。我为两个奴隶准备了两份。

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;
}

这是我现在正在使用的解决方法,我不会接受这个作为答案,因为这个方法感觉不对。

struct i2c_client *foo_i2c_client;

static int foo_probe(struct i2c_client *client,
                          const struct i2c_device_id *device_id)
{
    foo_i2c_client = client;
    // implementation
}

static int foo_remove(struct i2c_client *client)
{
    // implementation
}

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

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

static int send_cmd(u8 slv_addr, u8 *buffer, u16 size)
{
    foo_i2c_client->address = slv_addr;
    i2c_master_send(foo_i2c_client, buffer, size);
    // rest of implementation
} 

MODULE_DEVICE_TABLE(i2c, foo_id);

module_i2c_driver(foo0_i2c_driver);

这个答案晚了 5 个月,但希望它能帮助遇到同样问题(和我一样)但找不到 suitable 答案的其他人。

总之解决办法就是用一个minor number来代表每个slave。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得正确的 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站的工作,因此您不必担心。有关示例,请参阅 http://lxr.free-electrons.com/source/drivers/hwmon/

现在假设它是一个字符设备驱动程序,在您的驱动程序中__init您需要分配与从属设备一样多的次设备号:

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

现在开始 MODULE_DEVICE_TABLE。为每个从站输入条目,记住字符串必须与设备树兼容条目相匹配。第二个字段是一个数字,我们将把它用作唯一标识符和次要数字(这就是诀窍):

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

好的,您的 .probe 函数将为每个匹配的 device-tree 条目调用。当调用 .probe 函数时,Linux 传入它为您实例化的 i2c_client 指针。这是技巧的另一部分,有一个全局 table 存储这些单独的 i2c_client 指针。 global table 的index是minor number。 minor number就是同样传入的id->driver_data,就是你之前在foo_idtable中分配的号码

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! */
}

希望你现在赶上了。 当你 insmod 你的 .ko 时,你想要制作多个节点,每个节点一个次要编号:

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)相对应的文件。在用户空间你会做这样的事情:

/* 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);

在您的驱动程序的 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 */
}

就是这样:)。 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,但不要太混乱。最大的问题是我们有一个全局的 table 存储 i2c_cient 指针,但我想不出没有它的方法,因为 .probe.open 有没有办法在彼此之间传递参数。如果有人有更好的解决方案,请告诉我。