The kernel determines whether peripherals are attached to the I2C address

Record a way to judge i2c Whether peripherals are attached to the address .
Use scenarios , Both drivers use the same reset pin and interrupt pin , Use the same peripheral interface , It is not allowed to use at the same time , Just mounted i2c Different addresses , The idea is to read the value of this register when registering the driver , The return value is used to determine whether there is a cause peripheral .

One 、 Code changes

dits To configure

i2c4{
    
	[email protected]2a {
    
		reg = <0x2a>;
		compatible = "eeti,egalax_i2c";
		interrupt-parent = <&gpio4>;
		interrupts = <13 2>;
		int-gpios = <&gpio4 13 0>;
		reset-gpios = <&gpio4 12 0>;
	};

	[email protected]5d {
    
		compatible = "goodix,gt928_ts";
		reg = <0x5d>;
		irq-gpios = <&gpio4 13 0>;
		reset-gpios = <&gpio4 12 0>;
	};
};

Then the corresponding peobe Add the following judgment to the function ：
The function used is i2c_smbus Read interface of ：

	/* Correlation function again  kernel Of  inlcude/linux/i2c.h in  *s32 i2c_smbus_read_byte_data(const struct i2c_client *client, u8 command); *const struct i2c_client *client  It's designated by your peripheral i2c Bus  *u8 command 8 Bit address  */
	/*vol Is the return value , If it doesn't exist, then it returns a negative number */
	/* Before using this function, you need to set client The value of is given first so that it can pass I2C Interface function to read */
    vol = i2c_smbus_read_byte_data(p_egalax_i2c_dev->client,  p_egalax_i2c_dev->client->addr);
    if (vol < 0) {
    
   		printk("cluo---> vol 0x%x = %d", client->addr, vol);	
        return -ENODEV;
	}

By inserting different peripherals , You can see different printing information .

[    3.430773] cluo---> vol 0x2a = -6
[    3.434279] cluo---> eglax_tp probe error
[    4.542063] cluo---> vol 0x5d = 0
[    4.596902] cluo---> goodix probe success

[    3.448004] cluo---> nret 0x2a = -6
[    3.451509] cluo---> eglax_tp probe error
[    4.571818] cluo---> vol 0x5d = -6
[    4.575928] cluo---> goodix probe error

[    3.455065] cluo---> nret 0x2a = 2
[    3.466904] cluo---> egalax probe success
[    4.592851] cluo---> vol 0x5d = -6
[    4.596902] cluo---> goodix probe error

Two 、 Realization principle

Because drivers can be loaded successfully alone , The purpose is to avoid driving to the right gpio To operate , Because they all use the same gpio, So we can't let them drive the right gpio To apply for , Because once you apply, it will lead to ningwai gpio You can't be right gpio To operate . So you need to add this judgment function gpio Before applying .