Probe problem when writing a I2C device driver...

Question

Hi all,

I am a newbie in writing linux device driver, forgive me if anything stupid a asked and my poor English^^
I am trying to write a driver for a touch panel, which communicate with CPU via I2C.
I tried to add a device driver into linux platform, and the register was success, I mean the driver was loaded, but the probe function didn't fired up!!

Above is partial code of the driver i wrote.

static int i2c_ts_probe(struct i2c_client *client, const struct i2c_device_id * id) {  
    /* ... */  
}

static int i2c_ts_remove(struct i2c_client *client) {  
    /* ... */  
}

static const struct i2c_device_id i2c_ts_id[] = {  
    {"Capacitive TS", 0},  
    { }  
};  
MODULE_DEVICE_TABLE(i2c, i2c_ts_id);  

static struct i2c_driver i2c_ts = {  
    .id_table = i2c_ts_id,  
    .probe = i2c_ts_probe,  
    .remove = i1c_ts_remobe,  
    .driver = {  
        .name = "i2c_ts",  
    },  
};

static int __init i2c_ts_init(void) {  
    return i2c_add_driver(&i2c_ts);  
}

static int __init i2c_ts_exit(void) {  
    return i2c_del_driver(&i2c_ts);  
}  

module_init(i2c_ts_init);
module_exit(i2c_ts_exit);

Above is partial code in platform (/kernel/arch/arm/mach-pxa/saarb.c) used for registering the i2c device.

static struct i2c_board_info i2c_board_info_ts[] = {
    {  
        .type = i2c_ts,  
        .irq = IRQ_GPIO(mfp_to_gpio(MFP_PIN_GPIO0)),  
    },  
};

static void __init saarb_init(void) {  
    ...  
    i2c_register_board_info(0, ARRAY_AND_SIZE(i2c_board_info_ts));  
    ...  
}

any suggestion and comment will be welcome, thanks^^

Answer 1

So that the linux device/driver model can probe your driver, there must be a device requesting it: this is achieved by comparing the name of the driver ("i2c_ts") and the type of the device in the i2c_board_info struct. In your case I guess the type is not equal to "i2c_ts".

So I would suggest that you use the I2C_BOARD_INFO macro to instantiate your device, as documented in Documentation/i2c/instantiating_devices.

static struct i2c_board_info i2c_board_info_ts[] = {
    {  
         I2C_BOARD_INFO("i2c_ts", 0x12),  
         .irq = IRQ_GPIO(mfp_to_gpio(MFP_PIN_GPIO0)),  
    },
};

static void __init saarb_init(void) {  
    ...  
    i2c_register_board_info(0, ARRAY_AND_SIZE(i2c_board_info_ts));  
    ... 
}

You had also not given an address to your device, and I2C_BOARD_INFO needs it. Read the datasheet of your touchscreen to know what that address is.

Finally, as suggested above, be sure that i2c_ts_id is correct. I am not sure it plays a role in the device/module association mechanism in the kernel, but I would say it's far less confusing it they all share the same name.