Question

How does probe() call gets called? Who calls it? As per my understanding, __init() registers driver and then somehow probe() is called to register the device data and irq etc. How exactly it happens?

I am working on touchscreen driver and its __init registers itself to i2c driver. Then probe expect i2c_client data which returns null. I want to track where it gets filled.

Answer 1

Long story short: the probe() function of the driver is called as a result of calling the register_driver for that specific bus. More precisely, it’s called by the probe() of that bus_type structure. In your case: i2c_bus_type.

Here’s the call chain in your I2C case:

• i2c_register_driver
• driver_register
• bus_add_driver
• driver_attach
• __driver_attach (for your device)
• driver_probe_device
• really_probe
• i2c_device_probe (this is what dev->bus->probe is for an i2c driver)
• your_probe_function