Detect the presence of a device when it's hot plugged in Linux

Question

I am running the SPI code on the panda board and I want to know which function in the code is responsible for detecting the device when it's hot plugged.

Can somebody with the background of embedded systems, Linux device drivers and/or spi please answer my question?

Bully

Answer 1

This is the line in your code that does the magic:

1286 MODULE_DEVICE_TABLE(of, omap_mcspi_of_match);

Process:
1. Driver for each device exposes its information using the API MODULE_DEVICE_TABLE. Each device has a unique vendor Id and device Id.
2. At compilation time, the build process extracts this information out of the driver and builds a table.
3. When the device is plugged in, the kernel checks this device table to see if any driver is available for the particular Vendor/Device Id. If yes then it loads that driver and initializes the device.

---

Read following articles for more info:

1. http://www.linux-mag.com/id/2617/
2. http://www.linuxjournal.com/node/5604/print

Steve

can you please explain the structure members of of_device_id I searched online, but I couldn't find the explanation. – Bully

Especially explanation of the member .data – Bully

Read the 2nd link, it's explained under Preprocessor Abuse . – Steve

Is it called device table? I'm trying to query on google linux print device table (e.g. to determine whether there is a driver for given product, vendor IDs), but see nothing relevant. – Indemonstrable

Nevermind, I found here that I can look it up in the file /lib/modules/$(uname -r)/modules.alias. I don't quite understand though what is the relation between the file and your device table. – Indemonstrable

the links provided are no longer valid :( – Linton

@Linton Here are working links web.archive.org/web/20141216112516/http://www.linux-mag.com/id/… and web.archive.org/web/20161108061014/http://www.linuxjournal.com/… -- I tried to amend the answer, but the edit queue was full already. – Dispense

@Steve - does the struct pci_device_id my_pci_tbl that I define and add to the MODULE_DEVICE_TABLE(pci, my_pci_tbl);` ALSO HAS to be set in the (PCI in this case) id_table of the `struct pci_driver pchar_driver = { .name = "my pci device", .id_table = my_pci_tbl, .probe = my_probe_function, remove = my_remove_function,} – Twotime