With regards to Linux device drivers, my understanding (obtained from reading this excellent DIY article) is that there are essentially six events/parts of a device driver "lifecycle":
Load
- the compiled driver is loaded as a Linux kernel module via insmod
Open
- the device is opened/readied for usageRead
/Write
- the device is usedClose
- the device is closed/disconnected, currently no longer useable (unless re-opened)Release
- the driver (now a kernel module) is unloaded from the kernel via rmmod
Thanks to that article and countless others, I can now write a whole bunch of C code to implement hooks/callbacks for what should happen when the kernel issues Open
, Read
, Write
and Close
commands. But, it seems that the driver must be loaded/released manually by issuing an insmod
(load) and rmmod
(release) at the shell.
However, I know this can't be the case because certain devices, like USB, allow you to connect/disconnect them dynamically/on-the-fly, and their respective drivers must be automatically loaded/released on-the-fly as well.
So this stirs up the following question: How do certain technologies, like USB, automate the execution of insmod
and rmmod
(hence the dynamic loading/releasing of USB device drivers)?
Its based on linux hotplug. The below link may useful for you.
https://web.archive.org/web/20150316211806/http://www.makelinux.net/ldd3/chp-14-sect-7