I have a USB lamp,which just switches on when plugged into a USB port. I connected it to my computer and ran lsusb, but could not find the device. How does the OS handle these devices? Are the USB power pins always powered with 5V, or does it get powered when the OS detects a device? If the OS detects a device and then supplies power to the USB slot, how do I locate the drivers associated with the device?
The device is something similar to the device listed here: https://www.amazon.in/Codered-Portable-Flexible-Light-Colors/dp/B078N9DQ8B
From the image and description below, the product in question looks like a "dumb" device to me. By dumb i mean it only uses the +5V and GND lines from the USB connector. The D+/D- used to communicate are not connected and therefore no drivers are required/applicable. Given USB is a fairly complex and comprehensive protocol, you could probably pick up a copy of USB Complete: the first few chapters should get you started in the right direction. I have also found this helpful.
BTW, external links (esp amazon products) tend to die, so upload and include a picture (when you have the reputation points) otherwise the context of the question can be lost.