USB reverse engineering: down the rabbit hole

I tend to dive down rabbit holes a lot, and given the cost of context switching and memory deteriorating over time, sometimes the state I build up in my mind gets lost between the chances I get to dive in. These 'linkdump' posts are an attempt to collate at least some of that state in a way that I can hopefully restore to my brain at a later point.This time around I was inspired to look into USB reverse engineering, protocol analyis, hardware hacking, and what would be involved in implementing custom drivers for arbitrary hardware. Or put another way: how do I hack all of the USBs?!??It seems the deeper I went, the more interesting I found the content, and this post grew and grew. Hopefully it will help to shortcut your own journey down this path, and enlighten you to a whole new area of interesting things to hack!

Let's continue this impromptu series on things I barely understand, shall we?