So was going through the Linux kernel

we can only hope we don't ever go there

Why do a default: break; then? You can leave it out.

Oh cool.

I have similar parts in my code and thought was bad.

Good to see others do it to :D
(in my case I often write logs in that case "we should have ended up here.."

@filthyranter So that there's a place to put the comment.

Mhm Interesting.
10 years Linux, never went that far.

@filthyranter
It's a pattern of "good programming" to include the default case.
This makes it clear that
a) there could be a different case that handled above.
B) the programmer is aware of this task and c) may have taken proper action

So for general: increase readability, decrease misunderstanding and error rate. Create more 'fool proof systems' (at least in my opinion, you can Ofc say 'more code decreases the readability - it's a guideline not a rule)

@Daniil I'd make a comment

/* default case not needed */

@filthyranter
In my opinion would be the same or equivalent.

Though " default " can be checked by tools your comment not (or not that easy).