> then I went to my linux directory, and I ran:
> 
> spatch --linux-spacing --include-headers --in-place -sp_file ~/misc/wet-ul_l.cocci drivers/i2c/busses
> 
> and all worked as it should (diff output plus the same output from git
> diff).

I took your same spatch and ran the same commandline and got no output
but still the same sys_error. I have a train travel ahead of me. I'll
try to find out what is so different on my system. For the record, I run
Debian testing, but the sys_error was there for a long time for me.
Alyways Debian, though. And mostly coccinelle from Debian. I just
switched to the top-of-head self-compiled version.