The devstat API expects us to reuse one devinfo for many invocations of
devstat_getstats. In particular, it allocates and resizes memory
referenced by devinfo.
Querying the number of devices separately from the device list itself is
racy. Devices may be added or removed between the two calls; and removed
devices would lead to a segfault.
The memory allocated by calloc was never freed. Since the devinfo struct
never leaves the function, anyway, we might as well just allocate it on
the stack.
Karsten Weiss
Juergen Hoetzel
Dominik Honnef
Johannes 'fish' Ziemke
Matthias Rampke
Siavash Safi