Hi Dmitry,

Replacing BUG() with WARN_ON() + return is the right call, and the rest of
the patch is fine.

One nit on the changelog though: this guard isn't reachable from userspace.
reg and len are always driver-internal constants -- there is no sysfs/debugfs/
ioctl that lets userspace pick a register, every __mms114_read_reg() call site
passes a fixed reg >= MMS114_INFORMATION (0x10), and the single MMS114_MODE_CONTROL
read is short-circuited by the cache in mms114_read_reg() before it ever reaches
__mms114_read_reg(). So the condition only fires if a *future in-kernel caller*
requests a read that spans the write-only MODE_CONTROL register -- a driver-
internal invariant, not a userspace-triggered one.

Worth tightening the wording, since that distinction is exactly what justifies
WARN_ON() here: a genuinely userspace-reachable WARN_ON() would itself be a
problem (log spam / panic_on_warn). Maybe something like:

  "Avoid taking the machine down with BUG() if a caller ever requests a read
   spanning the write-only MODE_CONTROL register; warn and return -EINVAL so
   the driver can recover."

The code is good either way.

Thanks,
Bryam