On Fri, Nov 2, 2018 at 4:16 PM Arnd Bergmann [off-list ref] wrote:

asus_wmi_evaluate_method() is an empty dummy function when CONFIG_ASUS_WMI
is disabled, or not reachable from a built-in device driver. This leads to
a theoretical evaluation of an uninitialized variable that the compiler
complains about, failing to check that the hardcoded return value makes
this an unreachable code path:

In file included from include/linux/printk.h:336,
                 from include/linux/kernel.h:14,
                 from include/linux/list.h:9,
                 from include/linux/dmi.h:5,
                 from drivers/hid/hid-asus.c:29:
drivers/hid/hid-asus.c: In function 'asus_input_configured':
include/linux/dynamic_debug.h:135:3: error: 'value' may be used uninitialized in this function [-Werror=maybe-uninitialized]
   __dynamic_dev_dbg(&descriptor, dev, fmt, \
   ^~~~~~~~~~~~~~~~~
drivers/hid/hid-asus.c:359:6: note: 'value' was declared here
  u32 value;
      ^~~~~

With an extra IS_ENABLED() check, the warning goes away.

Fixes: 3b692c55e58d ("HID: asus: only support backlight when it's not driven by WMI")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds