[PATCH] HID: asus: fix build warning wiht CONFIG_ASUS_WMI disabled

[PATCH] HID: asus: fix build warning wiht CONFIG_ASUS_WMI disabled

[Arnd Bergmann]

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>
---
 drivers/hid/hid-asus.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/hid/hid-asus.c b/drivers/hid/hid-asus.c
index dc6d6477e961..a1fa2fc8c9b5 100644
--- a/drivers/hid/hid-asus.c
+++ b/drivers/hid/hid-asus.c
@@ -359,6 +359,9 @@ static bool asus_kbd_wmi_led_control_present(struct hid_device *hdev)
 	u32 value;
 	int ret;
 
+	if (!IS_ENABLED(CONFIG_ASUS_WMI))
+		return false;
+
 	ret = asus_wmi_evaluate_method(ASUS_WMI_METHODID_DSTS2,
 				       ASUS_WMI_DEVID_KBD_BACKLIGHT, 0, &value);
 	hid_dbg(hdev, "WMI backlight check: rc %d value %x", ret, value);
-- 
2.18.0

Re: [PATCH] HID: asus: fix build warning wiht CONFIG_ASUS_WMI disabled

[Geert Uytterhoeven]

On Fri, Nov 2, 2018 at 4:16 PM Arnd Bergmann <arnd@arndb.de> 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

Re: [PATCH] HID: asus: fix build warning wiht CONFIG_ASUS_WMI disabled

[Jiri Kosina]

On Fri, 2 Nov 2018, Arnd Bergmann 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>

Applied to for-4.20/upstream-fixes. Thanks,

-- 
Jiri Kosina
SUSE Labs