linux-kernel - [PATCH v2] [media] fix warning on v4l2_subdev

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Message-Id: <20170719192338.2671881-1-arnd@arndb.de>
Date:   Wed, 19 Jul 2017 21:23:27 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Hans Verkuil <hans.verkuil@...co.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] [media] fix warning on v4l2_subdev_call() result interpreted as bool

v4l2_subdev_call is a macro returning whatever the callback return
type is, usually 'int'. With gcc-7 and ccache, this can lead to
many wanings like:

media/platform/pxa_camera.c: In function 'pxa_mbus_build_fmts_xlate':
media/platform/pxa_camera.c:766:27: error: ?: using integer constants in boolean context [-Werror=int-in-bool-context]
  while (!v4l2_subdev_call(subdev, pad, enum_mbus_code, NULL, &code)) {
media/atomisp/pci/atomisp2/atomisp_cmd.c: In function 'atomisp_s_ae_window':
media/atomisp/pci/atomisp2/atomisp_cmd.c:6414:52: error: ?: using integer constants in boolean context [-Werror=int-in-bool-context]
  if (v4l2_subdev_call(isp->inputs[asd->input_curr].camera,

The problem here is that after preprocessing, we the compiler
sees a variation of

	if (a ? 0 : 2)

that it thinks is suspicious.

This replaces the ?: operator with an different expression that
does the same thing in a more easily readable way that cannot
tigger the warning

Link: https://lkml.org/lkml/2017/7/14/156
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
v2: replace large patch touching all the users with a simpler
    change to the macro itself.
---
 include/media/v4l2-subdev.h | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 0f92ebd2d710..e83872078376 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -982,8 +982,16 @@ void v4l2_subdev_init(struct v4l2_subdev *sd,
  * Example: err = v4l2_subdev_call(sd, video, s_std, norm);
  */
 #define v4l2_subdev_call(sd, o, f, args...)				\
-	(!(sd) ? -ENODEV : (((sd)->ops->o && (sd)->ops->o->f) ?	\
-		(sd)->ops->o->f((sd), ##args) : -ENOIOCTLCMD))
+	({								\
+		int __result;						\
+		if (!(sd))						\
+			__result = -ENODEV;				\
+		else if (!((sd)->ops->o && (sd)->ops->o->f))		\
+			__result = -ENOIOCTLCMD;			\
+		else							\
+			__result = (sd)->ops->o->f((sd), ##args);	\
+		__result;						\
+	})
 
 #define v4l2_subdev_has_op(sd, o, f) \
 	((sd)->ops->o && (sd)->ops->o->f)
-- 
2.9.0