linux-kernel - [PATCH] media: Fix Media Controller API config checks

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Date:   Thu, 10 Jun 2021 19:58:49 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     sakari.ailus@...ux.intel.com, laurent.pinchart@...asonboard.com,
        dan.carpenter@...cle.com, mchehab@...nel.org
Cc:     Shuah Khan <skhan@...uxfoundation.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        alsa-devel@...a-project.org
Subject: [PATCH] media: Fix Media Controller API config checks

Smatch static checker warns that "mdev" can be null:

sound/usb/media.c:287 snd_media_device_create()
    warn: 'mdev' can also be NULL

If CONFIG_MEDIA_CONTROLLER is disabled, this file should not be included
in the build.

The below conditions in the sound/usb/Makefile are in place to ensure that
media.c isn't included in the build.

sound/usb/Makefile:
snd-usb-audio-$(CONFIG_SND_USB_AUDIO_USE_MEDIA_CONTROLLER) += media.o

select SND_USB_AUDIO_USE_MEDIA_CONTROLLER if MEDIA_CONTROLLER &&
       (MEDIA_SUPPORT=y || MEDIA_SUPPORT=SND_USB_AUDIO)

The following config check in include/media/media-dev-allocator.h is
in place to enable the API only when CONFIG_MEDIA_CONTROLLER and
CONFIG_USB are enabled.

 #if defined(CONFIG_MEDIA_CONTROLLER) && defined(CONFIG_USB)

This check doesn't work as intended when CONFIG_USB=m. When CONFIG_USB=m,
CONFIG_USB_MODULE is defined and CONFIG_USB is not. The above config check
doesn't catch that CONFIG_USB is defined as a module and disables the API.
This results in sound/usb enabling Media Controller specific ALSA driver
code, while Media disables the Media Controller API.

Fix the problem requires two changes:

1. Change the check to use IS_ENABLED to detect when CONFIG_USB is enabled
   as a module or static. Since CONFIG_MEDIA_CONTROLLER is a bool, leave
   the check unchanged to be consistent with drivers/media/Makefile.

2. Change the drivers/media/mc/Makefile to include mc-dev-allocator.o
   in mc-objs when CONFIG_USB is y or m.

Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Link: https://lore.kernel.org/alsa-devel/YLeAvT+R22FQ%2FEyw@mwanda/
Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
---
 drivers/media/mc/Makefile           | 2 +-
 include/media/media-dev-allocator.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/media/mc/Makefile b/drivers/media/mc/Makefile
index 119037f0e686..140f0a78540e 100644
--- a/drivers/media/mc/Makefile
+++ b/drivers/media/mc/Makefile
@@ -3,7 +3,7 @@
 mc-objs	:= mc-device.o mc-devnode.o mc-entity.o \
 	   mc-request.o

-ifeq ($(CONFIG_USB),y)
+ifeq ($(CONFIG_USB),$(filter $(CONFIG_USB),y m))
 	mc-objs += mc-dev-allocator.o
 endif

diff --git a/include/media/media-dev-allocator.h b/include/media/media-dev-allocator.h
index b35ea6062596..2ab54d426c64 100644
--- a/include/media/media-dev-allocator.h
+++ b/include/media/media-dev-allocator.h
@@ -19,7 +19,7 @@

 struct usb_device;

-#if defined(CONFIG_MEDIA_CONTROLLER) && defined(CONFIG_USB)
+#if defined(CONFIG_MEDIA_CONTROLLER) && IS_ENABLED(CONFIG_USB)
 /**
  * media_device_usb_allocate() - Allocate and return struct &media device
  *
-- 
2.30.2