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

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Date:   Tue, 15 Jun 2021 10:55:26 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Hans Verkuil <hverkuil@...all.nl>, sakari.ailus@...ux.intel.com,
        laurent.pinchart@...asonboard.com, dan.carpenter@...cle.com,
        mchehab@...nel.org
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        alsa-devel@...a-project.org, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] media: Fix Media Controller API config checks

On 6/15/21 7:36 AM, Hans Verkuil wrote:
> Hi Shuah,
> 
> On 11/06/2021 03:58, Shuah Khan wrote:
>> 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.
> 
> If I test this patch, then I get:
> 
> drivers/media/mc/mc-dev-allocator.c:97:22: error: redefinition of 'media_device_usb_allocate'
>     97 | struct media_device *media_device_usb_allocate(struct usb_device *udev,
>        |                      ^~~~~~~~~~~~~~~~~~~~~~~~~
> In file included from drivers/media/mc/mc-dev-allocator.c:24:
> include/media/media-dev-allocator.h:55:36: note: previous definition of 'media_device_usb_allocate' was here
>     55 | static inline struct media_device *media_device_usb_allocate(
>        |                                    ^~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/media/mc/mc-dev-allocator.c:119:6: error: redefinition of 'media_device_delete'
>    119 | void media_device_delete(struct media_device *mdev, const char *module_name,
>        |      ^~~~~~~~~~~~~~~~~~~
> In file included from drivers/media/mc/mc-dev-allocator.c:24:
> include/media/media-dev-allocator.h:59:20: note: previous definition of 'media_device_delete' was here
>     59 | static inline void media_device_delete(
>        |                    ^~~~~~~~~~~~~~~~~~~
> 
> The .config has:
> 
> # CONFIG_USB_SUPPORT is not set
> CONFIG_MEDIA_CONTROLLER=y
> 

Hans,

Can you share your full config with me?

thanks,
-- Shuah