linux-kernel - Re: [PATCH] media: cx18: Don't check for address of video

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Date:   Fri, 21 Sep 2018 13:31:37 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     awalls@...metrocast.net,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] media: cx18: Don't check for address of video_dev

On Fri, Sep 21, 2018 at 1:03 PM Nathan Chancellor
<natechancellor@...il.com> wrote:
>
> Clang warns that the address of a pointer will always evaluated as true
> in a boolean context.
>
> drivers/media/pci/cx18/cx18-driver.c:1255:23: warning: address of
> 'cx->streams[i].video_dev' will always evaluate to 'true'
> [-Wpointer-bool-conversion]
>                 if (&cx->streams[i].video_dev)
>                 ~~   ~~~~~~~~~~~~~~~^~~~~~~~~
> 1 warning generated.
>
> Presumably, the contents of video_dev should have been checked, not the
> address. This check has been present since 2009, introduced by commit
> 21a278b85d3c ("V4L/DVB (11619): cx18: Simplify the work handler for
> outgoing mailbox commands")
>
> Reported-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---
>
> Alternatively, this if statement could just be removed since it has
> evaluated to true since 2009 and I assume some issue with this would
> have been discovered by now.
>
>  drivers/media/pci/cx18/cx18-driver.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/media/pci/cx18/cx18-driver.c b/drivers/media/pci/cx18/cx18-driver.c
> index 56763c4ea1a7..753a37c7100a 100644
> --- a/drivers/media/pci/cx18/cx18-driver.c
> +++ b/drivers/media/pci/cx18/cx18-driver.c
> @@ -1252,7 +1252,7 @@ static void cx18_cancel_out_work_orders(struct cx18 *cx)
>  {
>         int i;
>         for (i = 0; i < CX18_MAX_STREAMS; i++)
> -               if (&cx->streams[i].video_dev)
> +               if (cx->streams[i].video_dev)

cx->streams[i].video_dev has the type `struct video_device video_dev`.
So wouldn't this change always be true as well, since the struct is
embedded?

>                         cancel_work_sync(&cx->streams[i].out_work_order);
>  }
>
> --
> 2.19.0
>


-- 
Thanks,
~Nick Desaulniers