Subject: Re: [PATCH] fix compiler warning in drivers/media/video/video-buf.c
From: Mauro Carvalho Chehab <mchehab@infradead.org>
To: Andrew Morton <akpm@osdl.org>
Cc: Martin Bligh <mbligh@google.com>, Sujoy Gupta <sujoy@google.com>,
       LKML <linux-kernel@vger.kernel.org>, video4linux-list@redhat.com
In-Reply-To: <20060928105108.88b37304.akpm@osdl.org>
References: <451C070E.8080800@google.com>
	 <20060928105108.88b37304.akpm@osdl.org>
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Date: Fri, 29 Sep 2006 16:54:07 -0300
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Em Qui, 2006-09-28 ?s 10:51 -0700, Andrew Morton escreveu:
> On Thu, 28 Sep 2006 10:31:58 -0700
> Martin Bligh <mbligh@google.com> wrote:

> That being said, this driver is wrong to be storing dma addresses in a
> void*.  And indeed there is a FIXME regarding this at
> include/linux/videodev2.h:476, so I guess hiding this warning won't obscure
> any fault which wasn't already known about..

Yes. The original structure is:

struct v4l2_framebuffer
{
        __u32                   capability;
        __u32                   flags;
        void*                   base;
        struct v4l2_pix_format  fmt;
};

Since this is used at ioctl definition, changing this would break
userspace apps. We might replace this to something like:

struct v4l2_framebuffer
{
        __u32                   capability;
        __u32                   flags;
	union {
	        void*		base_ptr; /*FOO definition to avoid breaking userpace apps */
		dma_addr_t	base;
	}
        struct v4l2_pix_format  fmt;
};

This way, base will have the expected type, and it won't break any
userspace app if sizeof(void *)<=sizeof(base). I think this is true for
all architectures (anyway, if it isn't, v4l is broken anyway).

What do you think?

Cheers, 
Mauro.

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