linux-kernel - Re: [PATCH 1/1] videobuf: Initialize lists in videobuf

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Date:	Wed, 17 Nov 2010 13:37:33 +0100
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Hans Verkuil <hverkuil@...all.nl>
Cc:	Andrew Chew <AChew@...dia.com>,
	"'Figo.zhang'" <zhangtianfei@...dcoretech.com>,
	"pawel@...iak.com" <pawel@...iak.com>,
	"linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] videobuf: Initialize lists in videobuf_buffer.

Hi Hans,

On Wednesday 17 November 2010 08:11:06 Hans Verkuil wrote:
> On Wednesday, November 17, 2010 02:38:09 Andrew Chew wrote:
> > > > diff --git a/drivers/media/video/videobuf-dma-contig.c
> > > 
> > > b/drivers/media/video/videobuf-dma-contig.c
> > > 
> > > > index c969111..f7e0f86 100644
> > > > --- a/drivers/media/video/videobuf-dma-contig.c
> > > > +++ b/drivers/media/video/videobuf-dma-contig.c
> > > > @@ -193,6 +193,8 @@ static struct videobuf_buffer
> > > 
> > > *__videobuf_alloc_vb(size_t size)
> > > 
> > > >   	if (vb) {
> > > >   	
> > > >   		mem = vb->priv = ((char *)vb) + size;
> > > >   		mem->magic = MAGIC_DC_MEM;
> > > > 
> > > > +		INIT_LIST_HEAD(&vb->stream);
> > > > +		INIT_LIST_HEAD(&vb->queue);
> > > 
> > > i think it no need to be init, it just a list-entry.
> > 
> > Okay, if that's really the case, then sh_mobile_ceu_camera.c,
> > pxa_camera.c, mx1_camera.c, mx2_camera.c, and omap1_camera.c needs to be
> > fixed to remove that WARN_ON(!list_empty(&vb->queue)); in their
> > videobuf_prepare() methods, because those WARN_ON's are assuming that
> > vb->queue is properly initialized as a list head.
> > 
> > Which will it be?
> 
> These list entries need to be inited. It is bad form to have uninitialized
> list entries. It is not as if this is a big deal to initialize them
> properly.

I disagree with that. List heads must be initialized, but there's no point in 
initializing list entries.

-- 
Regards,

Laurent Pinchart
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