linux-kernel - Re: [PATCH v2 1/5] dmaengine: add ep93xx DMA support

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Message-ID: <20111116064822.GA2703@mwesterb-mobl.ger.corp.intel.com>
Date:	Wed, 16 Nov 2011 08:48:22 +0200
From:	Mika Westerberg <mika.westerberg@....fi>
To:	H Hartley Sweeten <hartleys@...ionengravers.com>
Cc:	Rafal Prylowski <prylowski@...asoft.pl>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"rmallon@...il.com" <rmallon@...il.com>,
	"vinod.koul@...el.com" <vinod.koul@...el.com>,
	"broonie@...nsource.wolfsonmicro.com" 
	<broonie@...nsource.wolfsonmicro.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
	"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
	"lrg@...com" <lrg@...com>
Subject: Re: [PATCH v2 1/5] dmaengine: add ep93xx DMA support

On Tue, Nov 15, 2011 at 11:59:50AM -0600, H Hartley Sweeten wrote:
> >
> > Index: linux-2.6/drivers/dma/ep93xx_dma.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/dma/ep93xx_dma.c
> > +++ linux-2.6/drivers/dma/ep93xx_dma.c
> > @@ -246,6 +246,7 @@ static void ep93xx_dma_set_active(struct
> >  static struct ep93xx_dma_desc *
> >  ep93xx_dma_get_active(struct ep93xx_dma_chan *edmac)
> >  {
> > +	BUG_ON(list_empty(&edmac->active));
> 
> BUG_ON is evil...
> 
> I'm not sure this is the right way to handle this.
> 
> If your doing dma the list should never be empty.  If it is I think it should
> have been caught way before this.  Mika, do you have any comments?

I agree - the list should never be empty when this is called. The actual bug
is somewhere else.
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