netdev - Re: [PATCH net] gianfar: Fix dma check map error when DMA_API

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Message-ID: <20141211020646.GB18701@pek-khao-d1.corp.ad.wrs.com>
Date:	Thu, 11 Dec 2014 10:06:46 +0800
From:	Kevin Hao <haokexin@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	claudiu.manoil@...escale.com, netdev@...r.kernel.org
Subject: Re: [PATCH net] gianfar: Fix dma check map error when DMA_API_DEBUG
 is enabled

On Wed, Dec 10, 2014 at 01:13:47PM -0500, David Miller wrote:
> From: Claudiu Manoil <claudiu.manoil@...escale.com>
> Date: Tue, 9 Dec 2014 16:24:35 +0200
> 
> > From: Kevin Hao <haokexin@...il.com>
> > 
> > We need to use dma_mapping_error() to check the dma address returned
> > by dma_map_single/page(). Otherwise we would get warning like this:
>  ...
> > For TX, we need to unmap the pages which has already been mapped and
> > free the skb before return. For RX, just let the rxbdp as unempty.
> > We can retry to initialize it to empty in next round.
> > 
> > Signed-off-by: Kevin Hao <haokexin@...il.com>
> > Signed-off-by: Claudiu Manoil <claudiu.manoil@...escale.com>
> 
> The RX behavior needs to be adjusted.
> 
> You should never leave holes in the RX ring, ever.
> 
> Instead, try allocating the new RX skb first, and only if
> you are successful should you pass up the original SKB.  If
> it fails, then reuse the original SKB in the RX ring.

OK, will do.

Thanks,
Kevin

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