netdev - Re: [net-next PATCH V2 1/3] mm: add dma_addr

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Message-ID: <20190212191917.2ef91a88@carbon>
Date:   Tue, 12 Feb 2019 19:19:17 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     netdev@...r.kernel.org, linux-mm@...ck.org,
        Toke Høiland-Jørgensen 
        <toke@...e.dk>, Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        willy@...radead.org, Saeed Mahameed <saeedm@...lanox.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        mgorman@...hsingularity.net,
        "David S. Miller" <davem@...emloft.net>,
        Tariq Toukan <tariqt@...lanox.com>, brouer@...hat.com
Subject: Re: [net-next PATCH V2 1/3] mm: add dma_addr_t to struct page

On Tue, 12 Feb 2019 10:05:39 -0800
Florian Fainelli <f.fainelli@...il.com> wrote:

> On 2/12/19 6:49 AM, Jesper Dangaard Brouer wrote:
> > The page_pool API is using page->private to store DMA addresses.
> > As pointed out by David Miller we can't use that on 32-bit architectures
> > with 64-bit DMA
> > 
> > This patch adds a new dma_addr_t struct to allow storing DMA addresses
> > 
> > Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
> > Signed-off-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> > Acked-by: Andrew Morton <akpm@...ux-foundation.org>
> > ---
> >  include/linux/mm_types.h |    7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> > index 2c471a2c43fa..581737bd0878 100644
> > --- a/include/linux/mm_types.h
> > +++ b/include/linux/mm_types.h
> > @@ -95,6 +95,13 @@ struct page {
> >  			 */
> >  			unsigned long private;
> >  		};
> > +		struct {	/* page_pool used by netstack */
> > +			/**
> > +			 * @dma_addr: page_pool requires a 64-bit value even on
> > +			 * 32-bit architectures.
> > +			 */  
> 
> Nit: might require? dma_addr_t, as you mention in the commit may have a
> different size based on CONFIG_ARCH_DMA_ADDR_T_64BIT.

So you want me to change the comment to be:

/**
 * @dma_addr: might require a 64-bit value even on
 * 32-bit architectures.
 */

Correctly understood?
-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer