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Date: Thu, 25 Oct 2012 09:21:54 -0700 From: Alexander Duyck <alexander.h.duyck@...el.com> To: ratheesh kannoth <ratheesh.ksz@...il.com> CC: e1000-devel@...ts.sourceforge.net, netdev@...r.kernel.org Subject: Re: [E1000-devel] dma_map_page and dma_map_single We use dma_map_single here because we have a virtual pointer and not a page. If you look in the kernel at the file include/asm-generic/dma-mapping-common.h you will see that dma_map_single_attrs which is what ends up being called when we call dma_map_single will convert the pointer to a page and then call map_page. This way we don't have to place the overhead for the code directly in our driver. Thanks, Alex On 10/25/2012 01:58 AM, ratheesh kannoth wrote: > Hi , > > I was looking at tx_map ( igb-3.3.6 ) in igb driver. I could see that > dma_map_single is used for first buffer and dma_map_page is used for > the fragments. > > What is the real difference between these api ? we can replace > dma_map_single with dma_map_page. then why we used dma_map_single > here ?. > > Thanks, > Ratheesh > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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