2 messages, 2 authors, 2012-10-25 · open the first message on its own page
From: ratheesh kannoth <hidden>
Date: 2012-10-25 08:58:56
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
From: Alexander Duyck <hidden>
Date: 2012-10-25 16:23:33
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