From mboxrd@z Thu Jan 1 00:00:00 1970 From: phind.uet@gmail.com (phind.uet at gmail.com) Date: Fri, 31 Aug 2018 08:53:29 +0800 Subject: Question about DMA mapping. Message-ID: <498566ed-6ac7-a31c-e540-9974a0796ed2@gmail.com> To: kernelnewbies@lists.kernelnewbies.org List-Id: kernelnewbies.lists.kernelnewbies.org Hi everyone, Thank for your time, I'm new to linux kernel. I am reading LDD3 chapter 15, Dirrect Memory Access section. I see that when I call function /dma_map_single/ and /dma_unmap_single/, I need to pass a direction as a parameter. I wonder what is purpose of it? Does It relate to something like permission? Can I call /dma_map_single /with DMA_BIDIRECTIONAL and then call /dma_unmap_single /with DMA_TO_DEVICE? Will it cause any problem? Thank you very much. -------------- next part -------------- An HTML attachment was scrubbed... URL: