{"action":"opened","issue":{"url":"https://api.github.com/repos/Xilinx/PYNQ/issues/613","repository_url":"https://api.github.com/repos/Xilinx/PYNQ","labels_url":"https://api.github.com/repos/Xilinx/PYNQ/issues/613/labels{/name}","comments_url":"https://api.github.com/repos/Xilinx/PYNQ/issues/613/comments","events_url":"https://api.github.com/repos/Xilinx/PYNQ/issues/613/events","html_url":"https://github.com/Xilinx/PYNQ/issues/613","id":313161202,"number":613,"title":"PYNQ Linux driver architecture","user":{"login":"zhaozhixu","id":12733773,"avatar_url":"https://avatars3.githubusercontent.com/u/12733773?v=4","gravatar_id":"","url":"https://api.github.com/users/zhaozhixu","html_url":"https://github.com/zhaozhixu","followers_url":"https://api.github.com/users/zhaozhixu/followers","following_url":"https://api.github.com/users/zhaozhixu/following{/other_user}","gists_url":"https://api.github.com/users/zhaozhixu/gists{/gist_id}","starred_url":"https://api.github.com/users/zhaozhixu/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/zhaozhixu/subscriptions","organizations_url":"https://api.github.com/users/zhaozhixu/orgs","repos_url":"https://api.github.com/users/zhaozhixu/repos","events_url":"https://api.github.com/users/zhaozhixu/events{/privacy}","received_events_url":"https://api.github.com/users/zhaozhixu/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":0,"created_at":"2018-04-11T03:29:21Z","updated_at":"2018-04-11T03:29:21Z","closed_at":null,"author_association":"NONE","body":"Hi, I'm new to PYNQ and I'm trying to understand the architecture about PYNQ Linux drivers. But I can't understand why they can bypass Linux kernel and directly operate hardware registers.\r\n\r\nFrom the source code of PYNQ, I find out that the drivers are all built upon some C code that directly calls assembly code to read/write hardware registers, without any interaction with Linux Loadable Kernel Module (LKM) system.\r\n\r\nFor example, the DMA driver is defined in PYNQ/pynq/lib/dma.py, which calls a shared object libdma.so, whose data structures and functions are defined in PYNQ/pynq/lib/_pynq/_apf/axidma_v9_1/xaxidma.h, which in the end includes some assembly code defined in PYNQ/pynq/lib/_pynq/_apf/include/xpseudo_asm_gcc.h. Nothing is mentioned about Linux kernel module.\r\n\r\nHow can that work? I mean it totally bypasses the whole Linux memory management system and so on? Is there any resources about this topic?\r\n\r\nThanks!"}}
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