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developersguide:overviewofminixdrivers

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developersguide:overviewofminixdrivers [2015/04/24 17:11] (current)
jeanbaptisteboric created
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 +====== Overview of Minix 3 drivers ======
 +
 +Drivers are software components used to manage hardware peripherals. In Minix, drivers are implemented as user-mode processes, and they use the micro-kernel to manage the hardware through it.
 +
 +The drivers source code are located under the minix/​drivers/​ directory in the Minix source tree. The binary executables are located under the /service/ directory.
 +
 +===== Unix device drivers =====
 +
 +Like Unix and Unix-likes operating systems, Minix divides drivers in two categories, character and block devices, and they can be accessed just like regular files on the file system by the user-land through device nodes.
 +
 +Driver types differ essentially in what services and operations they support.
 +
 +==== Block device ====
 +
 +A block device treats data in chunks called blocks, each block being composed of a constant number of bytes. Block devices support the seek operation, which allows access to any block at any moment.
 +
 +Block devices generally represents storage media, such as hard disk and CD drives.
 +
 +==== Character device ====
 +
 +A character device treats data as a stream of bytes. Character devices do not support the seek operation and so do not have to actually represent a storage media or even a real hardware peripheral.
 +
 +Character devices represents everything block devices cannot, from real hardware components (printers, serial ports) to virtual, abstract entities (TTY, random number generators...).
 +
 +===== Drivers implementation =====
 +
 +Minix drivers are processes, but unlike other processes they have permission to access their I/O ports through the micro-kernel.
 +
 +==== Low-level protocols ====
 +
 +Drivers interact closely with three important components and so have specialized low-level protocols for each of the virtual file server, the reincarnation server and the micro-kernel. Like all processes, drivers communicate with message passing, memory grants and system calls so those protocols are defined in those terms.
 +
 +==== High-level abstraction libraries ====
 +
 +Libraries were created to provide driver developers with a higher-level abstraction interface. Besides easing development,​ those libraries shield the drivers from low-level protocols changes to a certain extent.
 +
 +The corresponding driver abstraction libraries are :
 +
 +  * blockdriver : for block-oriented drivers,
 +  * chardriver : for generic character-oriented drivers,
 +  * inputdriver : for drivers communicating with the input server,
 +  * netdriver : for network device drivers.
  
developersguide/overviewofminixdrivers.txt · Last modified: 2015/04/24 17:11 by jeanbaptisteboric