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48 lines
1.4 KiB
Markdown
48 lines
1.4 KiB
Markdown
---
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title: "16-device-drivers"
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aliases:
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tags:
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- lecture
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- cosc204
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---
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# Device controller and driver
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driver Defn: a special kernel module that contrls the operations of a device with the device specific information
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controller Defn: a hardware unit on a device that can know and control a devices status or behaviour, which communicates with the CPU via a driver
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# Types of IO devices
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- character stream vs block
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- swqeuential vs random access
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- synchronous vs async
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- sharable or dedicated
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OS provides a consistent interface for them in the `/dev` folder (unix systems). e.g., ramdisk device is name `/dev/memdrv`. each device has a file under `/dev` that can be handled with file operations read()/write()
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## block devices
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commands (sent from device driver to device controller)
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- read block
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- write block
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- seek block (for random access block devices)
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the sequence of read/write requests can (should) be optimized
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## character devices
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- commands
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- get char
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- put char
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also support buffering (accepting keyboard input line by line) and editing of buffers (e.g., spcial treatement of backspace character)
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# IO models
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IO system calls use different IO models
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- blocking - when a proccess needs IO input it waits to recieve it before c
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- non blocking
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- async
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# IO scheduling and buffering
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# UI for IO devices
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