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Lecture 16 - March 10, 2003
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AGENDA:
0 Admin
1 P5 (V1)
2 Ch 3.4: Overview of I/O in MINIX

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0 - ADMIN
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Startout Q: 

Due today: Nothing

Due Wednesday:
* RI #5: Covers Ch 3.4-7 (pp. 179-222)

Local friendly Dungeon programming contest this
  Saturday (March 15). 1-3:30pm or so. Details TBA,
  but pencil it in on your calendars.

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1 - P5 (V1)
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Virtual Serial Port (VSP?)

Anticipate iterating through this program several
  times.

Server
* Reads data from the serial port
* Writes a raw copy of data to a log file
* Fulfills read requests to 1 client
* Makes available to client all data since server
  started running.
* Stops running when killed
- Don't run as official daemon, just as a regular
  process at present.
* reads "vspserver.conf" to get configuration details
  DEVICE="/dev/DEVICE_NAME"
  SPEED=N



Client
* Opens connection to server
* Reads data and writes to standard output until server
  indicates that no more data is available.
* reads "vspclient.conf" to get configuration details
  HOSTIP=N.N.N.N
  HOSTPORT=N
  LOGFILE="name"

Thoughts?







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2 - CH 3.4: OVERVIEW OF I/O IN MINIX
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What questions do you have?
Did you understand the part about the clock & 
  pending_ticks?

How do you decide what work to do in interrupt
  handler vs. in task?

Discuss how keyboard hardware works, scan codes, etc.
  Esp. keypress & release, special keys.

Compare process-structured system vs. monolithic in
  how system calls are processed. Fig 3-14 p. 182.
* trade-offs. Which way do you vote?

Message fields. fig 3-15 p. 184.
Structure for a block device driver. Fig 3-16 p. 185.
Driver.c - pp. 636-641

User-level I/O software: library routines like
  printf, scanf, interface to read, write, etc.

Deadlock handling: "Deadlock, what deadlock?"
* Primary place deadlocks could occur is with implicit
  shared resources, such a proc tab slots, i-node 
  slots, etc.
* Have taken steps to reduce possibility of deadlock.

/usr/spool/locks
* discuss reliability

COS 421 - Lecture Notes #16		SPRING 2003	
COS421-lect-2003-03-10.doc	Page 2	Printed 10.03.03