Reading: I/O Devices . Read OSTEP chapter 36 ( http://pages.cs.wisc.edu/~remzi/O

Question

Reading: I/O Devices. Read OSTEP chapter 36 (http://pages.cs.wisc.edu/~remzi/OSTEP/file-devices.pdf) and answer the following questions:

1. When would you tend to prefer polling to interrupts in interacting with an I/O device? a) when the device supports many commands, b) when the device can perform a command quickly, or c) when the interrupt handler table is very large.

2. (Yes/No) Is it possible for software to interact with an I/O device using both polling and interrupts?

3. (T/F) About ? of the Linux source code is device driver code.

Explanation / Answer

Answers:

1)

c): when the interrupt handler table is very large.

explanation:

Instead of polling the device repeatedly ,the OS can issue a request ,put the calling procees to sleep and context switch to another task. When the device is finally finished with the operation ,it will raise a hardware interrupt ,causing the CPU tojump into the OS at a ISR or interrupt handler.

2) yes

It is possible for sodtware to interact with an I/O device using both polling and interrupts.

3)

False

Reason : Studiesof the linux kernel reveal that over 70% of OS code is found in device drivers.

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