Overview

This chapter discusses the management and operation of Input/Output (I/O) systems in operating systems. It covers the role of device drivers, data movement, polling, interrupts, Direct Memory Access (DMA), kernel I/O subsystems, and their components.

I/O Structure in Computer Systems

Key Points:

• Managing I/O devices is a critical component of operating system design.
• Operating systems use device drivers to manage and interact with various I/O devices.
  • Device drivers are modular components that handle a device or a similar category of devices.

Device Communication:

• Data transfer between devices and the computer occurs through device controllers.
• For each device controller, there is a corresponding device driver within the operating system.

Communication Between Host and Devices

Polling and Interrupts:

• The host and device controller communicate to process I/O requests.
• Polling:
  • The host actively checks the device's readiness for data transfer.
  • Efficient for fast devices.
  • Inefficient if the device is rarely ready, as the host spends time checking unnecessarily.
• Interrupts:
  • Used when polling is inefficient.
  • The device interrupts the host when it is ready, eliminating unnecessary checks.

Direct Memory Access (DMA)

Definition:

• DMA is a special-purpose processor used for transferring large quantities of data (e.g., between disk controllers and memory) without continuous CPU involvement.