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Chapter 6: Writing Kernel-level GIO Device Drivers


This chapter provides in-depth information about drivers that interface to the GIO (Graphics Input/Output) bus. It describes the system configuration for GIO device drivers and introduces several GIO-specific functions you must include in your device driver. There are several models for performing DMA operations. Which model you choose for your device driver depends on the capability of the device, which may either require a software implementation or have hardware support for scatter/gather. Memory-mapped, user-level drivers for GIO devices are not supported; all GIO drivers must be kernel-level drivers.

This chapter contains the following sections:


GIO-bus Architecture
Determining GIO Device Addresses
Including GIO Device Drivers in the Kernel
Writing edtinit()
GIO-specific Functions
GIO Interrupt Handler
Programmed I/O (PIO)
DMA Operations
Memory Parity Workarounds
GIO Devices with Hardware-supported Scatter/Gather Capability
DMA on GIO Devices Without Scatter/Gather Capability
Device Driver Example

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