Chapter 11: Implementing Direct Memory Access (DMA) Support

Direct Memory Access (DMA) is a feature of computer systems that allows devices to access the main system memory without CPU intervention, allowing the CPU to focus on other tasks. Examples of its usage include network traffic acceleration, audio data, or video frame grabbing, and its use is not limited to a particular domain. The peripheral responsible for managing the DMA transactions is the DMA controller, which is present in the majority of modern processors and microcontrollers.

The feature works in the following manner: When the driver needs to transfer a block of data, the driver sets up the DMA controller with the source address, the destination address, and the total number of bytes to copy. The DMA controller then transfers the data from the source to the destination automatically, without stealing CPU cycles. When the number of bytes remaining reaches zero, the block transfer ends, and the driver is notified...