Implementation Method 2 of ISA bus DMA in Linux

In the Linux operating system, implementation method 2 of ISA bus DMA-Linux Enterprise Application-Linux server application information. The following is a detailed description. 3 Linux 8237 DMAC for read/write operations

Because the registers of DMAC are configured in the I/O port space, reading and writing 8237 DMAC is platform-related. For x86 platforms, Linux implements read and write operations on two 8237 DMAC instances in the include/asm-i386/Dma. h header file.

Macro definition of port address and register value 3.1

In Linux, the macro MAX_DMA_CHANNELS is used to indicate the number of current DMA channels of the system, as shown below:

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