Specifications

This is the Title of the Book, eMatter Edition

Quick Reference

463

int request_dma(unsigned int channel, const char *name);

void free_dma(unsigned int channel);

Access the DMA registry. Registration must be performed before using ISA DMA

channels.

unsigned long claim_dma_lock( );

void release_dma_lock(unsigned long flags);

Acquire and release the DMA spinlock, which must be held prior to calling the

other ISA DMA functions described later in this list. They also disable and reen-

able interrupts on the local processor.

void set_dma_mode(unsigned int channel, char mode);

void set_dma_addr(unsigned int channel, unsigned int addr);

void set_dma_count(unsigned int channel, unsigned int count);

Program DMA information in the DMA controller. addr is a bus address.

void disable_dma(unsigned int channel);

void enable_dma(unsigned int channel);

A DMA channel must be disabled during configuration. These functions change

the status of the DMA channel.

int get_dma_residue(unsigned int channel);

If the driver needs to know how a DMA transfer is proceeding, it can call this

function, which returns the number of data transfers that are yet to be com-

pleted. After successful completion of DMA, the function returns

0; the value is

unpredictable while data is being transferred.

void clear_dma_ff(unsigned int channel)

The DMA flip-flop is used by the controller to transfer 16-bit values by means of

two 8-bit operations. It must be cleared before sending any data to the controller.

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