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DMA (Direct Memory Access) driver
[Device Drivers]

Functions
void	dma_xfer (unsigned channel, addr_t physaddr, size_t length, bool read)
	Set up a DMA transfer between a device and memory. Parameters: channel  The 8-bit channel number (0..3). physaddr  The physical address of the buffer. length  The size of the buffer. read  If it is TRUE the transfer will be from memory to device, otherwise will be from device to memory.
Variables
dma_channel_t	dmainfo []
	Definition of DMA channels.

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Detailed Description

The DMA (Direct Memory Access) low level driver (based on i386-architecture).

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Function Documentation

void dma_xfer (  unsigned    channel, addr_t    physaddr, size_t    length, bool    read )

Set up a DMA transfer between a device and memory. Parameters: channel  The 8-bit channel number (0..3). physaddr  The physical address of the buffer. length  The size of the buffer. read  If it is TRUE the transfer will be from memory to device, otherwise will be from device to memory. Definition at line 47 of file dma.c. { int page, offset; if (channel > 3) return; // calculate dma page and offset // page = physaddr >> 16; offset = physaddr & 0xFFFF; length -= 1; // with dma, if you want k bytes, you ask for k-1 // disable(); // set the mask bit for the channel // outportb(0x0A, channel | 0x04); // clear flipflop // outportb(0x0C, 0x00); // set DMA mode (write+single+r/w) // outportb(0x0B, (read ? 0x48 : 0x44) + channel); // set DMA page // outportb(dmainfo[channel].page, page); // set DMA offset // outportb(dmainfo[channel].offset, offset & 0xFF); // low byte // outportb(dmainfo[channel].offset, offset >> 8); // high byte // // set DMA length // outportb(dmainfo[channel].length, length & 0xFF); // low byte // outportb(dmainfo[channel].length, length >> 8); // high byte // // clear DMA mask bit // outportb(0x0A, channel); enable(); }

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Variable Documentation

dma_channel_t dmainfo[] [static]

Initial value: { { 0x87, 0x00, 0x01 }, { 0x83, 0x02, 0x03 }, { 0x81, 0x04, 0x05 }, { 0x82, 0x06, 0x07 } } Definition of DMA channels. Definition at line 32 of file dma.c.

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