ISAbus--Example Three

A DMA engine on an ISA bus in an x86 machine has the following attributes:

• It accesses only the first 16 megabytes of memory.

• It performs transfers to segments up to 32 Kbytes in size.

• It has a 16-bit counter register.

• It can handle byte-aligned transfers.

• It supports 1-, 2- and 4-byte burst sizes.

• It has a minimum effective transfer size of 1 byte.

• It can hold up to 17 scatter-gather transfers.

The resulting attribute structure is:

	static ddi_dma_attr_t attributes = {
 		DMA_ATTR_V0,		/* Version number */
 		0x00000000,			/* low address */
 		0x00FFFFFF,			/* high address */
 		0xFFFF,				/* counter register max */
 		1,						/* byte alignment */
 		0x7,					/* burst sizes */
 		0x1,					/* minimum transfer size */
 		0xFFFFFFFF,			/* max xfer size */
 		0x00007FFF,			/* address register max */
 		17,					/* no scatter-gather */
 		512,					/* device operates on sectors */
 		0,						/* attr flag: set to 0 */
 	};