SBus Example

A DMA engine on an SBus in a SPARC machine has the following attributes:

• It can access only addresses ranging from 0xFF000000 to 0xFFFFFFFF.

• It has a 32-bit DMA 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 has a 32-bit address register.

• It doesn't have a scatter-gather list.

• The device operates on sectors only (for example a disk).

The resulting attribute structure is:

static ddi_dma_attr_t attributes = {
    DMA_ATTR_V0,      /* Version number */
    0xFF000000,       /* low address */
    0xFFFFFFFF,       /* high address */
    0xFFFFFFFF,       /* counter register max */
    1,                /* byte alignment */
    0x7,              /* burst sizes: 0x1 | 0x2 | 0x4 */
    0x1,              /* minimum transfer size */
    0xFFFFFFFF,       /* max xfer size */
    0xFFFFFFFF,       /* address register max */
    1,                /* no scatter-gather */
    512,              /* device operates on sectors */
    0,                /* attr flag: set to 0 */
};