Device Register Structure

DMA-capable devices require more registers than were used in the previous examples.

The following fields are used in the device register structure to support DMA-capable device with no scatter-gather support:

uint32_t      dma_addr;      /* starting address for DMA */
uint32_t      dma_size;      /* amount of data to transfer */

The following fields are used in the device register structure to support DMA-capable devices with scatter-gather support:

struct sglentry {
    uint32_t    dma_addr;
    uint32_t    dma_size;
} sglist[SGLLEN];

caddr_t       iopb_addr;     /* When written, informs the device of the next */
                             /* command's parameter block address. */
                             /* When read after an interrupt, contains */
                             /* the address of the completed command. */