eisa_dma_buf(D4)

NAME
     eisa_dma_buf - EISA DMA buffer descriptor structure

SYNOPSIS
     #include <sys/types.h>
     #include <sys/eisa.h>

DESCRIPTION
     The EISA DMA buffer descriptor structure is used to specify the data to
     be transferred by a DMA operation.

USAGE
     Each DMA operation is controlled by a DMA command block [see
     eisa_dma_cb(D4)] structure that includes a pointer to linked list of
     eisa_dma_buf structures.

     Each eisa_dma_buf structure provides the physical address and size of a
     data block involved in a DMA transfer.  Scatter/gather operations
     involving multiple data blocks may be implemented by linking together
     multiple eisa_dma_bufs in a singly-linked list.  Each eisa_dma_buf
     includes the virtual address of the next EISA DMA buffer descriptor in
     the list.

     EISA DMA buffer descriptor structures should only be allocated via
     eisa_dma_get_buf(D3X).  Although drivers may access the members listed
     below, they should not make any assumptions about the size of the
     structure or the contents of other fields in the structure.

   Structure Definitions
     The eisa_dma_buf structure contains the following members:

     ushort_t             count;      /* size of block*/
     paddr_t              address;    /* physical address of data block */
     struct eisa_dma_buf  *next_buf;  /* next buffer descriptor */
     ushort_t             count_hi;   /* for big blocks */
     paddr_t              stopval;    /* ring buffer stop */
     The members of the eisa_dma_buf structure are:

     count specifies the low-order 16 bits of the size of the data block in
     bytes.

     address specifies the physical address of the data block.

     next_buf specifies the virtual address of the next eisa_dma_buf in a
     linked list of EISA DMA buffer descriptors.  It should be NULL if the
     buffer descriptor is the last one in the list.  Note that an EISA DMA
     buffer descriptor allocated by eisa_dma_get_buf will be zeroed out
     initially, thus no explicit initialization is required for this field if
     a value of NULL is desired.
     count_hi specifies the high-order 16 bits of the size of the data block
     in bytes.  Since a eisa_dma_buf allocated by eisa_dma_get_buf is
     initially zeroed out, no explicit initialization is required for this
     field if the size of the data block may be specified by a ushort_t.
     stopval specifies the physical address used to terminate an EISA ring
     buffer. This field is used in conjunction with the reqr_ringstopP field
     in the eisa_dma_cb structure.  It should be left as NULL if this EISA
     feature is not used.

REFERENCES
     eisa_dma_cb(D4), eisa_dma_free_buf(D3X), eisa_dma_get_buf(D3X)