For a previously allocated packet with data remaining to be transferred, the tran_init_pkt(9E) entry point must reallocate DMA resources when the following conditions apply:
Partial DMA resources have already been allocated.
A non-zero pkt_resid was returned in the previous call to tran_init_pkt(9E).
bp is not null.
bp->b_bcount is not zero.
When reallocating DMA resources to the next portion of the transfer, tran_init_pkt(9E) must return the amount of DMA resources not allocated for this transfer in the field pkt_resid.
If an error occurs while attempting to move DMA resources, tran_init_pkt(9E) must not free the scsi_pkt(9S). The target driver in this case is responsible for freeing the packet.
If the callback parameter is NULL_FUNC, the tran_init_pkt(9E) entry point must not sleep or call any function that might sleep. If the callback parameter is SLEEP_FUNC and resources are not immediately available, the tran_init_pkt(9E) entry point should sleep. Unless the request is impossible to satisfy, tran_init_pkt() should sleep until resources become available.
static int isp_i_dma_move( struct isp *isp, struct scsi_pkt *pkt, struct buf *bp) { struct isp_cmd *sp = (struct isp_cmd *)pkt->pkt_ha_private; int i; ASSERT(sp->cmd_flags & CFLAG_COMPLETED); sp->cmd_flags &= ~CFLAG_COMPLETED; /* * If there are no more cookies remaining in this window, * must move to the next window first. */ if (sp->cmd_cookie == sp->cmd_ncookies) { /* * For small pkts, leave things where they are */ if (sp->cmd_curwin == sp->cmd_nwin && sp->cmd_nwin == 1) return (1); /* * At last window, cannot move */ if (++sp->cmd_curwin >= sp->cmd_nwin) return (0); if (ddi_dma_getwin(sp->cmd_dmahandle, sp->cmd_curwin, &sp->cmd_dma_offset, &sp->cmd_dma_len, &sp->cmd_dmacookies[0], &sp->cmd_ncookies) == DDI_FAILURE) return (0); sp->cmd_cookie = 0; } else { /* * Still more cookies in this window - get the next one */ ddi_dma_nextcookie(sp->cmd_dmahandle, &sp->cmd_dmacookies[0]); } /* * Get remaining cookies in this window, up to our maximum */ i = 0; for (;;) { sp->cmd_dmacount += sp->cmd_dmacookies[i++].dmac_size; sp->cmd_cookie++; if (i == ISP_NDATASEGS || sp->cmd_cookie == sp->cmd_ncookies) break; ddi_dma_nextcookie(sp->cmd_dmahandle, &sp->cmd_dmacookies[i]); } sp->cmd_cookiecnt = i; pkt->pkt_resid = bp->b_bcount - sp->cmd_dmacount; return (1); }