+/**
+ * _base_build_sg_scmd - main sg creation routine
+ * @ioc: per adapter object
+ * @scmd: scsi command
+ * @smid: system request message index
+ * Context: none.
+ *
+ * The main routine that builds scatter gather table from a given
+ * scsi request sent via the .queuecommand main handler.
+ *
+ * Returns 0 success, anything else error
+ */
+static int
+_base_build_sg_scmd(struct MPT3SAS_ADAPTER *ioc,
+ struct scsi_cmnd *scmd, u16 smid)
+{
+ Mpi2SCSIIORequest_t *mpi_request;
+ dma_addr_t chain_dma;
+ struct scatterlist *sg_scmd;
+ void *sg_local, *chain;
+ u32 chain_offset;
+ u32 chain_length;
+ u32 chain_flags;
+ int sges_left;
+ u32 sges_in_segment;
+ u32 sgl_flags;
+ u32 sgl_flags_last_element;
+ u32 sgl_flags_end_buffer;
+ struct chain_tracker *chain_req;
+
+ mpi_request = mpt3sas_base_get_msg_frame(ioc, smid);
+
+ /* init scatter gather flags */
+ sgl_flags = MPI2_SGE_FLAGS_SIMPLE_ELEMENT;
+ if (scmd->sc_data_direction == DMA_TO_DEVICE)
+ sgl_flags |= MPI2_SGE_FLAGS_HOST_TO_IOC;
+ sgl_flags_last_element = (sgl_flags | MPI2_SGE_FLAGS_LAST_ELEMENT)
+ << MPI2_SGE_FLAGS_SHIFT;
+ sgl_flags_end_buffer = (sgl_flags | MPI2_SGE_FLAGS_LAST_ELEMENT |
+ MPI2_SGE_FLAGS_END_OF_BUFFER | MPI2_SGE_FLAGS_END_OF_LIST)
+ << MPI2_SGE_FLAGS_SHIFT;
+ sgl_flags = sgl_flags << MPI2_SGE_FLAGS_SHIFT;
+
+ sg_scmd = scsi_sglist(scmd);
+ sges_left = scsi_dma_map(scmd);
+ if (sges_left < 0) {
+ sdev_printk(KERN_ERR, scmd->device,
+ "pci_map_sg failed: request for %d bytes!\n",
+ scsi_bufflen(scmd));
+ return -ENOMEM;
+ }
+
+ sg_local = &mpi_request->SGL;
+ sges_in_segment = ioc->max_sges_in_main_message;
+ if (sges_left <= sges_in_segment)
+ goto fill_in_last_segment;
+
+ mpi_request->ChainOffset = (offsetof(Mpi2SCSIIORequest_t, SGL) +
+ (sges_in_segment * ioc->sge_size))/4;
+
+ /* fill in main message segment when there is a chain following */
+ while (sges_in_segment) {
+ if (sges_in_segment == 1)
+ ioc->base_add_sg_single(sg_local,
+ sgl_flags_last_element | sg_dma_len(sg_scmd),
+ sg_dma_address(sg_scmd));
+ else
+ ioc->base_add_sg_single(sg_local, sgl_flags |
+ sg_dma_len(sg_scmd), sg_dma_address(sg_scmd));
+ sg_scmd = sg_next(sg_scmd);
+ sg_local += ioc->sge_size;
+ sges_left--;
+ sges_in_segment--;
+ }
+
+ /* initializing the chain flags and pointers */
+ chain_flags = MPI2_SGE_FLAGS_CHAIN_ELEMENT << MPI2_SGE_FLAGS_SHIFT;
+ chain_req = _base_get_chain_buffer_tracker(ioc, smid);
+ if (!chain_req)
+ return -1;
+ chain = chain_req->chain_buffer;
+ chain_dma = chain_req->chain_buffer_dma;
+ do {
+ sges_in_segment = (sges_left <=
+ ioc->max_sges_in_chain_message) ? sges_left :
+ ioc->max_sges_in_chain_message;
+ chain_offset = (sges_left == sges_in_segment) ?
+ 0 : (sges_in_segment * ioc->sge_size)/4;
+ chain_length = sges_in_segment * ioc->sge_size;
+ if (chain_offset) {
+ chain_offset = chain_offset <<
+ MPI2_SGE_CHAIN_OFFSET_SHIFT;
+ chain_length += ioc->sge_size;
+ }
+ ioc->base_add_sg_single(sg_local, chain_flags | chain_offset |
+ chain_length, chain_dma);
+ sg_local = chain;
+ if (!chain_offset)
+ goto fill_in_last_segment;
+
+ /* fill in chain segments */
+ while (sges_in_segment) {
+ if (sges_in_segment == 1)
+ ioc->base_add_sg_single(sg_local,
+ sgl_flags_last_element |
+ sg_dma_len(sg_scmd),
+ sg_dma_address(sg_scmd));
+ else
+ ioc->base_add_sg_single(sg_local, sgl_flags |
+ sg_dma_len(sg_scmd),
+ sg_dma_address(sg_scmd));
+ sg_scmd = sg_next(sg_scmd);
+ sg_local += ioc->sge_size;
+ sges_left--;
+ sges_in_segment--;
+ }
+
+ chain_req = _base_get_chain_buffer_tracker(ioc, smid);
+ if (!chain_req)
+ return -1;
+ chain = chain_req->chain_buffer;
+ chain_dma = chain_req->chain_buffer_dma;
+ } while (1);
+
+
+ fill_in_last_segment:
+
+ /* fill the last segment */
+ while (sges_left) {
+ if (sges_left == 1)
+ ioc->base_add_sg_single(sg_local, sgl_flags_end_buffer |
+ sg_dma_len(sg_scmd), sg_dma_address(sg_scmd));
+ else
+ ioc->base_add_sg_single(sg_local, sgl_flags |
+ sg_dma_len(sg_scmd), sg_dma_address(sg_scmd));
+ sg_scmd = sg_next(sg_scmd);
+ sg_local += ioc->sge_size;
+ sges_left--;
+ }
+
+ return 0;
+}
+