Writing Device Drivers

Per-Command Structure

An HBA driver usually needs to define a structure to maintain state for each command submitted by a target driver. The layout of this per-command structure is entirely up to the device driver writer. The layout needs to reflect the capabilities and features of the hardware and the software algorithms that are used in the driver.

The following structure is an example of a per-command structure. The remaining code fragments of this chapter use this structure to illustrate the HBA interfaces.

struct isp_cmd {
     struct isp_request     cmd_isp_request;
     struct isp_response    cmd_isp_response;
     struct scsi_pkt        *cmd_pkt;
     struct isp_cmd         *cmd_forw;
     uint32_t               cmd_dmacount;
     ddi_dma_handle_t       cmd_dmahandle;
     uint_t                 cmd_cookie;
     uint_t                 cmd_ncookies;
     uint_t                 cmd_cookiecnt;
     uint_t                 cmd_nwin;
     uint_t                 cmd_curwin;
     off_t                  cmd_dma_offset;
     uint_t                 cmd_dma_len;
     ddi_dma_cookie_t       cmd_dmacookies[ISP_NDATASEGS];
     u_int                  cmd_flags;
     u_short                cmd_slot;
     u_int                  cmd_cdblen;
     u_int                  cmd_scblen;