Writing Device Drivers

tran_getcap() Entry Point

The tran_getcap(9E) entry point for a SCSI HBA driver is called by scsi_ifgetcap(9F). The target driver calls scsi_ifgetcap() to determine the current value of one of a set of SCSA-defined capabilities.

The target driver can request the current setting of the capability for a particular target by setting the whom parameter to nonzero. A whom value of zero indicates a request for the current setting of the general capability for the SCSI bus or for adapter hardware.

The tran_getcap() entry point should return -1 for undefined capabilities or the current value of the requested capability.

The HBA driver can use the function scsi_hba_lookup_capstr(9F) to compare the capability string against the canonical set of defined capabilities.


Example 18–10 HBA Driver tran_getcap(9E) Entry Point

static int
isp_scsi_getcap(
    struct scsi_address    *ap,
    char                   *cap,
    int                    whom)
{
    struct isp             *isp;
    int                    rval = 0;
    u_char                 tgt = ap->a_target;
    /*
      * We don't allow getting capabilities for other targets
    */
    if (cap == NULL || whom  == 0) {
        return (-1);
    }
    isp = (struct isp *)ap->a_hba_tran->tran_hba_private;
    ISP_MUTEX_ENTER(isp);

    switch (scsi_hba_lookup_capstr(cap)) {
      case SCSI_CAP_DMA_MAX:
          rval = 1 << 24; /* Limit to 16MB max transfer */
          break;
      case SCSI_CAP_MSG_OUT:
          rval = 1;
          break;
      case SCSI_CAP_DISCONNECT:
          if ((isp->isp_target_scsi_options[tgt] &
            SCSI_OPTIONS_DR) == 0) {
              break;
          } else if (
              (isp->isp_cap[tgt] & ISP_CAP_DISCONNECT) == 0) {
                  break;
          }
          rval = 1;
          break;
      case SCSI_CAP_SYNCHRONOUS:
          if ((isp->isp_target_scsi_options[tgt] &
            SCSI_OPTIONS_SYNC) == 0) {
              break;
          } else if (
              (isp->isp_cap[tgt] & ISP_CAP_SYNC) == 0) {
                  break;
          }
          rval = 1;
          break;
      case SCSI_CAP_WIDE_XFER:
          if ((isp->isp_target_scsi_options[tgt] &
            SCSI_OPTIONS_WIDE) == 0) {
              break;
          } else if (
              (isp->isp_cap[tgt] & ISP_CAP_WIDE) == 0) {
                  break;
          }
          rval = 1;
          break;
      case SCSI_CAP_TAGGED_QING:
          if ((isp->isp_target_scsi_options[tgt] &
            SCSI_OPTIONS_DR) == 0 ||
            (isp->isp_target_scsi_options[tgt] &
            SCSI_OPTIONS_TAG) == 0) {
              break;
          } else if (
              (isp->isp_cap[tgt] & ISP_CAP_TAG) == 0) {
                  break;
          }
          rval = 1;
          break;
      case SCSI_CAP_UNTAGGED_QING:
          rval = 1;
          break;
      case SCSI_CAP_PARITY:
          if (isp->isp_target_scsi_options[tgt] &
            SCSI_OPTIONS_PARITY) {
              rval = 1;
          }
          break;
      case SCSI_CAP_INITIATOR_ID:
          rval = isp->isp_initiator_id;
          break;
      case SCSI_CAP_ARQ:
          if (isp->isp_cap[tgt] & ISP_CAP_AUTOSENSE) {
              rval = 1;
          }
          break;
      case SCSI_CAP_LINKED_CMDS:
          break;
      case SCSI_CAP_RESET_NOTIFICATION:
         rval = 1;
          break;
      case SCSI_CAP_GEOMETRY:
          rval = (64 << 16) | 32;
          break;
      default:
          rval = -1;
          break;
    }
    ISP_MUTEX_EXIT(isp);
    return (rval);
}