Hello NetBSD gurus!!,
    I have a memory mapped network card. And I am map the memory and then
access the memory using
 bus_space_write_4(sc->pm_memt, sc->pm_sh,..) the pm_memt and pm_sh are
returned by pci_mapreg_map() which I uae for mapping the memory.

    Is every thing done properly? I hope so.

    Now the problem is after some while the whenever I try to read the
registers they all give content as 0xffffffff . May I know the reason? Pls
Help.

Thanking you,
Vikram

/*
 * REFERence drivers if_de.c and tulip.c
 * Attach for autoconfig to find.  Initialise the lists and return...
 */
void my_pci_attach( struct device *parent,
      struct device *self,
      void * const aux)
{
   /* nothing to do for my, this is where resources that
      need to be allocated/initialised before open is called
      can be set up */
 my_softc * const sc = (my_softc *) self;
    struct pci_attach_args * const pa = (struct pci_attach_args *) aux;
    const int unit = sc->pm_dev.dv_unit;
 pci_intr_handle_t ih;// interrupt handler
 const char *intrstr;
// int retval;
// bus_addr_t csrbase;
 struct ifnet *ifp;
 u_int8_t enaddr[ETHER_ADDR_LEN];
 bus_space_tag_t memt;
 bus_space_handle_t memh;
 int memh_valid,s;

 printf("my_:_ Number of mys found = %d\n",unit + 1);

 sc->pm_pc = pa->pa_pc;

 file://Get the device info
 (sc)->pm_pci_busno = parent;
 (sc)->pm_pci_devno = pa->pa_device;

 file://make sure bus mastering is enabled
 pci_conf_write(pa->pa_pc, pa->pa_tag, PCI_COMMAND_STATUS_REG,
    pci_conf_read(pa->pa_pc, pa->pa_tag, PCI_COMMAND_STATUS_REG) |
    PCI_COMMAND_MASTER_ENABLE);

 file://interrupt map
   if (pci_intr_map(sc->pm_pc, pa->pa_intrtag, pa->pa_intrpin,
                                        pa->pa_intrline, &ih))
 {
     printf("%s: couldn't map interrupt\n", "my_:_");
     return;
 }
 sc->pm_intr = my_intr;// link the my intrupt hadler with driver data
 intrstr = pci_intr_string(sc->pm_pc, ih);
 sc->pm_ih = pci_intr_establish(sc->pm_pc, ih, IPL_NET, sc->pm_intr, sc);
 if (sc->pm_ih == NULL)
 {
  printf("%s: couldn't establish interrupt\n", "my_:_");
  if (intrstr != NULL)
   printf(" at %s", intrstr);
  printf("\n");
  return;
 }
 printf("%s: interrupting at %s\n", "my_:_", intrstr);
 sc->pm_sdhook = shutdownhook_establish(my_shutdown, sc);

 // Copying the names.
    bcopy(self->dv_xname, sc->pm_ethercom.ec_if.if_xname, IFNAMSIZ);
    sc->pm_ethercom.ec_if.if_softc = sc;
    sc->pm_pc = pa->pa_pc;

 // Saving the dmatag for the future use
 sc->pm_dmat = pa->pa_dmat;
 sc->cur_tx = sc->cur_rx = 0;
    file://csr_base = 0;// Check if this is needed

  // My card has stored memory mapped address at PCI_CBIO
  // For Memory mapped access
  memh_valid = (pci_mapreg_map(pa, PCI_CBIO,
         PCI_MAPREG_TYPE_MEM |
         PCI_MAPREG_MEM_TYPE_32BIT,
         0, &memt, &memh, NULL, NULL) == 0);
  if (memh_valid)
  {
    sc->pm_memt = memt;
    sc->pm_sh = memh;
  } else
  {
    printf("my_:_ unable to map device registers\n");
    return;
  }

  // Make sure bus mastering is enabled.
  pci_conf_write(pa->pa_pc, pa->pa_tag, PCI_COMMAND_STATUS_REG,
      pci_conf_read(pa->pa_pc, pa->pa_tag,
      PCI_COMMAND_STATUS_REG) |
      PCI_COMMAND_MASTER_ENABLE);


  // Display all the registers
  DisplayReg(sc);

  if( my_busdma_allocmem(sc) )
    goto LoadFail; // BusDma allocation problem!
  printf("my_:_ bus_dmamap ing successful\n");

  if( my_init_ring(sc) )
    goto LoadFail; // Can't init the descriptor memories!
  printf("my_:_ initing the descriptor memories\n");

  // Give driver reset
  my_reset(sc);

  printf("my_:_ Driver Reset ***** Done\n");

// Suppose by this time the media is detected and here I am hardcoding
// that until I write the Link checking code
  sc->my_media = 7; // 100 Mbps



  // Any change after the reset?
//  DisplayReg(sc);

  /* Announce ourselves. */
  printf("%s: %s Ethernet address %s\n", sc->pm_dev.dv_xname,
  "my",
  ether_sprintf(enaddr));


  s = splnet();
  /*
  * Initialize our media structures.  This may probe the MII, if
  * present.
  */
  // (*sc->pm_mediasw->tmsw_init)(sc);

  // For attaching to if_config etc
  ifp = &sc->pm_ethercom.ec_if;

  strcpy(ifp->if_xname, sc->pm_dev.dv_xname);
  ifp->if_softc = sc;
  ifp->if_flags = IFF_BROADCAST|IFF_SIMPLEX|IFF_NOTRAILERS|IFF_MULTICAST;
  ifp->if_ioctl = my_ifioctl;
  ifp->if_start = my_ifstart;
  ifp->if_watchdog = my_ifwatchdog;
  ifp->if_timer = 1;
  /*
   * the ifp is initialised
   */
     ifp->if_output = ether_output;

#if defined(IFM_ETHER)
  ifmedia_init(&sc->my_ifmedia,0,my_ifmedia_change,my_ifmedia_status);
  my_ifmedia_add(sc);
#endif
  /*
  * Attach the interface.
  */
  if_attach(ifp);
  ether_ifattach(ifp, enaddr);
#if NBPFILTER > 0
  bpfattach(&sc->pm_ethercom.ec_if.if_bpf, ifp, DLT_EN10MB,sizeof(struct
ether_header));
#endif

#if defined(__NetBSD__) && NRND > 0
  // For kernel entropy collection
  rnd_attach_source(&sc->my_rndsource, sc->pm_dev.dv_xname,RND_TYPE_NET, 0);
#endif

  splx(s);



  /*
  * Driver loaded Successfully
  */
  printf("my_:_ Driver loading successful\n");
  return;

LoadFail:
  printf("my_:_ Loading my failed.");
  return;
}