Hello

I have a query regarding bus_dma functions on i386 NetBSD 1.4.

We have 3 PCI Video Capture Cards and 3Mb memory is allocated
using bus_dmamem_alloc. A typical RAW image is 400kb and we transfer
25 images/s per card. That's 10Mb per card per second.

Just before we capture an image we set the first 4 bytes
to a magic number and check those bytes when an interrupt
is generated after a capture. If they are the same, we assume
that the capture failed (may happen after a few minutes).
I don't know whether the data is cached somewhere.

(I know that I am transferring a ridiculous amount of data on the PCI bus)

I tried "bus_dmamap_sync" but isn't that a "nop" on i386?
Also what is the need for creating a dmamap anyway?
Are the results I obtain to be expected or is there something I could do?

----------------------------------------------------------------------
static void
fg_attach_pci(parent, self, aux)
     struct device  *parent, *self;
     void *aux;
{
  struct fg_softc        *sc         = (void *) self;
  struct pci_attach_args *pap        = aux;
  bus_space_tag_t        memt;
  bus_space_handle_t     memh;
  bus_size_t             memsize;
  bus_dma_segment_t      segs;
  int rsegs;
  caddr_t kva;
 ...

 pci_mapreg_map(pap, 0x10, PCI_MAPREG_TYPE_MEM, 0,&memt, &memh, NULL,
&memsize);
 bus_dmamem_alloc(pap->pa_dmat, TOTAL_DMA, 0,
0,&segs,1,&rsegs,BUS_DMA_NOWAIT);
 bus_dmamem_map(pap->pa_dmat,&segs,rsegs,TOTAL_DMA,&kva,BUS_DMA_NOWAIT);
 ...
 sc->VideoPhysMem = segs.ds_addr;
 sc->VideoMapMem  = kva;
 ...
}

then just before capture:
...
*(int*)(sc->VideoMapMem) = 0xfacecafe;
...

and the card transfers the image into sc->VideoPhysMem

then interrupt handler (after capture):

int
fg_intr(arg)
     void *arg;
{...
  if ( *(int*)(sc->VideoMapMem) == 0xfacecafe)
  {
    RawFail = 1;
  }
 ...
}

-----------------------------------------------------------

Please help.

Thanks in advance
Riaz Randeree