Re: [UPDATE] 2.4.10-pre2 PCI64, API changes README

[Gerd Knorr <kraxel@bytesex.org>]

Alan Cox wrote:
> > If mmap()'ing the frame buffer and passing this into read() is how
> > this will be done, it simply won't work.  That's the point I'm trying
> > to make.
>  
>  That isnt done anyway - the card executes a risc instruction set for the
>  DMA engine specifying which to skip and draw. So you feed it a base
>  physical address for the fb via ioctl (yes this needs to be a pci device
>  bar and offset I suspect) and then tell it about the fb layout and the like

current bttv tries to find a PCI device for the given physical address by
walking all PCI devices, then check whenever the address falls into one of the
dev->resource memory ranges.  Works fine on i386, but I'm not sure whenever
this works on other platforms, where phys == bus isn't true.

Right now it only sanity-checks the given physical address this way (see
below), but of course I could also pass the found pci_dev to some pci->pci
API.

What addresses are in dev->resource?  Physical?  Bus address?  Are they
unique?

  Gerd

---------------------------- cut here -------------------------
static int
find_videomem(unsigned long from, unsigned long to)
{
        struct pci_dev *dev = NULL;
        int i,match,found;

        found = 0;
        dprintk(KERN_DEBUG "bttv: checking video framebuffer address"
                " (%lx-%lx)\n",from,to);
        pci_for_each_dev(dev) {
                if (dev->class != PCI_CLASS_NOT_DEFINED_VGA &&
                    dev->class >> 16 != PCI_BASE_CLASS_DISPLAY)
                        continue;
                dprintk(KERN_DEBUG
                        "  pci display adapter %04x:%04x at %02x:%02x.%x\n",
                        dev->vendor,dev->device,dev->bus->number,
                        PCI_SLOT(dev->devfn),PCI_FUNC(dev->devfn));
                for (i = 0; i < DEVICE_COUNT_RESOURCE; i++) {
                        if (!(dev->resource[i].flags & IORESOURCE_MEM))
                                continue;
                        if (dev->resource[i].flags & IORESOURCE_READONLY)
                                continue;
                        match = (from >= dev->resource[i].start) &&
                                (to-1 <= dev->resource[i].end);
                        if (match)
                                found = 1;
                        dprintk(KERN_DEBUG "    memory at %08lx-%08lx%s\n",
                                dev->resource[i].start,
                                dev->resource[i].end,
                                match ? "  (check passed)" : "");
                }
        }
        return found;
}