Re: Problem with ioremap which returns NULL in 2.6 kernel

["Richard B. Johnson" <root@chaos.analogic.com>]

On Wed, 2 Jun 2004, Markus Lidel wrote:

> Hello,
>
> Jeff Garzik wrote:
> >>>>>My preferred approach would be:  consider that the hardware does not
> >>>>>need the entire 0x8000000-byte area mapped.  Plain and simple.
> >>>>>This is a "don't do that" situation, and that renders the other
> >>>>>questions moot :)  You should only be mapping what you need to map.
> >>>>Okay, i'll let try it out with only 64MB.
> >>>Why do you need 64MB, even?  :)
> >>I don't know how much space i need :-D But why does the device set the
> >>size to 128MB then?
> > Devices often export things you don't care about, such as direct access
> > to internal chip RAM.
> > Look through the driver that figure out the maximum value that the
> > driver actually _uses_.  There is no need to guess.
>
> Okay, i've looked at it, but i don't think i could simply use less
> space, because (if i understand the I2O spec right :-D) the controller
> returns me a address inside this window, where i could write the I2O
> message. So i ask the controller, where do you want my request, then he
> tells me a address...
>
> If i only ioremap 64MB, and the controller tells me write at 80MB, i'm
> in deep trouble :-D
>
> >> 	size = dev->resource[i].end-dev->resource[i].start+1;
> > You should be using pci_resource_start() and pci_resource_len()
> > to obtain this information.
>
> Yep, thanks, but a patch for this is already send :-)
>
> Best regards,
>

I2O, as seen from the PCI/Bus, is a bus! Right? You have a
PCI/Bus controller that provides for an interface into
I2O? Right? Can you do `cat /proc/pci` and show what device
you think it is?  I think you are attempting to access a bridge
or something. I2O is supposed to be intelligent and to grab
64 megabytes of host address space is the anthesis of this.

Cheers,
Dick Johnson
Penguin : Linux version 2.4.26 on an i686 machine (5570.56 BogoMips).
            Note 96.31% of all statistics are fiction.