Re: pci_check_type2() help.

[Onkar N Mahajan <kernzap@gmail.com>]

On Mon, 2012-04-16 at 12:13 -0700, Randy Dunlap wrote: 
> On 04/16/2012 09:02 AM, Onkar N Mahajan wrote:
> 
> > Hello list, 
> > 
> > I am trying to understand the PCI functionality in Linux kernel. 
> > What is the best way to start to understanding this - where to start 
> > in the kernel code ? Books ? Manuals ? 
> > 
> > I started reading the code - where I am stuck in this function -
> > pci_check_type2() ; Wherein I am not able to get from where these values
> > 0xCFB,0xCF8,0xCFA are arrived at ? I guess these are port numbers , but 
> > in which manuals can I find this all information. 
> > 
> > linux/arch/x86/pci/init.c: 
> > static int __init pci_check_type2(void)
> > {
> >     unsigned long flags;
> >     int works = 0;
> > 
> >     local_irq_save(flags);
> > 
> >     outb(0x00, 0xCFB);
> >     outb(0x00, 0xCF8);
> >     outb(0x00, 0xCFA);
> >     if (inb(0xCF8) == 0x00 && inb(0xCFA) == 0x00 &&
> >         pci_sanity_check(&pci_direct_conf2)) {
> >         works = 1;
> >     }
> > 
> >     local_irq_restore(flags);
> > 
> >     return works;
> > }
> > 
> > 
> > Please help me figuring out right manuals for this. 
> 
> 
> The PCI spec (version 2.1 seems to be all I have available)
> discusses PCI Configuration Mechanisms and Special Cycles and
> these PCI config registers.
> 
Thanks Randy , for your help. Can you please also guide me with 
respect to good way to start understanding the PCI implementation 
in Linux ?

-- Onkar