Re: PCI Express support for 2.4 kernel

Vladimir Kondratiev
2003-12-17T07:26:52Z

I considered it in the beginning. For device driver itself, it is not a
problem. For example, I can define
struct pcie_dev_config {
void* base;
int (*read)(pcie_dev_config* conf, unsigned reg, int len, u32* value);
int (*write)(pcie_dev_config* conf, unsigned reg, int len, u32 value);
}
and have constructor/destructor functions that use device coordinates to
calculate physical base and ioremap() it.

What you will miss, is uniform access for all devices, including those
you are not managing as PCI-E. Notable
example is bridges. I can't provide more info (see prev. mail about
brain dead, I don't want it to be my last day at work),
but you may found appropriate to tweak some stuff for bridges in
extended space. One may use /proc/bus/pci/ or 'setpci'
for this. Obviously, in this case you have no driver, and generic access
method would help you.
Also, 'lspci' don't know about device drivers, it need generic way to
access config.

And, strictly say, if it is method that replaces old one, wouldn't it
more appropriate to use it rather then rely
on backward compatibility hooks? I know, "work - don't touch", but...

Vladimir.

Jeff Garzik wrote:

> Linus Torvalds wrote:
>
>> So if this will only matter for PCI-X drivers and not for discovery
>> etc, I
>> wonder if it wouldn't make sense to have this as a totally separate
>> function? Instead of trying to make the existing "pci_config_xxxx()"
>> stuff work with PCI-X, wouldn't it be nicer to have the driver just
>> map its config space on probe?
>
>
> Not a bad idea... After posting yesterday on this thread, I had the
> thought: Just like PCI has readl() and sbus has sbus_readl(), why not
> pciex_cfg_readl() ?
>
> Any PCI-Ex drivers would obviously _know_ they are PCI Ex, and they
> could communicate that by virtue of simply using new functions. Older
> drivers for older hardware would use the old API and not care...
> Further, PCI-Ex operations are already basically readl/writel anyway,
> so going through the forest of pci_cfg_ops pointers and such would
> just add needless layering.
>
>
>> You could do it with just ioremap(), but you'd really want to
>> abstract it out a bit, and have a "[un]map_pcix_config()" function?
>
>
> Why not just work within the existing API?
> pci_{enable,disable}_device() seems fairly appropriate, as that's a
> quite clear signal of the bounds within which the driver must work.
>
> pci_enable_device() is already defined as "the PCI device's resources
> may not be available before <this> point."
>
> Jeff
>
>