Re: Latest 2.4 IA64 Baseline (Bjorn) + Latest ACPI testing report

From: Matthew Wilcox <>
Date: 2003-12-17 23:23:20
On Wed, Dec 17, 2003 at 10:54:09AM +0800, Yu, Luming wrote:
> >> I think  "To bus device, resources returned from _CRS method means that bus device will
> >> supply those resouces to its children devices. So it's unreasonable to call
> >> request_resource for them."
> >That's faulty logic.  Resources can either be busy (used at the leaf
> >by a driver) or merely containers for other resources (as they are in
> >this case).
> My concern is that if a device driver want to request a resource,
> but that resource has been allocated by bus device (which supply this resources to its children devices) 
> then  -EBUSY get returned. Maybe device driver can
> ignore this error.  But how to detect a real resource conflict  with other device (another resource consumer)?  All of them return -EBUSY.

No, you don't understand how resources work.  When device drivers request
them, they're marked as busy.  When busses claim them, they're marked
as not-busy.  Take a look at __request_region in kernel/resource.c.
It checks IORESOURCE_BUSY to see whether it can have the new resource
as a child of the existing one.

> > For example, when
> >PCI needs to allocate resources, if we don't partition the root resource
> >amongst the child busses, we could inadvertently allocate resources that
> >straddle two PCI busses, and that just won't work.
> All resources info returned from _CRS has been saved in pci_root_info->controller->window.  Is it enough?

No, the generic PCI code knows nothing about this ACPI-specific
information.  It relies on the resources being set up correctly.

"Next the statesmen will invent cheap lies, putting the blame upon 
the nation that is attacked, and every man will be glad of those
conscience-soothing falsities, and will diligently study them, and refuse
to examine any refutations of them; and thus he will by and by convince 
himself that the war is just, and will thank God for the better sleep 
he enjoys after this process of grotesque self-deception." -- Mark Twain
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Received on Wed Dec 17 07:23:36 2003

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