What is the correct way to indicate an unassigned PCI resource ?
Sergei Shtylyov
sshtylyov at ru.mvista.com
Tue Dec 5 01:34:38 EST 2006
Hello.
Alan wrote:
>>>Both PCI core and IDE interpret a zero length resource as unassigned.
>> This is not about 0-length resource, this is about 0-address. Look at
>>ide_hwif_confiure() in drivers/ide/setup-pci.c...
> The discussion I was having was about sl82cxx and handling unassigned
> resources. The zero address isn't relevant to that.
You were following up to the particular error message emitted by the IDE
core (which you've now deleted), so I corrected you on its reason, that's all.
>> You should know that the IRQ assumption is *not* true even for x86 since
>>IRQ0 is and has always been a perfectly valid IRQ (used by PIT).
> Please see previous million recyclings of that discussion and Linus
> answer.
When Linus remaps IRQ0 on x86, I'll follow that code as a testament. Until
this happens, I consider is just an opinion. Forcing every arch but x86 to
remap IRQ0 is an example of the double standards.
>>>Stick a real IDE resource at zero
>> > and drivers/ide can't cope.
>> Yeah, I've noticed. Unfortunately, a lot of PPC platforms (at least) are
>>doing exactly this...
> The checks need pushing upwards and removing from their current place -
> the pci layer should check the resource length, the isa pnp should I
> believe check for zero address etc.
So, it's OK to remove the base *address* check in ide_hwif_confiure()
altogether?
> libata makes a similar assumption in ata_resources_present() as someone
> (GregKH ???) needs to define what the proper way to encode "resource not
> allocated" into the PCI resources should be.
> If someone on the PCI list (cc'd) or Greg can give a definitive answer then we can go fix the
> offenders now.
Well, I thought that was IORESOURCE_UNSET...
> Alan
WBR, Sergei
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