Re: [PATCH 4/25] msi: Simplify msi enable and disable.

[ebiederm@xmission.com (Eric W. Biederman)]

Rajesh Shah <rajesh.shah@intel.com> writes:

> On Tue, Jun 20, 2006 at 04:28:17PM -0600, Eric W. Biederman wrote:
>> 
>> @@ -937,27 +936,8 @@ int pci_enable_msi(struct pci_dev* dev)
>>  	if (!pos)
>>  		return -EINVAL;
>>  
>> -	if (!msi_lookup_vector(dev, PCI_CAP_ID_MSI)) {
>> -		/* Lookup Sucess */
>> -		unsigned long flags;
>> +	BUG_ON(!msi_lookup_vector(dev, PCI_CAP_ID_MSI));
>>  
> A driver that calls pci_enable_msi() while MSI is already enabled
> will hit this BUG_ON. This is different from the behavior of
> some other pci functions like pci_enable_device(), which
> silently return success if the requested operation is a nop.
> It's pretty easy to do the same here too (ditto for MSI-X).

With MSI-X we can't be a NOOP so it is clearly a bug.

With MSI it might happen, and I don't have a problem if it becomes
a noop.  At the same time I'm not convinced it isn't a bug.

All I really care about is that we don't try and do the impossible and
enable the msi from a half initialized software state like we were doing
before.

That was really ugly and impossible to get right.

Eric
-
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