PCI MSI: the new interrupt routing headache

[Jeff Garzik <jgarzik@pobox.com>]

I just got SATA working on Marvell.  After fixing a bunch of issues in 
the driver, the final issue was lack of interrupts.  Disabling 
CONFIG_PCI_MSI solved that, and suddenly the driver was working quite 
nicely.
The general problem is that pci_enable_msi() is not failing, on systems 
that do not support MSI.  This leads to Infiniband, tg3, and other 
drivers working around this problem by including an MSI-interrupts-work 
test during probe.
Perhaps its because I like leading edge stuff, and am playing with 
drivers for PCI MSI hardware, but it seems like I am running into this 
pci_enable_msi()-doesnt-fail problem more and more frequently.  First 
tg3, then AHCI, now sata_mv.
What needs to be done, to detect working PCI message signalled 
interrupts such that pci_enable_msi() fails properly?
Thanks,

	Jeff



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