pci_alloc_msi error

[John Baldwin]

On Thursday, December 08, 2011 8:56:39 pm lixin.pang at emc.com wrote:
> I'm writing a PCI device driver for freebsd 7.3.  In the driver attach 
function,
> 
> pci_enable_busmaster(dev) returns 0,
> 
> pci_msi_count(dev) returns 1,
> 
> however, error = pci_alloc_msi(dev, &msi) failed with error == 6 (device not 
configured).

I assume you set msi to 1 before you called it?  (It is both an input and 
output parameter.)

> Am I missing any steps before calling pci_alloc_msi?

I don't believe so.  The reasons I see that pci_alloc_msi() will fail with 
ENXIO are:

- the driver has allocated its INTx IRQ via bus_alloc_resource() of rid 0
  of the SYS_RES_IRQ type
- the driver has already allocated MSI or MSI-X IRQs
- MSI is blacklisted for the system or for a parent PCI-PCI bridge
- APIC mode is disabled or your system has an unsupported CPU (only
  Intel, AMD, and certain VIA CPUs are known to work, other CPUs
  might work, we just haven't heard of it).
- The system is completely out of MSI IRQ tokens (there are 512 of
  these, so this is doubtful)

-- 
John Baldwin