[ipxe-devel] SAN Boot Windows XP with USB-NIC.

Michael Brown mbrown at fensystems.co.uk
Thu Mar 10 23:21:44 UTC 2011

On Thursday 10 Mar 2011 23:04:59 Muralidhar.Appalla at emulex.com wrote:
> Yes, our device supports IRQ. This information that is populated from UNDI
>  is directly read from PCI Configuration space and populated. But we do not
>  enable interrupts in our UNDI stack but rather do polling. Our OS drivers
>  definitely use this IRQ.
> The statement to check whether IRQ is zero seems to me also very safe to
>  do.

Sorry, I think I'm misunderstanding something.  You say that the information 
provided in UNDI is directly read from PCI configuration space, in which case 
it *will* include a non-zero IRQ number.  That means that if I apply the 
following logic:

> > i.e. assume that the NIC supports interrupts if *either* the ServiceFlags
> > indicate SUPPORTED_IRQ *or* the IRQ number is non-zero.

then that would cause iPXE to assume that your UNDI driver *does* generate 
interrupts, and so it will fail.

It sounds as though this idea (to assume that the NIC supports interrupts if 
either the ServiceFlags indicate SUPPORTED_IRQ or the IRQ number is non-zero) 
would *break* iPXE running over the Emulex UNDI stack.

Am I missing something?


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