On 7/21/07, Roland Dreier <[email protected]> wrote:
> In a case where you have a device that which supports MSI-X (multiple
> interrupts) but the device in default is in MSI mode, ie some
> configuration change is needed on the device. In such a case, how
> would one handle between MSI-X and MSI ?
>
> ie the device initially doesn't support MSI-X
I don't understand the question really. Does the PCI spec even allow
a device to be in MSI mode by default? Surely the OS must initialize
the address/message before the device can generate an MSI?
Sorry for being not clear. What i was asking is thus:
A device that has legacy interrupts and MSI-X. I was thinking that if
MSI-X failed one should fall back to MSI mode (single message), that's
what i was assuming.
In such a case, i do enable MSI-X mode on the device, when the request
for 2 ^ n number of messages (where messages can be a max of 32), If
the request fails one falls into a single message mode, ie MSI ?
What device do you have in mind?
The device that i have in mind is a SAA7160.
I guess the interesting case is a
PCIe device that supports MSI and MSI-X but not legacy interrupts.
However I would assume such a device would come up with both MSI and
MSI-X disabled.
- R.
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