Re: [PATCH 5/7] I/OAT: Add support for MSI and MSI-X

From: Manu Abraham
Date: Fri Jul 20 2007 - 17:59:28 EST


On 7/21/07, Nelson, Shannon <shannon.nelson@xxxxxxxxx> wrote:
Manu Abraham [mailto:abraham.manu@xxxxxxxxx]
>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.

Notice our code looks at the return from pci_enable_msix() - it will
give you a hint whether MSI-X is not supported (returns < 0) or you
simply asked for too many (returns > 0). If the former, then fallback
to legacy; if the latter, try MSI-X with only one interrupt, which
essentially emulates MSI mode.

Ok. Thanks for clearing it up. So the idea would be that if
pci_enable_msix() for "n" number of messages failed, then settle down
for 1 message, which is equivalent to MSI mode
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/