Messages in this thread | | | From | (Eric W. Biederman) | Subject | Re: [PATCH 2/2] Initial generic hypertransport interrupt support. | Date | Tue, 11 Jul 2006 01:48:33 -0600 |
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Segher Boessenkool <segher@kernel.crashing.org> writes:
>> As for supporting multiple irqs in plain MSI mode, I don't think >> we want to do that. The problem is that multiple interrupts >> in msi mode cannot be individually routed. > > On some(/many/most) platforms that isn't a problem. Platforms > for which it is can just refuse to allocate more than one MSI > at once.
It is a problem on all platforms that currently implement MSI.
>> I think we really want >> to encourage vendors who are building cards with multiple MSI irqs >> to use MSI-X. MSI-X has a lot fewer ugly special cases and all >> architectures can individually route the irqs. > > We still should support whatever hardware already exists, if > possible.
Which hardware is this a problem for?
MSI and MSI-X only guarantee the availability of 1 irq if I recall correctly. More are a bonus so cards should be able to fall back to a single irq mode.
>> If there are interesting cards that support just MSI mode and really >> need more than one irq I would be happy to reconsider that decision >> but my impression was that plain MSI was basically not quite flexible >> enough to really be interesting, and supporting just one MSI irq was >> ok but any more would lead to all kinds of strange special cases. > > Individual drivers can deal with those special cases if they are device- > specific; and the platform can just refuse to do more than one MSI if > something platform-specific would prevent correct operation. > > It would be nice to have the MSI and MSI-X interfaces have the same > calling convention; in fact, they can probably be folded into one.
Examples? details? patches?
Part of the problem with plain MSI is that you can't mask irqs at the source, in a generic way.
How do your ideas compare with my hypertransport irq implementation?
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