Wednesday, September 05, 2007

Lightning Talks at Kernel Summit

Ben Herreschmidt started the lightning talks with the topic of drivers and firmware loading. The idea might be to have two suspend calls, one to enable the preloading of firmware if necessary. A GPF allocation might be blocked during a suspend, possibly holding a semaphore, which is a race that would potentially prevent a resume. Ben has had this happen to him once before. Len believes that this should be using system state, which would potentially avoid the problem. Ben also proposed pointing out a couple of drivers as good examples. Response would be to have a set of example drivers or skeleton drivers. Dave Miller pointed out that beauty is in the eye of the beholder, and others pointed out that hardware is more complex than anyone would like and that makes simple drivers hard to create. Ben redirected the context back to suspend/resume in the context of driver examples.

Dave Miller next took the podium to bring up an issue with 10 GB ethernet driver with Sun's new Neptune chip set. It supports MSIX on the PCI-Express bus. One issue would be that IRQ's could be rebalanced or rerouting all the IRQ's round robin from CPU to CPU. Arjan pointed out that the configuration for IRQ balancing doesn't move ethernet IRQ's around today. Arjan and Dave will talk more about details to make sure the infrastructure reasonably supports 10 GB ethernet capabilities appropriately.

Len Brown brought up hardware sensors and AML as a potential issue. Updating a sensor via AML might affect ACPI, such as converting a sensor from degrees celsius to degrees kelvin, leading to ACPI shutting down the machine assuming it is too hot or too cold. On Windows this doesn't seem to be an issue, but no one knows if it is because they coordinate on conventions, if they have an arbitrator, or if everyone is "just lucky". This was tabled to the mailing list.

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