USB HID driver fails to recognize input devices

Julian Stecklina js at ...14...
Wed Jul 18 18:18:36 CEST 2012


what is missing for MSI support?


Udo Steinberg <udo at ...121...> wrote:

>On Wed, 18 Jul 2012 16:15:04 +0200 Sebastian Sumpf (SS) wrote:
>SS> Nevertheless there are still limitations for Nova. Because of the
>SS> number of controllers (on my box seven) the driver might discover,
>SS> PCI legacy interrupts may exhaust pretty quickly, what in return
>SS> that it is likely that no other driver that depends on PCI-IRQs
>SS> get access to them. The reason for that is that Genode does
>SS> neither support shared interrupts nor message-signaled interrupts
>SS> Nova's base platform. Also there is no IOMMU support, yet, so one
>has to
>SS> disable it when using the driver.
>Most PCI devices are only connected to one or two PCI interrupt lines.
>means you don't have much of a choice which IOAPIC pin an interrupt
>from a
>particular USB controller will signal. It is very likely that several
>those USB controllers can only drive the same PCI interrupt line.
>So you need to implement interrupt sharing or alternatively switch to
>With MSI you can give each device its dedicated interrupt vector. MSI
>is a
>mandatory feature of PCI-E, but older PCI devices may not support it.
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Sent from my phone. Please excuse my brevity.

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