On 01/08/2015 05:27 PM, Arnd Bergmann wrote:
On Thursday 08 January 2015 09:56:39 Arnd Bergmann wrote:
There is another interesting case, which is a USB host controller or
something similar behind a PCI bus. These are quite common and also
need to be handled in some form. Let's do just PCI first for now, but
be aware that this will come next. Should we assume that the ID that
is required for a device is either known from the device node, or
that it comes from a PCI device? That means for the USB case, we will
likely need to have some custom logic. There seems to be an implicit
assumption all over the kernel that all devices have the same IOMMU
instance, but we can't really rely on that here.
Update: I've checked the USB implementation and we are lucky because
these interactions are all done by the USB host controller, and a
USB device is not itself DMA capable. We don't have to do anything
for USB.
Ok Thanks.
Murali
Arnd
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Murali Karicheri
Linux Kernel, Texas Instruments
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