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Re: [Xen-devel] [Patch V1 2/3] xen/usb: add capability for passing through isoc jobs to host devices



On 09/09/2015 02:01 PM, Gerd Hoffmann wrote:
   Hi,

So, the signaling needs to be different.  The host adapter needs to
signal somehow that it can handle async iso packets.  One way would be
to flag this per usb bus, another one per usb packet.  Also all xen
naming and the xen inlude should go away.  BTW: does this build without
xen-devel installed?

Okay, I'll try to make it more generic. I think the async iso capability
should be a bus attribute.

Makes sense.

Can we get rid of the callbacks?  By filling the USBPacket iovec with
the iso request chunks for example?

Difficult. One iso request chunk could require multiple iovec entries.

Why multiple small iovecs instead of one big iovec?

The guest buffer might span multiple physical non contiguous pages. I
don't want to copy data to a new buffer due to performance reasons
(there is already at least one copy operation done by qemu).

usb_host_req_complete_iso_xen() returns a single status for the whole
USBPacket anyway ...

I need status per iso request, and libusb does deliver that.

The RFC version tried to avoid the callbacks and there you didn't like
exposing the additional structures.

-ENOPATCH.

Aah, sorry, my fault. I think this was part of the off-list discussion
we had.


Juergen


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