David S. Ahern wrote: > > On 04/13/2010 07:20 PM, Alexander Graf wrote: >>>>> It still needs a lot of love, but definitely an improvement from the >>>>> last version. The biggest difference for the performance boost and >>>>> stability is discovering that the usbfs in linux limits transactions to >>>>> 16k versus the EHCI spec which allows 20k per qTD. I added a hack to >>>>> submit which detects 20k requests from a guest and breaks it up into 2 >>>>> requests through the host (a 16k and then a 4k). >>>> Did someone already bring this up on LKML or wherever usbfs is >>>> discussed? Should be fixable, I naively guess. >>> I submitted the patch to linux-usb and it was nack'ed. The response was >>> that memory is allocated in powers of 2 so trying to up the limit from >>> 16k to 20k means it will actually want to find 32k of contiguous memory. >>> The suggestion was to handle it with multiple requests within qemu. I >>> guess libusb does that. >> Any reason we're not using libusb? > > Good question. I was wondering the same. I was going to look at > converting usb-linux to use libusb1 when I get some time.
Will that overcome the 16k limit or just push the split-up into libusb? Jan
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