Hi USB list,
I've a little problem, but I'm not able to find a solution...
I've a generic custom USB device with several end points.
One of them (a bulk one) is read periodically (polled, 64 byte) every
second. There was some time inconsistencies, so I checked the USB
traffic with a sniffer, and I discovered that transactions are compacted
at the start of the loop in a block of 64 read (64 byte * 64 msg = 4096
byte). In other words, on the bus the first read is followed immediately
by the next 63 read.
I guess that this is a pre-fetch optimization for BULK end points. How
can I disable this optimization for this end point? How can I come back
to a more "real-time" behavior? I tried to play with open() flags
(O_NONBLOCK, O_DIRECT) without luck.
Using FreeBSD 7 with HPS stack, this behavior didn't happen. Every read
consists in 1 read on the bus and everything is fine.
Thanks in advance!
Luca
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