On Sun, 30 Sep 2001 23:07:19 +0200 (CEST), Martin Diehl wrote: > Another thing, I see some 8-10% gain in throughput when I completely > disable the mtt-delay in the irda-usb driver. This should be ok, since > irda-usb 1.0 spec requires the device to handle this by itself. My > ACT-IR200U Rev 1.00 apparently does this well. So I'm wondering whether > there are other devices requiring this or I might simply not have hit the > case where it breaks (yes, I know, all the irda-usb dongles seem to > violate the spec, at least wrt. when to apply speed changes...). > However, I have not analyzed the USB traffic - chances are the 1 msec > mtt-delay (sufficient for the OB800) is always achieved due to USB > latencies, when the newly submitted URB will not be processed before the > next USB frame starts. Comments?
The irda-usb spec is talking about the max. turnaround and the half duplex nature of the IrLAP link, and why it uses two endpoints (full duplex) for something which is half duplex traffic. This is *very* different from, and has nothing to do with the minimum turnaround time, and to imagine that the dongle should handle the min. turn time itself is beyond my imagination. There are 2 min turn times. 1) is the delay done by the irda-usb driver when switching direction from receive to transmit (given to us by the other device), and 2) is the mtt parameter we give to the other device to inform it of the delay it should use when doing the same thing. One will get better performance by reducing both, but it could however make life hard for some devices, and it could also limit the range. I'm not so sure it's a good idea to distribute a driver which doesn't follow the IrDA spec (I cannot see that the current driver cares about the mtt). It's much better that people wanting a 10% performance increase makes local changes. The problem with IrDA is usually not related to performance. It's about working at all, and range. But if things seems to work for people without using the delay, then we should probably not use it, or limit it to lets say 500us-1ms since I agree that it's bad to busy wait in the kernel. I just don't agree with the comment ;-) -- Dag > Martin > > _______________________________________________ > Linux-IrDA mailing list - [EMAIL PROTECTED] > http://www.pasta.cs.UiT.No/mailman/listinfo/linux-irda -- Dag Brattli, Mail: [EMAIL PROTECTED] CEO, ObexCode AS Web: http://www.obexcode.com Tromsoe Science Park Phone: +47 776 33 690 Forskningsparken Fax: +47 776 79 750 NO-9291 Tromsoe, NORWAY Cell: +47 481 06 352 _______________________________________________ Linux-IrDA mailing list - [EMAIL PROTECTED] http://www.pasta.cs.UiT.No/mailman/listinfo/linux-irda
