On Wed, 2005-02-16 at 19:37, David Brownell wrote: > On Wednesday 16 February 2005 3:37 am, Steve Hosgood wrote: > > > > Basically, David, your suggestion of "try small URBs" works! I am now > > seeing 40 fps from my camera with URBs of 4K, 8K and 16K. > > That tells me roughly where the bug is; thanks for helping find this! > I'll ask you test a patch later on. >
Of course. No problem. A quick question if I may: someone pointed out earlier "this is linux, not windoze: there is no limit on URB size". Obviously that isn't quite true currently, but once this bug is fixed then I assume it will be. Does the USB hardware DMA-copy the contents of the incoming bulk packets straight into the URB at its correct offset? If so, and if a URB could be 2 or 3 megabytes, then my camera driver could dispense with a whole section of state machine whose current job is to construct a 2 or 3 megapixel image-buffer from many 32K URBs. Also of course, it would dispense with a boatload of memory copies and cut down the number of interrupt callbacks as well. Nevertheless, and with this current bug fixed or not, the "this is linux, not windoze: there is no limit on URB size" statement seems flawed in that the biggest buffer you can get from kmalloc() is apparently 128K. Can I get blocks bigger than that from somewhere else if I want 2 or 3Mb URBs? > > If [a new hard-disk] turns up later today then of course I'll test with > > 2.6.11-rc4 for > > you. > > > > Do you actually care any more, now that hypothesis #1 seems to have been > > correct? > > Not especially, though it'll be interesting to see if things now > act differently for you. Turning off "park" might mean the USB > throughput is slightly lower for you (there's a module parameter > that can turn it back on). > OK, well, I'll do the test RSN and tell you what happens. The disk arrived late yesterday. Not fitted yet though. Steve Hosgood. ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
