Dan Streetman wrote: > Aha, thanks for finding that. For a bit of background, that was added > because the signal-based notification of URBs never worked (or at > least, not when I was trying to make it work). So hence, the polling > loop was added, and the FIXME comment. The reason it uses 0 is > because back then, when the kernel had a hardcoded 10ms scheduler > interval, any sleep was guaranteed at least 10ms of downtime. > However, later kernels change that to much smaller intervals, and in > some cases the scheduler is not even timer-based, so the assumption no > longer applies. > > The reason for the counter to 20 is because when there are many URBs > piling up in the kernel waiting for javax.usb to read them, we don't > want to sleep, as that will greatly reduce throughput. So the > 20-count was added to only sleep when there really was nothing > happening on the USB bus. > > Modified patch (using only 10000) is applied in CVS, thanks. > If usleep works as it should now, should we not reduce the sleep to 1000 (1ms) and just loop once for each sleep? Well, perhaps twice to reduce a slight buildup of lag. I think I will try with 1ms here where the processing of the sent commands takes a few ms. With the original C code the communication would look like this (H->host, D->device): (H) Send command. (H) Ready yet? (D) No. (H) Ready yet? (D) No. (H) Ready yet? (D) No. (H) Ready yet? (D) Yes. Where the ready yet would be issued several times. With Javax.usb it would almost always look like: (H) Send command. (H) Ready yet? (D) Yes.
Since often Send command and ready yet would be processed between different sleeps. For sending / receiving data this is not noticeable, but with query response it could be seen. Also, in order to compile I changed: Index: jni/JavaxUsbKernel.h =================================================================== RCS file: /cvsroot/javax-usb/javax-usb-ri-linux/jni/JavaxUsbKernel.h,v retrieving revision 1.5 diff -r1.5 JavaxUsbKernel.h 16d15 < 19c18 < #include <linux/usb.h> --- > #include <linux/usb/ch9.h> I'll report how this goes. //Roger Lindsjö ------------------------------------------------------------------------- SF.Net email is sponsored by: The Future of Linux Business White Paper from Novell. From the desktop to the data center, Linux is going mainstream. Let it simplify your IT future. http://altfarm.mediaplex.com/ad/ck/8857-50307-18918-4 _______________________________________________ javax-usb-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/javax-usb-devel
