On Wed, 22 Sep 2004, Manoj Bhatta wrote:

> > >  but
> > > usb_get_current_frame_number() does not increase
> > > always 5 , fisrt time for some (for 45 URBs) it is
> > > same , after that it increases 5 in interval .
> > > But at one point it(usb_get_current_frame_number)
> > > increases to 10 .  some unpredictable like
> > increases
> > > 50  frames .
> 
> Why it increases unpredictably ?

It doesn't.  It increases very predictably: 1 frame per millisecond.  

What _is_ unpredictable are the times at which your driver calls 
get_current_frame_number.  Since your driver is running along with many 
other programs on the same computer, it doesn't have exclusive use of the 
CPU.  Every now and then the kernel will schedule a different process to 
run, causing your driver to have unpredictable gaps in its operation.

> > > And sometimes kernel messges "usb bandwidth would
> > have
> > > FAILED" . 
> > 
> > Don't worry about that.  It's just a warning, not an
> > error.  (And the 
> > warning is incorrect in your case.)
> > 
> > > Is there any problem in bandwidth synchronization
> > > inbetween my device driver and UHCI driver?
> > 
> > Since I don't know anything about your device
> > driver, you'll have to be 
> > the person to answer that question.
> 
> I dubgged bandwidth of UHCI when i am reading data
> from  my device . my /proc/bus/usb/devices or usbview 
> of UHCI Bandwidth tells 7392/900 (821 %) used  and
> Total number of isochronous requests: 56 .

I told you twice before, that part of the driver is broken.  The bandwidth 
calculations for isochronous transfers in the UHCI driver simply do not 
work right.  Please stop asking about it.

Alan Stern



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