Re: [Linux-usb-users] USB: Non zero status

On Sun, 26 Aug 2007, Martin Bachem wrote:

> Alan Stern schrieb:
> > You'll probably still need to do the "start_frame" debugging to figure
> > out the reason for those -EXDEV errors, though.
> 
> by now I received a logfile with printk's of the start_frame values:
> 
> kernel: ISO_FRAME_START_DEBUG fifo(5) urb(0) (6) -
> kernel:  159975656 159975672 159975688 159975704 159975720 159975736
> 159975496 159975512 159975528 159975544 159975560 159975576 159975592
> 159975608 159975624 159975640
> kernel: HFC-S USB: rx_iso_complete with -EXDEV urb->status -18, fifo(5)
> kernel: HFC-S USB: rx_iso_complete ISO packet 4, status: -18
> kernel: HFC-S USB: rx_iso_complete ISO packet 5, status: -18
> kernel: HFC-S USB: rx_iso_complete ISO packet 6, status: -18
> 
> This output is done according to my patch at
> http://git.misdn.org/?p=mISDN.git;a=commit;h=4cf360765203d6c1e6bb407fc42f36a6c35bcac2
> 
> Above you see the printk of one ISO URBs has completed with -EXDEV. The
> start_frame history of this URB is seamlessly. This URBs completes every
> 16 USB Frames. At interval of 1 ms, 8 packets each URB, 2 URBs for this
> endpoint (alternating completions). The other URB serving this endpoint
> had no -EXDEV.
> 
> Now the target system is running an hcd-uhci version with your uhci-q
> patch, I'll let you know if -EXDEV still occures, or if it's solved...

It's still mystifying.  Oh well, let's see what happens with the patch.  
Keep your start_frame debugging code installed.

There's one other thing you should know.  Recently I sent in a separate
patch which also affects Iso URB status codes in uhci-hcd.  You don't
need to worry about it now, because it won't be merged until 2.6.24,
but you should realize it is coming.  What it does is leave urb->status
equal to 0 even when some of the individual iso_frame_desc statuses
have an error code.  This means your driver won't be able to rely on
urb->status for Iso error checking; it will have to look at each frame
descriptor.

Alan Stern


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