On Sun, 20 Nov 2005, Stanislaw Gruszka wrote:
> Hi
>
> Usbatm need code to check correctness of both bulk and isoc
> urb. Now urb->status is used howewer it seems uhci driver
> set negative urb->status if error occurs on at least one frame,
> even if all others are ok. (This is problem for eagle ADSL usb
> modems in isoc mode, as modem produce lot frames with
> -EILSEQ error mixed with valid packets)
>
> So my question is if urb->actual_length can be used for
> check error on both isoc and bulk urbs whitout using
> conditionals for distinguish pipes, for example:
>
> if (likely(urb->actual_length > 0)) {
> /* we have good bulk urb or at least one good isoc frame */
> ...
> } else
> print_error(urb->status);
>
> I think this code will work if:
> 1) for isoc urb: urb->actual_length is equal sum actual_length of all frames
> 2) if error occurs on urb/frame - actual_length is equal 0
>
> Is 1) and 2) true?
With uhci-hcd 1) is true.
I don't understand 2). If an error occurs in a bulk or iso URB,
urb->actual_length may still be larger than 0. If an error occurs in an
iso frame, urb->frame_desc[i].actual_length may still be larger than 0 and
urb->frame_desc[i].status may still be 0 (since iso errors often are
undetectable). Does that answer your question?
Alan Stern
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