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SubjectRe: [PATCH] USB: ftdi_sio: Remove tty->low_latency.
Date
Am Dienstag, 17. November 2009 19:35:07 schrieb Eric W. Biederman:
> Boiled down. ftdi_chars_in_buffer is essentially
> priv->tx_outstanding_bytes. tx_outstanding_bytes is incremented when an
> urb request is sent and tx_outstanding_bytes is decremented when an urb
> request completes.
>
> It turns out I have a moderately noisy usb line, and so I occasionally
> get messages like:
>
> ehci_hcd 0000:00:0a.1: detected XactErr len 0/7 retry 31
>
> Which as best as I can tell result in the urb getting abandoned and
> neither completed nor canceled (because we have hit the maximum
> retry count and they still don't succeed).

The URB should be finished with an error code in urb->status.
ftdi_write_bulk_callback() does decrement the counter even in
the error case.

> Which appears to result in tx_outstanding_bytes getting stuck at
> some positive number.

Do you see this message

if (status) {
dbg("nonzero write bulk status received: %d", status);
return;
}

if you enable debugging output?

Regards
Oliver



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