On Thu, 10 Feb 2005, David Brownell wrote:
> On Thursday 10 February 2005 12:08 pm, Alan Stern wrote:
> >
> > "Device not responding" means either that the device
> > isn't working right or that it's disconnected from the bus (or there's a
> > lot of interference on the line, or a hardware fault...). It's a
> > low-level problem. "Request timed out" means that everything is working
> > correctly at the USB protocol level, and the device simply is unable to
> > send or receive data at the current time. It's a higher-level error.
>
> But do any drivers care about that difference? None I've heard of do.
>
> And the confusion only comes up with the synchronous usb_*_msg() calls,
> since otherwise there's no ambiguity. Drivers that care about fault
> handling mostly avoid those calls anyway. (They prevent reasonable
> signal handling, blocking CTRL-C ...)
All right, I give up. How about this patch instead?
Alan Stern
===== Documentation/usb/error-codes.txt 1.15 vs edited =====
--- 1.15/Documentation/usb/error-codes.txt 2005-01-18 15:22:31 -05:00
+++ edited/Documentation/usb/error-codes.txt 2005-02-11 10:32:26 -05:00
@@ -88,13 +91,19 @@
prescribed bus turn-around time
c) unknown USB error
- In cases b) and c) either -EPROTO or -EILSEQ
- may be returned. Note that often the controller
- hardware does not distinguish among cases a),
- b), and c), so a driver cannot tell whether
- there was a protocol error, a failure to respond
- (often caused by device disconnect), or some
- other fault.
+ Note that often the controller hardware does not
+ distinguish among cases a), b), and c), so a
+ driver cannot tell whether there was a protocol
+ error, a failure to respond (often caused by
+ device disconnect), or some other fault.
+
+-ETIMEDOUT (**) No response packet received within the
prescribed
+ bus turn-around time. This error may instead be
+ reported as -EPROTO or -EILSEQ.
+
+ Note that the synchronous USB message functions
+ also use this code to indicate timeout expired
+ before the transfer completed.
-EPIPE (**) Endpoint stalled. For non-control endpoints,
reset this status with usb_clear_halt().
@@ -152,4 +161,7 @@
usb_get_*/usb_set_*():
usb_control_msg():
usb_bulk_msg():
--ETIMEDOUT timeout expired before the transfer completed
+-ETIMEDOUT Timeout expired before the transfer completed.
+ In the future this code may change to -ETIME,
+ whose definition is a closer match to this sort
+ of error.
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