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Revised: 2004-Oct-21
This is the documentation of (hopefully) all possible error codes (and
their interpretation) that can be returned from usbcore.
Some of them are returned by the Host Controller Drivers (HCDs), which
device drivers only see through usbcore. As a rule, all the HCDs should
behave the same except for transfer speed dependent behaviors and the
way certain faults are reported.
**************************************************************************
* Error codes returned by usb_submit_urb *
**************************************************************************
Non-USB-specific:
0 URB submission went fine
-ENOMEM no memory for allocation of internal structures
USB-specific:
-ENODEV specified USB-device or bus doesn't exist
-ENOENT specified interface or endpoint does not exist or
is not enabled
-ENXIO host controller driver does not support queuing of this type
of urb. (treat as a host controller bug.)
-EINVAL a) Invalid transfer type specified (or not supported)
b) Invalid or unsupported periodic transfer interval
c) ISO: attempted to change transfer interval
d) ISO: number_of_packets is < 0
e) various other cases
-EAGAIN a) specified ISO start frame too early
b) (using ISO-ASAP) too much scheduled for the future
wait some time and try again.
-EFBIG Host controller driver can't schedule that many ISO frames.
-EPIPE The pipe type specified in the URB doesn't match the
endpoint's actual type.
-EMSGSIZE (a) endpoint maxpacket size is zero; it is not usable
in the current interface altsetting.
(b) ISO packet is larger than the endpoint maxpacket.
(c) requested data transfer length is invalid: negative
or too large for the host controller.
-ENOSPC This request would overcommit the usb bandwidth reserved
for periodic transfers (interrupt, isochronous).
-ESHUTDOWN The device or host controller has been disabled due to some
problem that could not be worked around.
-EPERM Submission failed because urb->reject was set.
-EHOSTUNREACH URB was rejected because the device is suspended.
-ENOEXEC A control URB doesn't contain a Setup packet.
**************************************************************************
* Error codes returned by in urb->status *
* or in iso_frame_desc[n].status (for ISO) *
**************************************************************************
USB device drivers may only test urb status values in completion handlers.
This is because otherwise there would be a race between HCDs updating
these values on one CPU, and device drivers testing them on another CPU.
A transfer's actual_length may be positive even when an error has been
reported. That's because transfers often involve several packets, so that
one or more packets could finish before an error stops further endpoint I/O.
For isochronous URBs, the urb status value is non-zero only if the URB is
unlinked, the device is removed, the host controller is disabled, or the total
transferred length is less than the requested length and the URB_SHORT_NOT_OK
flag is set. Completion handlers for isochronous URBs should only see
urb->status set to zero, -ENOENT, -ECONNRESET, -ESHUTDOWN, or -EREMOTEIO.
Individual frame descriptor status fields may report more status codes.
0 Transfer completed successfully
-ENOENT URB was synchronously unlinked by usb_unlink_urb
-EINPROGRESS URB still pending, no results yet
(That is, if drivers see this it's a bug.)
-EPROTO (*, **) a) bitstuff error
b) no response packet received within the
prescribed bus turn-around time
c) unknown USB error
-EILSEQ (*, **) a) CRC mismatch
b) no response packet received within the
prescribed bus turn-around time
c) unknown USB error
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.
-ETIME (**) No response packet received within the prescribed
bus turn-around time. This error may instead be
reported as -EPROTO or -EILSEQ.
-ETIMEDOUT Synchronous USB message functions use this code
to indicate timeout expired before the transfer
completed, and no other error was reported by HC.
-EPIPE (**) Endpoint stalled. For non-control endpoints,
reset this status with usb_clear_halt().
-ECOMM During an IN transfer, the host controller
received data from an endpoint faster than it
could be written to system memory
-ENOSR During an OUT transfer, the host controller
could not retrieve data from system memory fast
enough to keep up with the USB data rate
-EOVERFLOW (*) The amount of data returned by the endpoint was
greater than either the max packet size of the
endpoint or the remaining buffer size. "Babble".
-EREMOTEIO The data read from the endpoint did not fill the
specified buffer, and URB_SHORT_NOT_OK was set in
urb->transfer_flags.
-ENODEV Device was removed. Often preceded by a burst of
other errors, since the hub driver doesn't detect
device removal events immediately.
-EXDEV ISO transfer only partially completed
(only set in iso_frame_desc[n].status, not urb->status)
-EINVAL ISO madness, if this happens: Log off and go home
-ECONNRESET URB was asynchronously unlinked by usb_unlink_urb
-ESHUTDOWN The device or host controller has been disabled due
to some problem that could not be worked around,
such as a physical disconnect.
(*) Error codes like -EPROTO, -EILSEQ and -EOVERFLOW normally indicate
hardware problems such as bad devices (including firmware) or cables.
(**) This is also one of several codes that different kinds of host
controller use to indicate a transfer has failed because of device
disconnect. In the interval before the hub driver starts disconnect
processing, devices may receive such fault reports for every request.
**************************************************************************
* Error codes returned by usbcore-functions *
* (expect also other submit and transfer status codes) *
**************************************************************************
usb_register():
-EINVAL error during registering new driver
usb_get_*/usb_set_*():
usb_control_msg():
usb_bulk_msg():
-ETIMEDOUT Timeout expired before the transfer completed.
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