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:

-EBUSY The URB is already active.

-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

-EXDEV ISO: URB_ISO_ASAP wasn't specified and all the frames

the URB would be scheduled in have already expired.

-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.