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a03bede5c7
This patch (as1611) updates the USB documentation and kerneldoc to give a more precise meaning for the URB_ISO_ASAP flag and to explain more of the details of scheduling for isochronous URBs. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
174 lines
6.4 KiB
Plaintext
174 lines
6.4 KiB
Plaintext
Revised: 2004-Oct-21
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This is the documentation of (hopefully) all possible error codes (and
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their interpretation) that can be returned from usbcore.
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Some of them are returned by the Host Controller Drivers (HCDs), which
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device drivers only see through usbcore. As a rule, all the HCDs should
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behave the same except for transfer speed dependent behaviors and the
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way certain faults are reported.
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**************************************************************************
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* Error codes returned by usb_submit_urb *
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**************************************************************************
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Non-USB-specific:
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0 URB submission went fine
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-ENOMEM no memory for allocation of internal structures
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USB-specific:
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-ENODEV specified USB-device or bus doesn't exist
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-ENOENT specified interface or endpoint does not exist or
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is not enabled
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-ENXIO host controller driver does not support queuing of this type
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of urb. (treat as a host controller bug.)
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-EINVAL a) Invalid transfer type specified (or not supported)
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b) Invalid or unsupported periodic transfer interval
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c) ISO: attempted to change transfer interval
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d) ISO: number_of_packets is < 0
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e) various other cases
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-EXDEV ISO: URB_ISO_ASAP wasn't specified and all the frames
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the URB would be scheduled in have already expired.
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-EFBIG Host controller driver can't schedule that many ISO frames.
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-EPIPE The pipe type specified in the URB doesn't match the
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endpoint's actual type.
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-EMSGSIZE (a) endpoint maxpacket size is zero; it is not usable
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in the current interface altsetting.
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(b) ISO packet is larger than the endpoint maxpacket.
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(c) requested data transfer length is invalid: negative
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or too large for the host controller.
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-ENOSPC This request would overcommit the usb bandwidth reserved
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for periodic transfers (interrupt, isochronous).
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-ESHUTDOWN The device or host controller has been disabled due to some
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problem that could not be worked around.
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-EPERM Submission failed because urb->reject was set.
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-EHOSTUNREACH URB was rejected because the device is suspended.
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-ENOEXEC A control URB doesn't contain a Setup packet.
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**************************************************************************
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* Error codes returned by in urb->status *
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* or in iso_frame_desc[n].status (for ISO) *
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**************************************************************************
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USB device drivers may only test urb status values in completion handlers.
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This is because otherwise there would be a race between HCDs updating
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these values on one CPU, and device drivers testing them on another CPU.
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A transfer's actual_length may be positive even when an error has been
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reported. That's because transfers often involve several packets, so that
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one or more packets could finish before an error stops further endpoint I/O.
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For isochronous URBs, the urb status value is non-zero only if the URB is
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unlinked, the device is removed, the host controller is disabled, or the total
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transferred length is less than the requested length and the URB_SHORT_NOT_OK
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flag is set. Completion handlers for isochronous URBs should only see
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urb->status set to zero, -ENOENT, -ECONNRESET, -ESHUTDOWN, or -EREMOTEIO.
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Individual frame descriptor status fields may report more status codes.
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0 Transfer completed successfully
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-ENOENT URB was synchronously unlinked by usb_unlink_urb
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-EINPROGRESS URB still pending, no results yet
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(That is, if drivers see this it's a bug.)
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-EPROTO (*, **) a) bitstuff error
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b) no response packet received within the
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prescribed bus turn-around time
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c) unknown USB error
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-EILSEQ (*, **) a) CRC mismatch
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b) no response packet received within the
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prescribed bus turn-around time
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c) unknown USB error
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Note that often the controller hardware does not
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distinguish among cases a), b), and c), so a
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driver cannot tell whether there was a protocol
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error, a failure to respond (often caused by
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device disconnect), or some other fault.
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-ETIME (**) No response packet received within the prescribed
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bus turn-around time. This error may instead be
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reported as -EPROTO or -EILSEQ.
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-ETIMEDOUT Synchronous USB message functions use this code
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to indicate timeout expired before the transfer
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completed, and no other error was reported by HC.
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-EPIPE (**) Endpoint stalled. For non-control endpoints,
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reset this status with usb_clear_halt().
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-ECOMM During an IN transfer, the host controller
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received data from an endpoint faster than it
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could be written to system memory
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-ENOSR During an OUT transfer, the host controller
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could not retrieve data from system memory fast
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enough to keep up with the USB data rate
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-EOVERFLOW (*) The amount of data returned by the endpoint was
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greater than either the max packet size of the
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endpoint or the remaining buffer size. "Babble".
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-EREMOTEIO The data read from the endpoint did not fill the
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specified buffer, and URB_SHORT_NOT_OK was set in
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urb->transfer_flags.
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-ENODEV Device was removed. Often preceded by a burst of
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other errors, since the hub driver doesn't detect
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device removal events immediately.
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-EXDEV ISO transfer only partially completed
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(only set in iso_frame_desc[n].status, not urb->status)
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-EINVAL ISO madness, if this happens: Log off and go home
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-ECONNRESET URB was asynchronously unlinked by usb_unlink_urb
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-ESHUTDOWN The device or host controller has been disabled due
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to some problem that could not be worked around,
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such as a physical disconnect.
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(*) Error codes like -EPROTO, -EILSEQ and -EOVERFLOW normally indicate
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hardware problems such as bad devices (including firmware) or cables.
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(**) This is also one of several codes that different kinds of host
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controller use to indicate a transfer has failed because of device
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disconnect. In the interval before the hub driver starts disconnect
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processing, devices may receive such fault reports for every request.
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**************************************************************************
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* Error codes returned by usbcore-functions *
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* (expect also other submit and transfer status codes) *
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**************************************************************************
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usb_register():
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-EINVAL error during registering new driver
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usb_get_*/usb_set_*():
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usb_control_msg():
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usb_bulk_msg():
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-ETIMEDOUT Timeout expired before the transfer completed.
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