1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2 3.. _gen_errors: 4 5******************* 6Generic Error Codes 7******************* 8 9 10.. _gen-errors: 11 12.. tabularcolumns:: |p{2.5cm}|p{15.0cm}| 13 14.. flat-table:: Generic error codes 15 :header-rows: 0 16 :stub-columns: 0 17 :widths: 1 16 18 19 20 - - ``EAGAIN`` (aka ``EWOULDBLOCK``) 21 22 - The ioctl can't be handled because the device is in state where it 23 can't perform it. This could happen for example in case where 24 device is sleeping and ioctl is performed to query statistics. It 25 is also returned when the ioctl would need to wait for an event, 26 but the device was opened in non-blocking mode. 27 28 - - ``EBADF`` 29 30 - The file descriptor is not a valid. 31 32 - - ``EBUSY`` 33 34 - The ioctl can't be handled because the device is busy. This is 35 typically return while device is streaming, and an ioctl tried to 36 change something that would affect the stream, or would require 37 the usage of a hardware resource that was already allocated. The 38 ioctl must not be retried without performing another action to fix 39 the problem first (typically: stop the stream before retrying). 40 41 - - ``EFAULT`` 42 43 - There was a failure while copying data from/to userspace, probably 44 caused by an invalid pointer reference. 45 46 - - ``EINVAL`` 47 48 - One or more of the ioctl parameters are invalid or out of the 49 allowed range. This is a widely used error code. See the 50 individual ioctl requests for specific causes. 51 52 - - ``ENODEV`` 53 54 - Device not found or was removed. 55 56 - - ``ENOMEM`` 57 58 - There's not enough memory to handle the desired operation. 59 60 - - ``ENOTTY`` 61 62 - The ioctl is not supported by the file descriptor. 63 64 - - ``ENOSPC`` 65 66 - On USB devices, the stream ioctl's can return this error, meaning 67 that this request would overcommit the usb bandwidth reserved for 68 periodic transfers (up to 80% of the USB bandwidth). 69 70 - - ``EPERM`` 71 72 - Permission denied. Can be returned if the device needs write 73 permission, or some special capabilities is needed (e. g. root) 74 75 - - ``EIO`` 76 77 - I/O error. Typically used when there are problems communicating with 78 a hardware device. This could indicate broken or flaky hardware. 79 It's a 'Something is wrong, I give up!' type of error. 80 81 - - ``ENXIO`` 82 83 - No device corresponding to this device special file exists. 84 85 86.. note:: 87 88 #. This list is not exhaustive; ioctls may return other error codes. 89 Since errors may have side effects such as a driver reset, 90 applications should abort on unexpected errors, or otherwise 91 assume that the device is in a bad state. 92 93 #. Request-specific error codes are listed in the individual 94 requests descriptions. 95