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+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+
+.. _gen_errors:
+
+*******************
+Generic Error Codes
+*******************
+
+
+.. _gen-errors:
+
+.. tabularcolumns:: |p{2.5cm}|p{15.0cm}|
+
+.. flat-table:: Generic error codes
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 16
+
+
+ - - ``EAGAIN`` (aka ``EWOULDBLOCK``)
+
+ - The ioctl can't be handled because the device is in state where it
+ can't perform it. This could happen for example in case where
+ device is sleeping and ioctl is performed to query statistics. It
+ is also returned when the ioctl would need to wait for an event,
+ but the device was opened in non-blocking mode.
+
+ - - ``EBADF``
+
+ - The file descriptor is not a valid.
+
+ - - ``EBUSY``
+
+ - The ioctl can't be handled because the device is busy. This is
+ typically return while device is streaming, and an ioctl tried to
+ change something that would affect the stream, or would require
+ the usage of a hardware resource that was already allocated. The
+ ioctl must not be retried without performing another action to fix
+ the problem first (typically: stop the stream before retrying).
+
+ - - ``EFAULT``
+
+ - There was a failure while copying data from/to userspace, probably
+ caused by an invalid pointer reference.
+
+ - - ``EINVAL``
+
+ - One or more of the ioctl parameters are invalid or out of the
+ allowed range. This is a widely used error code. See the
+ individual ioctl requests for specific causes.
+
+ - - ``ENODEV``
+
+ - Device not found or was removed.
+
+ - - ``ENOMEM``
+
+ - There's not enough memory to handle the desired operation.
+
+ - - ``ENOTTY``
+
+ - The ioctl is not supported by the driver, actually meaning that
+ the required functionality is not available, or the file
+ descriptor is not for a media device.
+
+ - - ``ENOSPC``
+
+ - On USB devices, the stream ioctl's can return this error, meaning
+ that this request would overcommit the usb bandwidth reserved for
+ periodic transfers (up to 80% of the USB bandwidth).
+
+ - - ``EPERM``
+
+ - Permission denied. Can be returned if the device needs write
+ permission, or some special capabilities is needed (e. g. root)
+
+ - - ``EIO``
+
+ - I/O error. Typically used when there are problems communicating with
+ a hardware device. This could indicate broken or flaky hardware.
+ It's a 'Something is wrong, I give up!' type of error.
+
+ - - ``ENXIO``
+
+ - No device corresponding to this device special file exists.
+
+
+.. note::
+
+ #. This list is not exhaustive; ioctls may return other error codes.
+ Since errors may have side effects such as a driver reset,
+ applications should abort on unexpected errors, or otherwise
+ assume that the device is in a bad state.
+
+ #. Request-specific error codes are listed in the individual
+ requests descriptions.