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