2024-09-09 08:52:07 +00:00
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<title>Generic Error Codes</title>
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<table frame="none" pgwide="1" id="gen-errors">
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<title>Generic error codes</title>
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<tgroup cols="2">
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&cs-str;
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<tbody valign="top">
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<!-- Keep it ordered alphabetically -->
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2024-09-09 08:57:42 +00:00
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<row>
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<entry>EAGAIN (aka EWOULDBLOCK)</entry>
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<entry>The ioctl can't be handled because the device is in state where
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it 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.
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It is also returned when the ioctl would need to wait
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for an event, but the device was opened in non-blocking mode.
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</entry>
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</row>
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2024-09-09 08:52:07 +00:00
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<row>
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<entry>EBADF</entry>
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<entry>The file descriptor is not a valid.</entry>
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</row>
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<row>
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<entry>EBUSY</entry>
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<entry>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 the
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usage of a hardware resource that was already allocated. The ioctl
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must not be retried without performing another action to fix the
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problem first (typically: stop the stream before retrying).</entry>
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</row>
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<row>
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<entry>EFAULT</entry>
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<entry>There was a failure while copying data from/to userspace,
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probably caused by an invalid pointer reference.</entry>
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</row>
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<row>
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<entry>EINVAL</entry>
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<entry>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 individual
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ioctl requests for specific causes.</entry>
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</row>
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<row>
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<entry>ENODEV</entry>
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<entry>Device not found or was removed.</entry>
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</row>
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<row>
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<entry>ENOMEM</entry>
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<entry>There's not enough memory to handle the desired operation.</entry>
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</row>
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<row>
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<entry>ENOTTY</entry>
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<entry>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.</entry>
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</row>
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<row>
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<entry>ENOSPC</entry>
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<entry>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
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for periodic transfers (up to 80% of the USB bandwidth).</entry>
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</row>
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<row>
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<entry>EPERM</entry>
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<entry>Permission denied. Can be returned if the device needs write
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permission, or some special capabilities is needed
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(e. g. root)</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>Note 1: ioctls may return other error codes. Since errors may have side
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effects such as a driver reset, applications should abort on unexpected errors.
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</para>
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<para>Note 2: Request-specific error codes are listed in the individual
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requests descriptions.</para>
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