Complete Yocto mirror with license table for TQMa6UL (2038-compliance)
- 264 license table entries with exact download URLs (224/264 resolved) - Complete sources/ directory with all BitBake recipes - Build configuration: tqma6ul-multi-mba6ulx, spaetzle (musl) - Full traceability for Softwarefreigabeantrag - GCC 13.4.0, Linux 6.6.102, U-Boot 2023.04, musl 1.2.4 - License distribution: GPL-2.0 (24), MIT (23), GPL-2.0+ (18), BSD-3 (16)
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sources/poky/documentation/dev-manual/device-manager.rst
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sources/poky/documentation/dev-manual/device-manager.rst
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.. SPDX-License-Identifier: CC-BY-SA-2.0-UK
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.. _device-manager:
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Selecting a Device Manager
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**************************
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The Yocto Project provides multiple ways to manage the device manager
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(``/dev``):
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- Persistent and Pre-Populated ``/dev``: For this case, the ``/dev``
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directory is persistent and the required device nodes are created
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during the build.
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- Use ``devtmpfs`` with a Device Manager: For this case, the ``/dev``
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directory is provided by the kernel as an in-memory file system and
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is automatically populated by the kernel at runtime. Additional
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configuration of device nodes is done in user space by a device
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manager like ``udev`` or ``busybox-mdev``.
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Using Persistent and Pre-Populated ``/dev``
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===========================================
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To use the static method for device population, you need to set the
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:term:`USE_DEVFS` variable to "0"
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as follows::
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USE_DEVFS = "0"
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The content of the resulting ``/dev`` directory is defined in a Device
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Table file. The
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:term:`IMAGE_DEVICE_TABLES`
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variable defines the Device Table to use and should be set in the
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machine or distro configuration file. Alternatively, you can set this
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variable in your ``local.conf`` configuration file.
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If you do not define the :term:`IMAGE_DEVICE_TABLES` variable, the default
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``device_table-minimal.txt`` is used::
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IMAGE_DEVICE_TABLES = "device_table-mymachine.txt"
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The population is handled by the ``makedevs`` utility during image
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creation:
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Using ``devtmpfs`` and a Device Manager
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=======================================
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To use the dynamic method for device population, you need to use (or be
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sure to set) the :term:`USE_DEVFS`
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variable to "1", which is the default::
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USE_DEVFS = "1"
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With this
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setting, the resulting ``/dev`` directory is populated by the kernel
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using ``devtmpfs``. Make sure the corresponding kernel configuration
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variable ``CONFIG_DEVTMPFS`` is set when building you build a Linux
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kernel.
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All devices created by ``devtmpfs`` will be owned by ``root`` and have
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permissions ``0600``.
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To have more control over the device nodes, you can use a device manager like
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``udev`` or ``busybox-mdev``. You choose the device manager by defining the
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:term:`VIRTUAL-RUNTIME_dev_manager <VIRTUAL-RUNTIME>` variable in your machine
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or distro configuration file. Alternatively, you can set this variable in
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your ``local.conf`` configuration file::
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VIRTUAL-RUNTIME_dev_manager = "udev"
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# Some alternative values
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# VIRTUAL-RUNTIME_dev_manager = "busybox-mdev"
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# VIRTUAL-RUNTIME_dev_manager = "systemd"
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