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This section describes how the Qualcomm Linux kernel is integrated into the Yocto build system. It establishes a clear boundary with the Qualcomm Linux Kernel Guide — this page covers the Yocto-side integration; the Kernel Guide covers kernel development and debugging.

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Kernel recipes overview

The Linux kernel recipes used by Qualcomm Linux are in <workspace>/meta-qcom/recipes-kernel/linux. Qualcomm Linux supports the long-term support (LTS) Qualcomm Linux kernel v6.18.x. In the meta-qcom layer, there are two kernel recipes:
Kernel RecipePurpose
linux-qcom_6.18.bbBuilds the standard Qualcomm Linux kernel image.
linux-qcom-rt_6.18.bbBuilds the real-time Qualcomm Linux kernel image. Applies rt.config for real-time operation.
For the full recipe details including SRCREV, SRC_URI, and configuration fragments, see meta-qcom — Kernel recipes.

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Kernel configuration flow

The Qualcomm Linux kernel recipe uses a layered set of kernel configuration files and fragments:
VariantConfiguration and fragments files
linux-qcom_6.18.bbdefconfig, hardening.config, prune.config, qcom.config, bsp-additions.cfg
linux-qcom-rt_6.18.bbSame as above, plus rt.config
When DEBUG_BUILD=1 is set (via meta-qcom/ci/debug.yml), the following additional fragments are applied: 
KBUILD_CONFIG_EXTRA:append = " ${@oe.utils.vartrue('DEBUG_BUILD', '${S}/kernel/configs/debug.config', '', d)}"
KBUILD_CONFIG_EXTRA:append:aarch64 = " ${@oe.utils.vartrue('DEBUG_BUILD', '${S}/arch/arm64/configs/qcom_debug.config', '', d)}"
For kernel development using devtool, see Modify the Qualcomm Device Loader source using devtool and Use Yocto to develop kernel.

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Device tree integration

Device tree blobs (DTBs) and overlays (DTBOs) are packaged into a FIT image by the dtb-fit-image.bbclass class. The KERNEL_DEVICETREE variable in each machine configuration file selects which DTBs and DTBOs to include. For the full device tree integration details, including FIT_DTB_COMPATIBLE entries and FIT image generation, see meta-qcom — Include DTB and DTB overlay. For device tree development and platform device tree management, see Device Tree Architecture and Locate and Modify Device Trees in the Kernel Guide.

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Out-of-tree kernel modules

To build an out-of-tree kernel module using a Yocto recipe, see Handle out-of-tree kernel modules and device tree using recipes. Note Qualcomm Linux supports out-of-kernel device tree overlays only for the custom variant.

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Next steps