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aic8800d80/OPENWRT.md
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Shen Mintao eef3d25ca4 fix: select monitor-channel callback from cfg80211 header type
Keep the internal monitor-channel API independent of kernel versions and select a correctly typed cfg80211 adapter at compile time. This covers Ubuntu 6.8.0-147 and stable/backports without release-string heuristics or function-pointer casts.

Validation: reproduced the original failure on Ubuntu 6.8.0-147; all three modules build on 6.8.0-146, 6.8.0-147 and 6.17.0-14. Fixes #107.
2026-10-19 11:32:32 +08:00

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# Building with OpenWrt backports
OpenWrt's target kernel and wireless stack can have different versions.
For example, [issue #94](https://github.com/shenmintao/aic8800d80/issues/94)
uses Linux **6.12.94** with **backports 6.18.26** on OpenWrt 25.12.5.
The Ubuntu build host's kernel version is not used to select these APIs.
## Package Makefile
Pass `CFG80211_VERSION=6.18.26` to the kernel make invocation for that
combination. Use the `PKG_VERSION` from your OpenWrt
`package/kernel/mac80211/Makefile`, in `major.minor.patch` format. Keep the
backports include paths and symbol versions from the same build:
```make
NOSTDINC_FLAGS := \
$(KERNEL_NOSTDINC_FLAGS) \
-I$(STAGING_DIR)/usr/include/mac80211-backport/uapi \
-I$(STAGING_DIR)/usr/include/mac80211-backport \
-I$(STAGING_DIR)/usr/include/mac80211/uapi \
-I$(STAGING_DIR)/usr/include/mac80211 \
-include backport/backport.h
define Build/Compile
+$(KERNEL_MAKE) $(PKG_JOBS) \
M="$(PKG_BUILD_DIR)/drivers/aic8800" \
KBUILD_EXTRA_SYMBOLS="$(LINUX_DIR)/../symvers/mac80211.symvers" \
NOSTDINC_FLAGS="$(NOSTDINC_FLAGS)" \
CFG80211_VERSION=6.18.26 \
modules
endef
```
The package must depend on `kmod-cfg80211` so its headers and symbol versions
are staged before this driver is built. Keep any additional dependencies,
firmware installation rules and module packaging rules your device needs.
Update the package's pinned source revision to one containing this fix, or
apply the fix as an OpenWrt package patch, then clean and rebuild the package:
```sh
make package/kernel/aic8800d80/clean
make package/kernel/aic8800d80/compile V=sc -j1
```
Changing `CFG80211_VERSION` alone does not update the driver source or the
wireless headers. The value must match the actual wireless stack; do not set
it to the host kernel version or redefine `LINUX_VERSION_CODE`.
## Compatibility scope
The override selects the wireless API changes since Linux 6.12, including
radio/link arguments, radar notifications and newer cfg80211 callbacks.
The monitor-channel callback is selected from the actual cfg80211 header type
so distribution backports also work without changing the version override.
Timer, USB, memory-management and module namespace
checks continue to use the target kernel version. Older target kernels with
newer backports may need additional wireless API adaptations.
Leave `CFG80211_VERSION` unset when building against the kernel's own wireless
stack, as on a regular Ubuntu/Debian installation. The driver then uses the
kernel version as before. Hardware revision still determines whether to use
`main` or `legacy-mcu1`; a wireless API mismatch does not change that choice.
The feeds/Kconfig duplicate definitions and recursive dependencies also
reported in issue #94 belong to the OpenWrt build configuration and require
separate investigation.
See the [build regression recipe](tests/openwrt-backports/README.md) for
the tested kernel/backports combinations and a script to repeat the build.