libcamera-mchp: ipa_microchip_isc.so fails to load due to undefined symbol calculateAdaptiveExposure()

[DNTT-1603]

I found an issue when running mchpcam-still with libcamera-mchp on Microchip Buildroot.
The IPA shared object fails to load because of an undefined symbol:

[root@sam9x75curiosity ~]$ mchpcam-still 
Requested resolution: 1920x1080
[0:01:03.876751800] [209]  INFO Camera camera_manager.cpp:313 libcamera v0.3.1
[0:01:03.964183400] [210] ERROR IPAModule ipa_module.cpp:422 ipa_microchip_isc.so: Failed to open IPA module shared object: /usr/lib/libcamera/ipa_microchip_isc.so: undefined symbol: _ZNK9libcamera3ipa13microchip_isc3AGC25calculateAdaptiveExposureEf
[0:01:03.964597000] [210] ERROR IPAManager ipa_manager.h:43 Failed to load proxy
[0:01:03.964989800] [210] ERROR MicrochipISC microchip-isc.cpp:624 Failed to load AWB IPA module
No cameras available

After checking the source code, I found that this symbol appears to be referenced, but I could not find a definition for the corresponding function:

uint32_t calculateAdaptiveExposure(float brightness) const

Environment:

• buildroot-mchp: linux4microchip-2025.10
• buildroot-external-microchip: linux4microchip-2025.10

Could you please confirm whether this function is expected to be provided elsewhere, or whether its implementation is actually missing from the current source code?
Thanks

[Balki01]

Hi @DNTT-1603,

Thanks for the detailed report and for tracking this down — it's much appreciated.

AGC::calculateAdaptiveExposure() was declared in agc.h and called in three fallback paths inside interpolateExposure() but had no implementation, leaving an undefined symbol in ipa_microchip_isc.so. On your target, libcamera v0.3.1 dlopen() likely uses RTLD_NOW, which resolves all symbols eagerly at load time — causing the IPA module to fail to load entirely and resulting in no cameras being detected.
In our case, dlopen() uses RTLD_LAZY, deferring resolution until the symbol is actually called. Since these are fallback paths not exercised during normal IMX219 operation, it passed undetected on our end.
Please find the fix attached as a patch. You can apply it to your local tree and verify:

git am 0001-ipa-microchip-isc-Add-calculateAdaptiveExposure-impl.patch
make libcamera-mchp-rebuild

Once validated from our end, the fix will be pushed to the libcamera-mchp-2025.10 branch. Thank you again and please feel free to reach out if you run into anything further.

0001-ipa-microchip-isc-Add-calculateAdaptiveExposure-impl.patch