My entries in the subtarget config are ignored.
I added the following at the bottom of target/linux/x86/64/config-6.1 and built the kernel, but there is no mention of the config option in /scratch/union/build_dir/target-x86_64_musl/linux-x86_64/linux-6.1.38/.config
...
CONFIG_CRYPTO_DEV_CCP=y
CONFIG_CRYPTO_DEV_CCP_DEBUGFS=y
CRYPTO_DEV_CCP_DD=y
% grep CRYPTO_DEV_CCP /scratch/union/build_dir/target-x86_64_musl/linux-x86_64/linux-6.1.38/.config
They are set to disable in the generic config:
% i=CONFIG_CRYPTO_DEV_CCP
% grep $i target/linux/generic/config-6.1 target/linux/x86/config-6.1 target/linux/x86/64/config-6.1
target/linux/generic/config-6.1:# CONFIG_CRYPTO_DEV_CCP is not set
target/linux/generic/config-6.1:# CONFIG_CRYPTO_DEV_CCP_DEBUGFS is not set
target/linux/x86/64/config-6.1:CONFIG_CRYPTO_DEV_CCP=y
target/linux/x86/64/config-6.1:CONFIG_CRYPTO_DEV_CCP_DEBUGFS=y
EDIT: Ah!! I see, you have to hit every option relating to the symbols you want to add... I was omitting the following in my subtarget config that was set to disabled in the generic one:
CONFIG_CRYPTO_HW=y
This is complex!