Adding udev package in Buildroot

I am trying to add udev package in Buildroot and have added the following config parameter in the defconfig file:

./configs/xxx_dev_defconfig:BR2_PACKAGE_HAS_UDEV=y

However, I cannot see the above config option is added in the final .config file after doing make xxx_dev_defconfig. I noticed the BR2_PACKAGE_HAS_UDEV is set in the previous project in the following locations:

./output/build/buildroot-config/autoconf.h:#define BR2_PACKAGE_HAS_UDEV 1
./output/build/buildroot-config/auto.conf:BR2_PACKAGE_HAS_UDEV=y

These look like autogenerated files which are are preset in the current project as well but BR2_PACKAGE_HAS_UDEV is missing there. How do I make this BR2_PACKAGE_HAS_UDEV config option a part of the auto-generated conf file?

Edit:

After doing a bit of faffing around I think I have a temporary solution. In my make menuconfig-> Target packages -> Hardware handling the package option eudev seems to be not select-able. And it says, " eudev needs eudev /dev management ".

So I looked into the following menuconfig options under System Configuration -> /dev management:

Inside the /dev management I have to select "Dynamic using devtmpfs + eudev" as below:

instead of:

Once I do that then I go back to the following menu option:

Inside that I go to Hardware handling:

Now I can see eudev option which I can select:

You cannot set the BR2_PACKAGE_HAS_UDEV option manually. It's a so-called blind option, it can only be enabled by a select statement in one of the user-visible options.

In this case, there are two ways to enable it:

• select systemd as the init system (BR2_INIT_SYSTEMD);
• select any other init system and select devtmpfs + eudev as /dev management (BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_EUDEV).