i have a custom kernel build directory (for security reason), and using KERNEL_DIR refer to it, eg. KERNEL_DIR=/path/to/kernel_build it's works fine for nvidia-drivers, but when i trying to install v4l2loopback, it just doesn't work. the Makefile in the package: ``` KERNELRELEASE ?= `uname -r` KERNEL_DIR ?= /lib/modules/$(KERNELRELEASE)/build all: v4l2loopback.ko v4l2loopback: v4l2loopback.ko v4l2loopback.ko: @echo "Building v4l2-loopback driver..." $(MAKE) -C $(KERNEL_DIR) M=$(PWD) modules ``` here is the build.log i got: ``` * v4l2loopback-0.12.5.tar.gz BLAKE2B SHA512 size ;-) ... [ ok ] * Determining the location of the kernel source code * Found kernel source directory: * /usr/src/linux-5.8.18-gentoo * Found kernel object directory: * /path/to/kernel_build * Found sources for kernel version: * 5.8.18-gentoo * Checking for suitable kernel configuration options... [ ok ] >>> Unpacking source... >>> Unpacking v4l2loopback-0.12.5.tar.gz to /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work >>> Source unpacked in /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work >>> Preparing source in /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5 ... >>> Source prepared. >>> Configuring source in /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5 ... >>> Source configured. >>> Compiling source in /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5 ... ln: failed to create symbolic link 'Module.symvers': File exists * Preparing v4l2loopback module make -j9 HOSTCC=x86_64-pc-linux-gnu-gcc CROSS_COMPILE=x86_64-pc-linux-gnu- 'LDFLAGS=-m elf_x86_64' all Building v4l2-loopback driver... make -C /usr/src/linux-5.8.18-gentoo M=/var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5 modules make[1]: Entering directory '/usr/src/linux-5.8.18-gentoo' ERROR: Kernel configuration is invalid. include/generated/autoconf.h or include/config/auto.conf are missing. Run 'make oldconfig && make prepare' on kernel src to fix it. make[1]: *** [Makefile:719: include/config/auto.conf] Error 1 make[1]: Leaving directory '/usr/src/linux-5.8.18-gentoo' make: *** [Makefile:43: v4l2loopback.ko] Error 2 * ERROR: media-video/v4l2loopback-0.12.5-r1::gentoo failed (compile phase): * emake failed * * If you need support, post the output of `emerge --info '=media-video/v4l2loopback-0.12.5-r1::gentoo'`, * the complete build log and the output of `emerge -pqv '=media-video/v4l2loopback-0.12.5-r1::gentoo'`. * The complete build log is located at '/var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/temp/build.log'. * The ebuild environment file is located at '/var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/temp/environment'. * Working directory: '/var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5' * S: '/var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5' ```
not sure why, but when i set KBUILD_OUTPUT to empty, it's compiled. logs here: ``` KERNEL_DIR=/path/to/kernel_build KBUILD_OUTPUT= ebuild /usr/portage/media-video/v4l2loopback/v4l2loopback-0.12.5-r1.ebuild clean compile[0/48400] * v4l2loopback-0.12.5.tar.gz BLAKE2B SHA512 size ;-) ... [ ok ] * Determining the location of the kernel source code * Found kernel source directory: * /usr/src/linux-5.8.18-gentoo * Found kernel object directory: * /path/to/kernel_build * Found sources for kernel version: * 5.8.18-gentoo * Checking for suitable kernel configuration options... [ ok ] >>> Unpacking source... >>> Unpacking v4l2loopback-0.12.5.tar.gz to /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work >>> Source unpacked in /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work >>> Preparing source in /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5 ... >>> Source prepared. >>> Configuring source in /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5 ... >>> Source configured. >>> Compiling source in /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5 ... ln: failed to create symbolic link 'Module.symvers': File exists * Preparing v4l2loopback module make -j9 HOSTCC=x86_64-pc-linux-gnu-gcc CROSS_COMPILE=x86_64-pc-linux-gnu- 'LDFLAGS=-m elf_x86_64' all Building v4l2-loopback driver... make -C /usr/src/linux-5.8.18-gentoo M=/var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5 modules make[1]: Entering directory '/usr/src/linux-5.8.18-gentoo' make[2]: Entering directory '/path/to/kernel_build' CC [M] /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5/v4l2loopback.o MODPOST /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5/Module.symvers CC [M] /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5/v4l2loopback.mod.o LD [M] /var/tmp/portage/media-video/v4l2loopback-0.12.5-r1/work/v4l2loopback-0.12.5/v4l2loopback.ko make[2]: Leaving directory '/path/to/kernel_build' make[1]: Leaving directory '/usr/src/linux-5.8.18-gentoo' >>> Source compiled. ```
