I want to be able to use a different CS pin for SPI9. For instance, if I wanted to make GPIO26 the CS for SPI9 instead. I see the DTS files in kernel/msm-3.18/arch/arm/boot/dts/qcom/msmcobalt-pinctrl.dtsi and others. How do I replace just the DTB on a VOXL unit? Or do I need to rebuild the whole kernel and replace the kernel as a whole?

@Alex-Kushleyev

So I have a BMI088 plugged in there, so I was adding IMU4 to not lose support for MPU as well. However, I did as you suggest as a sanity check, and yes I can see it trying to clock. I must have a problem somewhere else, thank you this was very helpful.

I have modified apq8096-imu-server to add another IMU, which is going to be connected to J7, using SPI (BLSP9). However, when I try and talk to this device in my code, I can see on my scope no activity. Is there something additional I need to do?
I've modified:
common/voxl_imu_server.h - updated N_IMUS, added my IMU as IMU4
server/src/imu_interface.c - Added my IMU to imu_ic_t , added it to switch statements, etc
server/src/config_file.c - added IMU4 config entries

And of course implemented my code as per the existing IMUs. I am passing it as bus 9, as I believe this is supposed to map to BLSP9. But I cannot see anything being clocked, chip selects changing, etc...