apl-sof-setup-audio and kernel build

[RodBarnes]

@MilkyDeveloper There is a bit of a disconnect between the build.sh/setup.sh process and then running apl-sof-setup-audio for ApolloLake devices.

For example, I can run build.sh and specify chromeos-5.15 to get that kernel version. I can then run setup.sh to get the build and flash the USB. At boot, the device is then running the 5.15.x kernel. But when apl-sof-setup-audio runs, it rebuilds the kernel and replaces it with 5.10. (Earlier, I did a PR to address this issue so I could put the new kernel in a drive location and specify that instead of it downloading the 5.10 by default.)

Yet, even with that there's still duplication. Does the inclusion of SOF firmware require it be done on the target device? Or could this be moved into the build.sh so it could be done on the build system and eliminate the duplication?

[MilkyDeveloper]

SOF firmware should be done on the target device. SOF Firmware doesn't hurt, but ideally we should only use SOF on platforms that need to run sof-setup-audio, which are not all of them (KBL/SKL). One USB should be bootable on all devices initially, so that's why I'm using this.

[RodBarnes]

I understand that SOF only applies to APL so wasn't thinking that this would happen for everyone. I was thinking that build.sh could be used -- with some kind of option setting to specify SOF -- to add the firmware and build the kernel. Then run setup.sh with the LOCAL_KERNEL feature. Since the kernel has to be built to add the SOF firmware anyway, it seems logical to do it once on the build system instead of having to do it again on the target device.

The changes would be:

1. Modify apl-sof-setup-audio to no longer add the firmware.
2. Modify build.sh to support adding SOF firmware based upon user indicating option.

Thus, for an APL device the new process would be to run build.sh to generate the kernel, then run setup.sh and specify LOCAL_KERNEL.

Let me know if this makes sense. If so, I'll proceed to go down this path and make the changes.

[MilkyDeveloper]

With all due respect - I think this would add some extra unneeded complications.

You could definitely implement this after running the script. Something like:

export ORIG_DIR=$(pwd)
bash build.sh
cd ..
bash updatekernel.sh $ORIG_DIR

# You're looking to do the parts below:
sudo mount /dev/sdX2 /mnt # Replace the X with your USB
sudo chroot /mnt /bin/bash -c "sudo apt install firmware-sof-signed -y" # Install SOF FW

Plus, if users are using the older direct-write to USB method, this is generally very slow to do on the host device.

[RodBarnes]

Hmmm... Ok, thanks for the explanation. I think I'll still dig into what apl-sof-setup-audio is doing vs build.sh -- if nothing else, so that I better understand what is going on. For now, though it still means building the kernel twice (if using other than the supplied kernel), the ability to specify a kernel path eliminates the main issue of reverting to the previous kernel when building the audio.