g_mass_storage issues in 4.9 kernel

Question

I previously had the Mass Storage gadget mainly working with the April version of Jessie (kernel 4.4.50+). Unfortunately it wasn't working on all systems so I thought it would be worth updating to see if a new kernel would work.

I did an apt-get upgrade but that failed to boot. I then did a fresh Jessie Lite install (4.9.35+, July 2017).

I then went through the usual setup process

$ echo "dtoverlay=dwc2" | sudo tee -a /boot/config.txt

no problems after reboot

$ echo "dwc2" | sudo tee -a /etc/module

no problems after reboot

$ echo "g_mass_storage" | sudo tee -a /etc/modules

kernel panic on boot - happened everytime

I managed to regain access by manually altering config.txt on the SD card to comment out the dwc2 overlay. This let me get back into the system. I then did an rpi-update to 4.9.36+, however this then had the same issue when I re-enabled the dwc2 overlay (this is presumably why my apt-get upgrade version ran into issues)

Does anyone have any ideas what has changed that is stopping this from now working? Unfortunately as I can't get SSH access when it crashes on boot I can't paste the full kernel panic dump (unless it's stored somewhere in a log I can access on next successful boot??)

Answer 1

OK so if I boot with dtoverlay in config.txt and dwc2 in /etc/module set then try to manually start g_mass_storage with sudo modprobe … then it seems to work, in a way that starting it in /etc/modules caused a crash.

I don't quite understand what has changed (given the previous system worked fine with the older kernel), but at least it seems to load with the latest Jessie Lite now!