USB MSD device enable/disable within composite device

RE: USB MSD device enable/disable within composite device

Kenneth — Mon, 21 Mar 2022 12:55:06 GMT

I will ask a bit internally and let you know when I hear back. I could find this presentation that was a year ago, from the presentation it looks like they are looking into this: https://www.youtube.com/watch?v=dJ7_aRPM4Os

Kenneth

RE: USB MSD device enable/disable within composite device

dstarling — Mon, 21 Mar 2022 05:20:52 GMT

I would tend to agree with that assessment, the issue is to filter this, I'll likely have to copy the entire USB driver to be able to modify the function that updates the descriptors from static memory before output. It currently does a couple of things like fix-up the serial number field. The ability to filter descriptors likely should go in that function.
So I'll end up maintaining another custom driver outside the source tree unless I can get it adopted by Nordic/Zephyr?

RE: USB MSD device enable/disable within composite device

Kenneth — Fri, 18 Mar 2022 12:34:37 GMT

My impression is that in zephyr you add various USB class support during compile time by various config options, e.g. CONFIG_USB_MASS_STORAGE. It's not intended (or designed if you like) to dynamically adjust these run-time. So my suggestion would be inline with yours, that you need to manipulate the USB descriptors before you enable USB if you intermittently want to remove functionality. To switch configurations I suspect you need to do a softreset of the nRF52840, this will trigger the host to re-enumerate the USB device. To know which USB functionality you want to support at start of main() you may consider using the GPREGRET register (set it to a predefined value before you execute soft reset), since GPREGRET is a retained register between soft resets:
https://infocenter.nordicsemi.com/topic/ps_nrf5340/chapters/power/doc/power.html#register.GPREGRET

Best regards,
Kenneth