How to link configuration to os_descs?

[mrschyte]

Is there a way to link a configuration to os_desc?

Normally I'd issue ln -s configs/c.1/ os_desc in the gadget configfs folder, but I'd like to do this with a gadget-tool schema if possible.

I've tried specifying the os_descs multiple ways, but gt never seems to link the config.

[pabs3]

I don't think I understand the code fully, but from a quick glance; in libusbgx, symlink() from libc is called with os_desc, from usbg_create_os_desc_link(), from usbg_set_os_desc_config(), from usbg_import_gadget_os_descs(), from usbg_import_gadget_run(), from usbg_import_gadget(), from load_func() in gt. So in theory this symlink should be happening already if the config has the right string. So there could be a bug, or the config might be incorrect. I note there is an example in the example systemd README.md, if something like that doesn't work then it is likely a bug that someone will need to figure out.

[mrschyte]

Thanks for looking into this. Unfortunately, I've already tried with the linked example to no avail. The descriptors do get set, however the symlink is missing, so they're not applied to the configuration. Currently I'm just running ln manually after gt load. I'll try running strace/ltrace to see if symlink is called at all.

[pabs3]

I expect the ltrace output would be useful, as would a minimal example of how to reproduce the problem using dummy_hcd on a laptop. https://www.collabora.com/news-and-blog/blog/2019/06/24/using-dummy-hcd/

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-- bye, pabs https://bonedaddy.net/pabs3/

[mrschyte]

I couldn't get ltrace working (I'm running this on a Raspberry Pi and it's throwing an error for some reason). I did verify using gdb that symlink is not called for linking the config under os_descs. I'll try setting up dummy-hcd.

[mrschyte]

Please find the traces and the gadget scheme file here: https://gist.github.com/mrschyte/d9de2ff6ad95157ff43bc55fec618621

[pabs3]

Not sure when I will have time to look at this, but please note that RNDIS is apparently an insecure protocol so you may want to drop it.