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surban / usb-gadget

Expose standard or fully custom USB peripherals (gadgets) through a USB device controller (UDC) on Linux using Rust.
https://crates.io/crates/usb-gadget
Apache License 2.0
65 stars 6 forks source link

Expand custom device example to show split mode #5

Closed samcday closed 6 months ago

samcday commented 6 months ago

By default, the example still works as it previously did.

If run with REGISTER_ONLY=1, it will pause after registering the gadget, allowing a second process to be run (which can be unprivileged) and configure FunctionFS.

samcday commented 6 months ago

I'm building a GUI app that uses usb-gadget to configure a USB gadget and drive some of it via FunctionFS. For the prototype I'm simply running the app as a privileged process, but that's obviously not shippable. I knew I'd need to split the privileged bits that poke ConfigFS into a separate binary which the GUI app spawns and controls via pkexec.

I'm really impressed that the API of this crate already perfectly supports such a use case. The only tricky part was wrapping my brain around how to actually do it. Once I got it working, I figured it might be useful to show an example of that. I imagine many users of this crate would likely benefit from applying principle of least privilege, too.

The only trade-off I see here is that the example is now more complicated and perhaps makes it harder for someone completely uninitiated to grok the basics of building a gadget with a Custom function. If you're concerned about this I'm happy to move it to a separate example file.

surban commented 6 months ago

I'm really impressed that the API of this crate already perfectly supports such a use case. The only tricky part was wrapping my brain around how to actually do it. Once I got it working, I figured it might be useful to show an example of that. I imagine many users of this crate would likely benefit from applying principle of least privilege, too.

Thanks!

The only trade-off I see here is that the example is now more complicated and perhaps makes it harder for someone completely uninitiated to grok the basics of building a gadget with a Custom function. If you're concerned about this I'm happy to move it to a separate example file.

Yes, could you do that please? It's important to keep examples simple.

samcday commented 6 months ago

:+1: I've updated it now.

surban commented 6 months ago

Thanks!