95 lines
3.2 KiB
Rust
95 lines
3.2 KiB
Rust
// server/src/usb_gadget.rs
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use std::{fs::{self, OpenOptions}, io::Write, thread, time::Duration};
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use anyhow::{Result, Context};
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use tracing::{debug, error, info, warn};
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fn wait_for_detach(udc_path: &str) {
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for _ in 0..20 {
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// as soon as the file is **empty**, the detach succeeded
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if fs::read_to_string(udc_path).map(|s| s.trim().is_empty()).unwrap_or(false) {
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debug!("🔌 UDC is now *detached*");
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return;
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}
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thread::sleep(Duration::from_millis(50));
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}
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warn!("⏳ UDC did not detach within the expected time-out");
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}
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/// Like `wait_for_detach`, but the opposite condition.
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fn wait_for_attach(udc_path: &str) {
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for _ in 0..20 {
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if fs::read_to_string(udc_path).map(|s| !s.trim().is_empty()).unwrap_or(false) {
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debug!("🔌 UDC is *attached* again");
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return;
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}
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thread::sleep(Duration::from_millis(50));
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}
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warn!("⏳ UDC did not attach within the expected time-out");
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}
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#[derive(Clone)]
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pub struct UsbGadget {
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udc_file: &'static str,
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}
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impl UsbGadget {
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pub fn new(name: &'static str) -> Self {
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// /sys/kernel/config/usb_gadget/<name>/UDC
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Self {
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udc_file: Box::leak(
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format!("/sys/kernel/config/usb_gadget/{name}/UDC").into_boxed_str(),
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),
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}
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}
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/// Force the host to re-enumerate our HID gadget.
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/// Retries on EBUSY so that a transient “resource busy” never kills the whole process.
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pub fn cycle(&self) -> Result<()> {
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info!("🔌 UDC-cycle: detaching gadget");
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OpenOptions::new()
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.write(true)
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.open(self.udc_file)?
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.write_all(b"")?; // empty string → detach
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wait_for_detach(self.udc_file);
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// Let the controller settle
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thread::sleep(Duration::from_millis(200));
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let udc_name = std::fs::read_dir("/sys/class/udc")?
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.next()
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.transpose()?
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.context("no UDC present")?
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.file_name();
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// Retry loop for the notoriously fragile re-attach
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for attempt in 0..5 {
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info!("🔌 UDC-cycle: re-attaching to {} (try #{attempt})", udc_name.to_string_lossy());
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match OpenOptions::new()
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.write(true)
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.open(self.udc_file)?
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.write_all(udc_name.to_str().unwrap().as_bytes())
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{
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Ok(()) => {
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wait_for_attach(self.udc_file);
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info!("🟢 USB-gadget cycled successfully");
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return Ok(());
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}
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Err(e) if e.raw_os_error() == Some(libc::EBUSY) => {
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warn!("🚧 UDC busy on re-attach – retrying in 100 ms");
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thread::sleep(Duration::from_millis(100));
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continue;
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}
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Err(e) => {
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error!("💥 unexpected error while re-attaching UDC: {e:?}");
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return Err(e).context("re-attaching gadget to UDC");
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}
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}
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}
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Err(anyhow::anyhow!(
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"giving up after 5 attempts – UDC remained busy"
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))
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}
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}
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