Simplify hid output report handling

embassy-nrf/src/usb.rs

@@ -443,23 +443,8 @@ unsafe fn write_dma<T: Instance>(i: usize, buf: &[u8]) {
 
 impl<'d, T: Instance> driver::EndpointOut for Endpoint<'d, T, Out> {
     type ReadFuture<'a> = impl Future<Output = Result<usize, ReadError>> + 'a where Self: 'a;
-    type DataReadyFuture<'a> = impl Future<Output = ()> + 'a where Self: 'a;
 
     fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> Self::ReadFuture<'a> {
-        async move {
-            let i = self.info.addr.index();
-            assert!(i != 0);
-
-            self.wait_data_ready().await;
-
-            // Mark as not ready
-            READY_ENDPOINTS.fetch_and(!(1 << (i + 16)), Ordering::AcqRel);
-
-            unsafe { read_dma::<T>(i, buf) }
-        }
-    }
-
-    fn wait_data_ready<'a>(&'a mut self) -> Self::DataReadyFuture<'a> {
         async move {
             let i = self.info.addr.index();
             assert!(i != 0);
@@ -475,6 +460,11 @@ impl<'d, T: Instance> driver::EndpointOut for Endpoint<'d, T, Out> {
                 }
             })
             .await;
+
+            // Mark as not ready
+            READY_ENDPOINTS.fetch_and(!(1 << (i + 16)), Ordering::AcqRel);
+
+            unsafe { read_dma::<T>(i, buf) }
         }
     }
 }

embassy-usb-hid/src/async_lease.rs

@@ -1,90 +0,0 @@
-use core::cell::Cell;
-use core::future::Future;
-use core::task::{Poll, Waker};
-
-enum AsyncLeaseState {
-    Empty,
-    Waiting(*mut u8, usize, Waker),
-    Done(usize),
-}
-
-impl Default for AsyncLeaseState {
-    fn default() -> Self {
-        AsyncLeaseState::Empty
-    }
-}
-
-#[derive(Default)]
-pub struct AsyncLease {
-    state: Cell<AsyncLeaseState>,
-}
-
-pub struct AsyncLeaseFuture<'a> {
-    buf: &'a mut [u8],
-    state: &'a Cell<AsyncLeaseState>,
-}
-
-impl<'a> Drop for AsyncLeaseFuture<'a> {
-    fn drop(&mut self) {
-        self.state.set(AsyncLeaseState::Empty);
-    }
-}
-
-impl<'a> Future for AsyncLeaseFuture<'a> {
-    type Output = usize;
-
-    fn poll(
-        mut self: core::pin::Pin<&mut Self>,
-        cx: &mut core::task::Context<'_>,
-    ) -> Poll<Self::Output> {
-        match self.state.take() {
-            AsyncLeaseState::Done(len) => Poll::Ready(len),
-            state => {
-                if let AsyncLeaseState::Waiting(ptr, _, _) = state {
-                    assert_eq!(
-                        ptr,
-                        self.buf.as_mut_ptr(),
-                        "lend() called on a busy AsyncLease."
-                    );
-                }
-
-                self.state.set(AsyncLeaseState::Waiting(
-                    self.buf.as_mut_ptr(),
-                    self.buf.len(),
-                    cx.waker().clone(),
-                ));
-                Poll::Pending
-            }
-        }
-    }
-}
-
-pub struct AsyncLeaseNotReady {}
-
-impl AsyncLease {
-    pub fn new() -> Self {
-        Default::default()
-    }
-
-    pub fn try_borrow_mut<F: FnOnce(&mut [u8]) -> usize>(
-        &self,
-        f: F,
-    ) -> Result<(), AsyncLeaseNotReady> {
-        if let AsyncLeaseState::Waiting(data, len, waker) = self.state.take() {
-            let buf = unsafe { core::slice::from_raw_parts_mut(data, len) };
-            let len = f(buf);
-            self.state.set(AsyncLeaseState::Done(len));
-            waker.wake();
-            Ok(())
-        } else {
-            Err(AsyncLeaseNotReady {})
-        }
-    }
-
-    pub fn lend<'a>(&'a self, buf: &'a mut [u8]) -> AsyncLeaseFuture<'a> {
-        AsyncLeaseFuture {
-            buf,
-            state: &self.state,
-        }
-    }
-}

embassy-usb-hid/src/lib.rs

@@ -8,24 +8,21 @@
 pub(crate) mod fmt;
 
 use core::mem::MaybeUninit;
+use core::ops::Range;
 
-use async_lease::AsyncLease;
 use embassy::time::Duration;
-use embassy_usb::driver::{EndpointOut, ReadError};
+use embassy_usb::driver::EndpointOut;
 use embassy_usb::{
     control::{ControlHandler, InResponse, OutResponse, Request, RequestType},
     driver::{Driver, Endpoint, EndpointIn, WriteError},
     UsbDeviceBuilder,
 };
-use futures_util::future::{select, Either};
+
-use futures_util::pin_mut;
 #[cfg(feature = "usbd-hid")]
 use ssmarshal::serialize;
 #[cfg(feature = "usbd-hid")]
 use usbd_hid::descriptor::AsInputReport;
 
-mod async_lease;
-
 const USB_CLASS_HID: u8 = 0x03;
 const USB_SUBCLASS_NONE: u8 = 0x00;
 const USB_PROTOCOL_NONE: u8 = 0x00;
@@ -64,14 +61,12 @@ impl ReportId {
 
 pub struct State<'a, const IN_N: usize, const OUT_N: usize> {
     control: MaybeUninit<Control<'a>>,
-    lease: AsyncLease,
 }
 
 impl<'a, const IN_N: usize, const OUT_N: usize> State<'a, IN_N, OUT_N> {
     pub fn new() -> Self {
         State {
             control: MaybeUninit::uninit(),
-            lease: AsyncLease::new(),
         }
     }
 }
@@ -90,9 +85,9 @@ impl<'d, D: Driver<'d>, const IN_N: usize> HidClass<'d, D, (), IN_N> {
     /// high performance uses, and a value of 255 is good for best-effort usecases.
     ///
     /// This allocates an IN endpoint only.
-    pub fn new(
+    pub fn new<const OUT_N: usize>(
         builder: &mut UsbDeviceBuilder<'d, D>,
-        state: &'d mut State<'d, IN_N, 0>,
+        state: &'d mut State<'d, IN_N, OUT_N>,
         report_descriptor: &'static [u8],
         request_handler: Option<&'d dyn RequestHandler>,
         poll_ms: u8,
@@ -101,8 +96,7 @@ impl<'d, D: Driver<'d>, const IN_N: usize> HidClass<'d, D, (), IN_N> {
         let ep_in = builder.alloc_interrupt_endpoint_in(max_packet_size, poll_ms);
         let control = state
             .control
-            .write(Control::new(report_descriptor, None, request_handler));
+            .write(Control::new(report_descriptor, request_handler));
-
         control.build(builder, None, &ep_in);
 
         Self {
@@ -144,20 +138,14 @@ impl<'d, D: Driver<'d>, const IN_N: usize, const OUT_N: usize>
         let ep_out = builder.alloc_interrupt_endpoint_out(max_packet_size, poll_ms);
         let ep_in = builder.alloc_interrupt_endpoint_in(max_packet_size, poll_ms);
 
-        let control = state.control.write(Control::new(
+        let control = state
-            report_descriptor,
+            .control
-            Some(&state.lease),
+            .write(Control::new(report_descriptor, request_handler));
-            request_handler,
-        ));
-
         control.build(builder, Some(&ep_out), &ep_in);
 
         Self {
             input: ReportWriter { ep_in },
-            output: ReportReader {
+            output: ReportReader { ep_out, offset: 0 },
-                ep_out,
-                lease: &state.lease,
-            },
         }
     }
 
@@ -178,7 +166,21 @@ pub struct ReportWriter<'d, D: Driver<'d>, const N: usize> {
 
 pub struct ReportReader<'d, D: Driver<'d>, const N: usize> {
     ep_out: D::EndpointOut,
-    lease: &'d AsyncLease,
+    offset: usize,
+}
+
+pub enum ReadError {
+    BufferOverflow,
+    Sync(Range<usize>),
+}
+
+impl From<embassy_usb::driver::ReadError> for ReadError {
+    fn from(val: embassy_usb::driver::ReadError) -> Self {
+        use embassy_usb::driver::ReadError::*;
+        match val {
+            BufferOverflow => ReadError::BufferOverflow,
+        }
+    }
 }
 
 impl<'d, D: Driver<'d>, const N: usize> ReportWriter<'d, D, N> {
@@ -216,32 +218,56 @@ impl<'d, D: Driver<'d>, const N: usize> ReportWriter<'d, D, N> {
 }
 
 impl<'d, D: Driver<'d>, const N: usize> ReportReader<'d, D, N> {
+    /// Starts a task to deliver output reports from the Interrupt Out pipe to
+    /// `handler`.
+    pub async fn run<T: RequestHandler>(mut self, handler: &T) -> ! {
+        assert!(self.offset == 0);
+        let mut buf = [0; N];
+        loop {
+            match self.read(&mut buf).await {
+                Ok(len) => { handler.set_report(ReportId::Out(0), &buf[0..len]); }
+                Err(ReadError::BufferOverflow) => warn!("Host sent output report larger than the configured maximum output report length ({})", N),
+                Err(ReadError::Sync(_)) => unreachable!(),
+            }
+        }
+    }
+
+    /// Reads an output report from the Interrupt Out pipe.
+    ///
+    /// **Note:** Any reports sent from the host over the control pipe will be
+    /// passed to [`RequestHandler::set_report()`] for handling. The application
+    /// is responsible for ensuring output reports from both pipes are handled
+    /// correctly.
+    ///
+    /// **Note:** If `N` > the maximum packet size of the endpoint (i.e. output
+    /// reports may be split across multiple packets) and this method's future
+    /// is dropped after some packets have been read, the next call to `read()`
+    /// will return a [`ReadError::SyncError()`]. The range in the sync error
+    /// indicates the portion `buf` that was filled by the current call to
+    /// `read()`. If the dropped future used the same `buf`, then `buf` will
+    /// contain the full report.
     pub async fn read(&mut self, buf: &mut [u8]) -> Result<usize, ReadError> {
         assert!(buf.len() >= N);
 
-        // Wait until a packet is ready to read from the endpoint or a SET_REPORT control request is received
-        {
-            let data_ready = self.ep_out.wait_data_ready();
-            pin_mut!(data_ready);
-            match select(data_ready, self.lease.lend(buf)).await {
-                Either::Left(_) => (),
-                Either::Right((len, _)) => return Ok(len),
-            }
-        }
-
         // Read packets from the endpoint
         let max_packet_size = usize::from(self.ep_out.info().max_packet_size);
-        let mut total = 0;
+        let starting_offset = self.offset;
-        for chunk in buf.chunks_mut(max_packet_size) {
+        for chunk in buf[starting_offset..].chunks_mut(max_packet_size) {
             let size = self.ep_out.read(chunk).await?;
-            total += size;
+            self.offset += size;
-            if size < max_packet_size || total == N {
+            if size < max_packet_size || self.offset == N {
                 break;
             }
         }
 
+        let total = self.offset;
+        self.offset = 0;
+        if starting_offset > 0 {
+            Err(ReadError::Sync(starting_offset..total))
+        } else {
             Ok(total)
         }
+    }
 }
 
 pub trait RequestHandler {
@@ -254,10 +280,6 @@ pub trait RequestHandler {
     }
 
     /// Sets the value of report `id` to `data`.
-    ///
-    /// If an output endpoint has been allocated, output reports
-    /// are routed through [`HidClass::output()`]. Otherwise they
-    /// are sent here, along with input and feature reports.
     fn set_report(&self, id: ReportId, data: &[u8]) -> OutResponse {
         let _ = (id, data);
         OutResponse::Rejected
@@ -266,8 +288,8 @@ pub trait RequestHandler {
     /// Get the idle rate for `id`.
     ///
     /// If `id` is `None`, get the idle rate for all reports. Returning `None`
-    /// will reject the control request. Any duration above 1.020 seconds or 0
+    /// will reject the control request. Any duration at or above 1.024 seconds
-    /// will be returned as an indefinite idle rate.
+    /// or below 4ms will be returned as an indefinite idle rate.
     fn get_idle(&self, id: Option<ReportId>) -> Option<Duration> {
         let _ = id;
         None
@@ -284,7 +306,6 @@ pub trait RequestHandler {
 
 struct Control<'d> {
     report_descriptor: &'static [u8],
-    out_lease: Option<&'d AsyncLease>,
     request_handler: Option<&'d dyn RequestHandler>,
     hid_descriptor: [u8; 9],
 }
@@ -292,12 +313,10 @@ struct Control<'d> {
 impl<'a> Control<'a> {
     fn new(
         report_descriptor: &'static [u8],
-        out_lease: Option<&'a AsyncLease>,
         request_handler: Option<&'a dyn RequestHandler>,
     ) -> Self {
         Control {
             report_descriptor,
-            out_lease,
             request_handler,
             hid_descriptor: [
                 // Length of buf inclusive of size prefix
@@ -370,7 +389,7 @@ impl<'d> ControlHandler for Control<'d> {
         if let RequestType::Class = req.request_type {
             match req.request {
                 HID_REQ_SET_IDLE => {
-                    if let Some(handler) = self.request_handler.as_ref() {
+                    if let Some(handler) = self.request_handler {
                         let id = req.value as u8;
                         let id = (id != 0).then(|| ReportId::In(id));
                         let dur = u64::from(req.value >> 8);
@@ -383,25 +402,8 @@ impl<'d> ControlHandler for Control<'d> {
                     }
                     OutResponse::Accepted
                 }
-                HID_REQ_SET_REPORT => match (
+                HID_REQ_SET_REPORT => match (ReportId::try_from(req.value), self.request_handler) {
-                    ReportId::try_from(req.value),
+                    (Ok(id), Some(handler)) => handler.set_report(id, data),
-                    self.out_lease,
-                    self.request_handler.as_ref(),
-                ) {
-                    (Ok(ReportId::Out(_)), Some(lease), _) => {
-                        match lease.try_borrow_mut(|buf| {
-                            let len = buf.len().min(data.len());
-                            buf[0..len].copy_from_slice(&data[0..len]);
-                            len
-                        }) {
-                            Ok(()) => OutResponse::Accepted,
-                            Err(_) => {
-                                warn!("SET_REPORT received for output report with no reader listening.");
-                                OutResponse::Rejected
-                            }
-                        }
-                    }
-                    (Ok(id), _, Some(handler)) => handler.set_report(id, data),
                     _ => OutResponse::Rejected,
                 },
                 HID_REQ_SET_PROTOCOL => {
@@ -429,10 +431,7 @@ impl<'d> ControlHandler for Control<'d> {
             },
             (RequestType::Class, HID_REQ_GET_REPORT) => {
                 let size = match ReportId::try_from(req.value) {
-                    Ok(id) => self
+                    Ok(id) => self.request_handler.and_then(|x| x.get_report(id, buf)),
-                        .request_handler
-                        .as_ref()
-                        .and_then(|x| x.get_report(id, buf)),
                     Err(_) => None,
                 };
 
@@ -443,7 +442,7 @@ impl<'d> ControlHandler for Control<'d> {
                 }
             }
             (RequestType::Class, HID_REQ_GET_IDLE) => {
-                if let Some(handler) = self.request_handler.as_ref() {
+                if let Some(handler) = self.request_handler {
                     let id = req.value as u8;
                     let id = (id != 0).then(|| ReportId::In(id));
                     if let Some(dur) = handler.get_idle(id) {

embassy-usb/src/driver.rs

@@ -120,9 +120,6 @@ pub trait Endpoint {
 
 pub trait EndpointOut: Endpoint {
     type ReadFuture<'a>: Future<Output = Result<usize, ReadError>> + 'a
-    where
-        Self: 'a;
-    type DataReadyFuture<'a>: Future<Output = ()> + 'a
     where
         Self: 'a;
 
@@ -131,11 +128,6 @@ pub trait EndpointOut: Endpoint {
     ///
     /// This should also clear any NAK flags and prepare the endpoint to receive the next packet.
     fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> Self::ReadFuture<'a>;
-
-    /// Waits until a packet of data is ready to be read from the endpoint.
-    ///
-    /// A call to[`read()`](Self::read()) after this future completes should not block.
-    fn wait_data_ready<'a>(&'a mut self) -> Self::DataReadyFuture<'a>;
 }
 
 pub trait ControlPipe {

examples/nrf/src/bin/usb_hid.rs

@@ -52,7 +52,7 @@ async fn main(_spawner: Spawner, p: Peripherals) {
     let mut control_buf = [0; 16];
     let request_handler = MyRequestHandler {};
 
-    let mut state = State::<5, 0>::new();
+    let mut control = State::<5, 0>::new();
 
     let mut builder = UsbDeviceBuilder::new(
         driver,
@@ -66,7 +66,7 @@ async fn main(_spawner: Spawner, p: Peripherals) {
     // Create classes on the builder.
     let mut hid = HidClass::new(
         &mut builder,
-        &mut state,
+        &mut control,
         MouseReport::desc(),
         Some(&request_handler),
         60,