usb: simplify buffer handling for Control IN transfers.

embassy-usb/src/control.rs

@@ -131,6 +131,13 @@ pub enum OutResponse {
     Rejected,
 }
 
+#[derive(Copy, Clone, Eq, PartialEq, Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub enum InResponse {
+    Accepted(usize),
+    Rejected,
+}
+
 /// A trait for implementing USB classes.
 ///
 /// All methods are optional callbacks that will be called by
@@ -171,54 +178,7 @@ pub trait ControlHandler {
     ///
     /// * `req` - The request from the SETUP packet.
     /// * `control` - The control pipe.
-    fn control_in<'a>(&mut self, req: Request, control: ControlIn<'a>) -> InResponse<'a> {
-        control.reject()
-    }
-}
-
-/// Handle for a control IN transfer. When implementing a class, use the methods of this object to
-/// response to the transfer with either data or an error (STALL condition). To ignore the request
-/// and pass it on to the next class, call [`Self::ignore()`].
-pub struct ControlIn<'a> {
-    buf: &'a mut [u8],
-}
-
-#[derive(Eq, PartialEq, Debug)]
-#[cfg_attr(feature = "defmt", derive(defmt::Format))]
-pub struct InResponse<'a> {
-    pub(crate) response: OutResponse,
-    pub(crate) data: &'a [u8],
-}
-
-impl<'a> InResponse<'a> {
-    pub fn status(&self) -> OutResponse {
-        self.response
-    }
-}
-
-impl<'a> ControlIn<'a> {
-    pub(crate) fn new(buf: &'a mut [u8]) -> Self {
-        ControlIn { buf }
-    }
-
-    /// Accepts the transfer with the supplied buffer.
-    pub fn accept(self, data: &[u8]) -> InResponse<'a> {
-        assert!(data.len() < self.buf.len());
-
-        let buf = &mut self.buf[0..data.len()];
-        buf.copy_from_slice(data);
-
-        InResponse {
-            response: OutResponse::Accepted,
-            data: buf,
-        }
-    }
-
-    /// Rejects the transfer by stalling the pipe.
-    pub fn reject(self) -> InResponse<'a> {
-        InResponse {
-            response: OutResponse::Rejected,
-            data: &[],
-        }
+    fn control_in(&mut self, req: Request, resp: &mut [u8]) -> InResponse {
+        InResponse::Rejected
     }
 }

embassy-usb/src/lib.rs

@@ -278,7 +278,6 @@ impl<'d, D: Driver<'d>> UsbDevice<'d, D> {
                 _ => self.control.reject(),
             },
             (RequestType::Class, Recipient::Interface) => {
-                let mut buf = [0; 128];
                 let handler = self
                     .interfaces
                     .iter_mut()
@@ -286,10 +285,10 @@ impl<'d, D: Driver<'d>> UsbDevice<'d, D> {
                     .map(|(_, h)| h);
                 match handler {
                     Some(handler) => {
-                        let resp = handler.control_in(req, ControlIn::new(&mut buf));
-                        match resp.response {
-                            OutResponse::Accepted => self.control.accept_in(resp.data).await,
-                            OutResponse::Rejected => self.control.reject(),
+                        let mut buf = [0; 128];
+                        match handler.control_in(req, &mut buf) {
+                            InResponse::Accepted(len) => self.control.accept_in(&buf[..len]).await,
+                            InResponse::Rejected => self.control.reject(),
                         }
                     }
                     None => self.control.reject(),

examples/nrf/src/bin/usb/cdc_acm.rs

@@ -3,7 +3,7 @@ use core::mem::{self, MaybeUninit};
 use core::sync::atomic::{AtomicBool, Ordering};
 use defmt::info;
 use embassy::blocking_mutex::CriticalSectionMutex;
-use embassy_usb::control::{self, ControlHandler, ControlIn, InResponse, OutResponse, Request};
+use embassy_usb::control::{self, ControlHandler, InResponse, OutResponse, Request};
 use embassy_usb::driver::{Endpoint, EndpointIn, EndpointOut, ReadError, WriteError};
 use embassy_usb::{driver::Driver, types::*, UsbDeviceBuilder};
 
@@ -120,20 +120,19 @@ impl ControlHandler for Control {
         }
     }
 
-    fn control_in<'a>(&mut self, req: Request, control: ControlIn<'a>) -> InResponse<'a> {
+    fn control_in(&mut self, req: Request, resp: &mut [u8]) -> InResponse {
         match req.request {
             // REQ_GET_ENCAPSULATED_COMMAND is not really supported - it will be rejected below.
             REQ_GET_LINE_CODING if req.length == 7 => {
                 info!("Sending line coding");
                 let coding = self.shared().line_coding.lock(|x| x.get());
-                let mut data = [0; 7];
-                data[0..4].copy_from_slice(&coding.data_rate.to_le_bytes());
-                data[4] = coding.stop_bits as u8;
-                data[5] = coding.parity_type as u8;
-                data[6] = coding.data_bits;
-                control.accept(&data)
+                resp[0..4].copy_from_slice(&coding.data_rate.to_le_bytes());
+                resp[4] = coding.stop_bits as u8;
+                resp[5] = coding.parity_type as u8;
+                resp[6] = coding.data_bits;
+                InResponse::Accepted(7)
             }
-            _ => control.reject(),
+            _ => InResponse::Rejected,
         }
     }
 }