From 56da5a2c575b71d20c35a62f3a5c94bbcfc97f30 Mon Sep 17 00:00:00 2001
From: bae <73325521+baeuric@users.noreply.github.com>
Date: Mon, 29 May 2023 17:59:17 -0700
Subject: [PATCH] fix(embassy-usb): Make BOS descriptor optional

---
 embassy-usb/src/builder.rs | 21 ++++++++++++++-------
 embassy-usb/src/lib.rs     | 15 ++++++++++-----
 2 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/embassy-usb/src/builder.rs b/embassy-usb/src/builder.rs
index 6b68bcd7..9f263626 100644
--- a/embassy-usb/src/builder.rs
+++ b/embassy-usb/src/builder.rs
@@ -131,7 +131,7 @@ pub struct Builder<'d, D: Driver<'d>> {
 
     device_descriptor: DescriptorWriter<'d>,
     config_descriptor: DescriptorWriter<'d>,
-    bos_descriptor: BosWriter<'d>,
+    bos_descriptor: Option<BosWriter<'d>>,
 
     #[cfg(feature = "msos-descriptor")]
     msos_descriptor: MsOsDescriptorWriter<'d>,
@@ -148,7 +148,7 @@ impl<'d, D: Driver<'d>> Builder<'d, D> {
         config: Config<'d>,
         device_descriptor_buf: &'d mut [u8],
         config_descriptor_buf: &'d mut [u8],
-        bos_descriptor_buf: &'d mut [u8],
+        bos_descriptor_buf: Option<&'d mut [u8]>,
         #[cfg(feature = "msos-descriptor")] msos_descriptor_buf: &'d mut [u8],
         control_buf: &'d mut [u8],
     ) -> Self {
@@ -170,11 +170,13 @@ impl<'d, D: Driver<'d>> Builder<'d, D> {
 
         let mut device_descriptor = DescriptorWriter::new(device_descriptor_buf);
         let mut config_descriptor = DescriptorWriter::new(config_descriptor_buf);
-        let mut bos_descriptor = BosWriter::new(DescriptorWriter::new(bos_descriptor_buf));
+        let mut bos_descriptor = bos_descriptor_buf.map(|buf| BosWriter::new(DescriptorWriter::new(buf)));
 
         device_descriptor.device(&config);
         config_descriptor.configuration(&config);
-        bos_descriptor.bos();
+        if let Some(descriptor) = bos_descriptor.as_mut() {
+            descriptor.bos();
+        }
 
         Builder {
             driver,
@@ -199,12 +201,16 @@ impl<'d, D: Driver<'d>> Builder<'d, D> {
         let msos_descriptor = self.msos_descriptor.build(&mut self.bos_descriptor);
 
         self.config_descriptor.end_configuration();
-        self.bos_descriptor.end_bos();
+        if let Some(descriptor) = self.bos_descriptor.as_mut() {
+            descriptor.end_bos();
+        }
 
         // Log the number of allocator bytes actually used in descriptor buffers
         info!("USB: device_descriptor used: {}", self.device_descriptor.position());
         info!("USB: config_descriptor used: {}", self.config_descriptor.position());
-        info!("USB: bos_descriptor used: {}", self.bos_descriptor.writer.position());
+        if let Some(descriptor) = self.bos_descriptor.as_ref() {
+            info!("USB: bos_descriptor used: {}", descriptor.writer.position());
+        }
         #[cfg(feature = "msos-descriptor")]
         info!("USB: msos_descriptor used: {}", msos_descriptor.len());
         info!("USB: control_buf size: {}", self.control_buf.len());
@@ -215,7 +221,8 @@ impl<'d, D: Driver<'d>> Builder<'d, D> {
             self.handlers,
             self.device_descriptor.into_buf(),
             self.config_descriptor.into_buf(),
-            self.bos_descriptor.writer.into_buf(),
+            self.bos_descriptor
+                .map(|descriptor| descriptor.writer.into_buf() as &[u8]),
             self.interfaces,
             self.control_buf,
             #[cfg(feature = "msos-descriptor")]
diff --git a/embassy-usb/src/lib.rs b/embassy-usb/src/lib.rs
index d8563d59..796c95be 100644
--- a/embassy-usb/src/lib.rs
+++ b/embassy-usb/src/lib.rs
@@ -173,7 +173,9 @@ pub struct UsbBufferReport {
     /// Number of config descriptor bytes used
     pub config_descriptor_used: usize,
     /// Number of bos descriptor bytes used
-    pub bos_descriptor_used: usize,
+    ///
+    /// Will be `None` if "bos_descriptor_buf" was not supplied to builder
+    pub bos_descriptor_used: Option<usize>,
     /// Number of msos descriptor bytes used
     ///
     /// Will be `None` if the "msos-descriptor" feature is not active.
@@ -196,7 +198,7 @@ struct Inner<'d, D: Driver<'d>> {
     config: Config<'d>,
     device_descriptor: &'d [u8],
     config_descriptor: &'d [u8],
-    bos_descriptor: &'d [u8],
+    bos_descriptor: Option<&'d [u8]>,
 
     device_state: UsbDeviceState,
     suspended: bool,
@@ -224,7 +226,7 @@ impl<'d, D: Driver<'d>> UsbDevice<'d, D> {
         handlers: Vec<&'d mut dyn Handler, MAX_HANDLER_COUNT>,
         device_descriptor: &'d [u8],
         config_descriptor: &'d [u8],
-        bos_descriptor: &'d [u8],
+        bos_descriptor: Option<&'d [u8]>,
         interfaces: Vec<Interface, MAX_INTERFACE_COUNT>,
         control_buf: &'d mut [u8],
         #[cfg(feature = "msos-descriptor")] msos_descriptor: crate::msos::MsOsDescriptorSet<'d>,
@@ -269,7 +271,7 @@ impl<'d, D: Driver<'d>> UsbDevice<'d, D> {
         UsbBufferReport {
             device_descriptor_used: self.inner.device_descriptor.len(),
             config_descriptor_used: self.inner.config_descriptor.len(),
-            bos_descriptor_used: self.inner.bos_descriptor.len(),
+            bos_descriptor_used: self.inner.bos_descriptor.map(|descriptor| descriptor.len()),
             msos_descriptor_used: mdu,
             control_buffer_size: self.control_buf.len(),
         }
@@ -726,7 +728,10 @@ impl<'d, D: Driver<'d>> Inner<'d, D> {
         let (dtype, index) = req.descriptor_type_index();
 
         match dtype {
-            descriptor_type::BOS => InResponse::Accepted(self.bos_descriptor),
+            descriptor_type::BOS => match self.bos_descriptor {
+                Some(descriptor) => InResponse::Accepted(descriptor),
+                None => InResponse::Rejected,
+            },
             descriptor_type::DEVICE => InResponse::Accepted(self.device_descriptor),
             descriptor_type::CONFIGURATION => InResponse::Accepted(self.config_descriptor),
             descriptor_type::STRING => {