From a402aa6f33576e20ac3420000e4bbb469a927e0f Mon Sep 17 00:00:00 2001
From: Philipp Schuster <phip1611@gmail.com>
Date: Sun, 23 Aug 2026 12:18:24 +0200
Subject: [PATCH] uefi-raw: pack USB descriptor structs

The USB 2.0 specification defines all standard descriptors with 1-byte
packing, and EDK2 declares EFI_USB_*_DESCRIPTOR inside #pragma pack(1)
accordingly [0]. With natural repr(C) layout, ConfigDescriptor was 10
bytes (spec: 9) and EndpointDescriptor 8 bytes (spec: 7) due to the
u16 member; DeviceRequest and DeviceDescriptor deviated in alignment
only.

[0]: https://github.com/tianocore/edk2/blob/7735ed4f8eb3afaf1a97d27a8862f382c387f0bc/MdePkg/Include/IndustryStandard/Usb.h#L85
---
 uefi-raw/CHANGELOG.md            |  3 +++
 uefi-raw/src/protocol/usb/mod.rs | 35 +++++++++++++++++++++++++++-----
 2 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/uefi-raw/CHANGELOG.md b/uefi-raw/CHANGELOG.md
index 3b656954..500c78a3 100644
--- a/uefi-raw/CHANGELOG.md
+++ b/uefi-raw/CHANGELOG.md
@@ -5,6 +5,9 @@
 ## Changed
 - **Breaking**: `MemoryDescriptor` now has a new member to ensure correct
   layout on all non-UEFI 32-bit targets.
+- **Breaking**: The USB descriptor types in `protocol::usb` are now packed to
+  match their layout in the USB specification. `ConfigDescriptor` and
+  `EndpointDescriptor` previously had a too-large `size_of`.
 
 ## Removed
 
diff --git a/uefi-raw/src/protocol/usb/mod.rs b/uefi-raw/src/protocol/usb/mod.rs
index 42aa9574..013c9171 100644
--- a/uefi-raw/src/protocol/usb/mod.rs
+++ b/uefi-raw/src/protocol/usb/mod.rs
@@ -18,7 +18,7 @@ newtype_enum! {
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
-#[repr(C)]
+#[repr(C, packed)]
 pub struct DeviceRequest {
     pub request_type: u8,
     pub request: u8,
@@ -27,6 +27,11 @@ pub struct DeviceRequest {
     pub length: u16,
 }
 
+// Compile-time ABI check.
+const _: () = {
+    assert!(size_of::<DeviceRequest>() == 8);
+};
+
 bitflags! {
     #[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
     #[repr(transparent)]
@@ -55,7 +60,7 @@ pub type AsyncUsbTransferCallback = unsafe extern "efiapi" fn(
 ) -> Status;
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
-#[repr(C)]
+#[repr(C, packed)]
 pub struct DeviceDescriptor {
     pub length: u8,
     pub descriptor_type: u8,
@@ -73,8 +78,13 @@ pub struct DeviceDescriptor {
     pub num_configurations: u8,
 }
 
+// Compile-time ABI check.
+const _: () = {
+    assert!(size_of::<DeviceDescriptor>() == 18);
+};
+
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
-#[repr(C)]
+#[repr(C, packed)]
 pub struct ConfigDescriptor {
     pub length: u8,
     pub descriptor_type: u8,
@@ -86,8 +96,13 @@ pub struct ConfigDescriptor {
     pub max_power: u8,
 }
 
+// Compile-time ABI check.
+const _: () = {
+    assert!(size_of::<ConfigDescriptor>() == 9);
+};
+
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
-#[repr(C)]
+#[repr(C, packed)]
 pub struct InterfaceDescriptor {
     pub length: u8,
     pub descriptor_type: u8,
@@ -100,8 +115,13 @@ pub struct InterfaceDescriptor {
     pub interface: u8,
 }
 
+// Compile-time ABI check.
+const _: () = {
+    assert!(size_of::<InterfaceDescriptor>() == 9);
+};
+
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
-#[repr(C)]
+#[repr(C, packed)]
 pub struct EndpointDescriptor {
     pub length: u8,
     pub descriptor_type: u8,
@@ -110,3 +130,8 @@ pub struct EndpointDescriptor {
     pub max_packet_size: u16,
     pub interval: u8,
 }
+
+// Compile-time ABI check.
+const _: () = {
+    assert!(size_of::<EndpointDescriptor>() == 7);
+};