From f6bb61ba189ae233645e4aa3901aa303d134a694 Mon Sep 17 00:00:00 2001
From: Antoine Reversat <a.reversat@gmail.com>
Date: Thu, 7 May 2026 14:05:13 -0400
Subject: [PATCH] Move report descriptor parsing into usbhid

---
 drivers/input/usbhidd/Cargo.toml   |  2 +
 drivers/input/usbhidd/src/descs.rs | 88 ++++++++++++++++++++++++++++++
 drivers/input/usbhidd/src/main.rs  | 12 ++--
 3 files changed, 97 insertions(+), 5 deletions(-)
 create mode 100644 drivers/input/usbhidd/src/descs.rs

diff --git a/drivers/input/usbhidd/Cargo.toml b/drivers/input/usbhidd/Cargo.toml
index 2c0cda1915..05bef7d12d 100644
--- a/drivers/input/usbhidd/Cargo.toml
+++ b/drivers/input/usbhidd/Cargo.toml
@@ -13,8 +13,10 @@ anyhow.workspace = true
 bitflags.workspace = true
 log.workspace = true
 orbclient.workspace = true
+plain.workspace = true
 redox_syscall.workspace = true
 rehid = { git = "https://gitlab.redox-os.org/redox-os/rehid.git" }
+smallvec.workspace = true
 xhcid = { path = "../../usb/xhcid" }
 
 common = { path = "../../common" }
diff --git a/drivers/input/usbhidd/src/descs.rs b/drivers/input/usbhidd/src/descs.rs
new file mode 100644
index 0000000000..dddd00b39d
--- /dev/null
+++ b/drivers/input/usbhidd/src/descs.rs
@@ -0,0 +1,88 @@
+use anyhow::{Result, anyhow};
+use plain::Plain;
+use smallvec::SmallVec;
+use std::convert::TryInto;
+
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, Default)]
+pub enum HidClassType {
+    #[default]
+    HID = 0x21,
+    Report,
+    Physical
+}
+
+#[repr(C, packed)]
+#[derive(Clone, Copy, Debug, Default)]
+pub struct HidClassDescriptor {
+    pub desc_type: HidClassType,
+    pub desc_len: u16,
+}
+
+unsafe impl Plain for HidClassDescriptor {}
+
+#[derive(Clone, Debug, Default)]
+pub struct HidDescriptor {
+    pub length: u8,
+    pub kind: u8,
+    pub hid_spec_release: u16,
+    pub country_code: u8,
+    pub num_descriptors: u8,
+    pub descriptors: SmallVec<[HidClassDescriptor; 1]>,
+}
+
+impl HidDescriptor {
+    // Size of the fixed part of HidDescriptor
+    const HID_DESC_FIXED_SIZE: u8 = 6;
+    const HID_CLASS_DESC_SIZE: u8 = 3;
+
+    pub fn from_bytes(bytes: &[u8]) -> Result<Self> {
+        let length = bytes[0];
+        let kind = bytes[1];
+
+        // A valid descriptor has at least one class descriptor
+        if (length < Self::HID_DESC_FIXED_SIZE + Self::HID_CLASS_DESC_SIZE) {
+            return Err(anyhow!("Invalid length"));
+        }
+
+        if (kind != HidClassType::HID as u8) {
+            return Err(anyhow!("This is not a hid descriptor"));
+        }
+        
+        let num_descriptors = bytes[5];
+
+        if (length != Self::HID_DESC_FIXED_SIZE + num_descriptors * Self::HID_CLASS_DESC_SIZE) {
+            return Err(anyhow!("Len doesn't match the given number of descriptors ({num_descriptors})"));
+        }
+        
+        let mut descriptors = SmallVec::<[HidClassDescriptor; 1]>::with_capacity(num_descriptors as usize);
+        
+        for i in 0..num_descriptors {
+            match HidClassDescriptor::from_bytes(&bytes[(Self::HID_DESC_FIXED_SIZE + i*Self::HID_CLASS_DESC_SIZE) as usize..(Self::HID_DESC_FIXED_SIZE + (i+1)*Self::HID_CLASS_DESC_SIZE) as usize]) {
+                Ok(desc) => descriptors.push(*desc),
+                Err(e) => return Err(anyhow!("{e:?}")),
+            }
+        }
+        
+        Ok(Self {
+            length,
+            kind,
+            hid_spec_release: u16::from_ne_bytes(bytes[2..4].try_into()?),
+            country_code: bytes[4],
+            num_descriptors,
+            descriptors
+        })
+    }
+    
+
+    pub fn get_report_desc(&self) -> Result<HidClassDescriptor> {
+        for desc in self.descriptors.iter() {
+            match desc.desc_type {
+                HidClassType::Report => return Ok(*desc),
+                _ => ()
+            }
+        }
+        return Err(anyhow!("No Report descriptor found"));
+
+    }
+}
\ No newline at end of file
diff --git a/drivers/input/usbhidd/src/main.rs b/drivers/input/usbhidd/src/main.rs
index 15c5b77820..b3cb97e98e 100644
--- a/drivers/input/usbhidd/src/main.rs
+++ b/drivers/input/usbhidd/src/main.rs
@@ -1,4 +1,4 @@
-use anyhow::{Context, Result};
+use anyhow::{anyhow, Context, Result};
 use std::{env, thread, time};
 
 use inputd::ProducerHandle;
@@ -13,7 +13,10 @@ use xhcid_interface::{
     XhciClientHandle,
 };
 
+use crate::descs::HidDescriptor;
+
 mod reqs;
+mod descs;
 
 fn send_key_event(display: &mut ProducerHandle, usage_page: u16, usage: u16, pressed: bool) {
     let scancode = match usage_page {
@@ -217,9 +220,9 @@ fn main() -> Result<()> {
                             None
                         }
                     });
-                    let hid_desc = if_desc.hid_descs.iter().find_map(|hid_desc| {
+                    let hid_desc = if_desc.unknown_descs.iter().find_map(|unknown_desc| {
                         //TODO: should we do any filtering?
-                        Some(hid_desc)
+                        HidDescriptor::from_bytes(&unknown_desc.all_bytes).ok()
                     })?;
                     Some((if_desc.clone(), endp_desc_opt, hid_desc))
                 } else {
@@ -246,8 +249,7 @@ fn main() -> Result<()> {
     // This sets all reports to a duration of 4ms
     reqs::set_idle(&handle, 1, 0, interface_num as u16).context("Failed to set idle")?;
 
-    let report_desc_len = hid_desc.desc_len;
-    assert_eq!(hid_desc.desc_ty, REPORT_DESC_TY);
+    let report_desc_len = hid_desc.get_report_desc()?.desc_len;
 
     let mut report_desc_bytes = vec![0u8; report_desc_len as usize];
     handle