From 25b03414dc83a7b117e8acde28a81f79d5de20c9 Mon Sep 17 00:00:00 2001
From: deadprogram <ron@hybridgroup.com>
Date: Mon, 17 Apr 2023 14:38:15 +0200
Subject: [PATCH] machine/usb/hid/joystick: handle case where we cannot find
 the correct HID descriptor

Signed-off-by: deadprogram <ron@hybridgroup.com>
---
 src/machine/usb.go                       |  7 ++++++-
 src/machine/usb/descriptor/hid.go        | 19 ++++++++++++++++---
 src/machine/usb/hid/joystick/joystick.go |  2 +-
 3 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/src/machine/usb.go b/src/machine/usb.go
index 7a72e164..a90fab17 100644
--- a/src/machine/usb.go
+++ b/src/machine/usb.go
@@ -302,7 +302,12 @@ func EnableMIDI(txHandler func(), rxHandler func([]byte), setupHandler func(usb.
 
 // EnableJoystick enables HID. This function must be executed from the init().
 func EnableJoystick(txHandler func(), rxHandler func([]byte), setupHandler func(usb.Setup) bool, hidDesc []byte) {
-	class := descriptor.FindClassHIDType(descriptor.CDCJoystick.Configuration, descriptor.ClassHIDJoystick.Bytes())
+	class, err := descriptor.FindClassHIDType(descriptor.CDCJoystick.Configuration, descriptor.ClassHIDJoystick.Bytes())
+	if err != nil {
+		// TODO: some way to notify about error
+		return
+	}
+
 	class.ClassLength(uint16(len(hidDesc)))
 	descriptor.CDCJoystick.HID[2] = hidDesc
 
diff --git a/src/machine/usb/descriptor/hid.go b/src/machine/usb/descriptor/hid.go
index 266d1006..925bb78d 100644
--- a/src/machine/usb/descriptor/hid.go
+++ b/src/machine/usb/descriptor/hid.go
@@ -3,6 +3,7 @@ package descriptor
 import (
 	"bytes"
 	"encoding/binary"
+	"errors"
 )
 
 var configurationCDCHID = [configurationTypeLen]byte{
@@ -76,10 +77,22 @@ func (d ClassHIDType) ClassLength(v uint16) {
 	binary.LittleEndian.PutUint16(d.data[7:9], v)
 }
 
-func FindClassHIDType(data, section []byte) ClassHIDType {
-	idx := bytes.Index(data, section)
+var errNoClassHIDFound = errors.New("no classHID found")
 
-	return ClassHIDType{data: data[idx : idx+ClassHIDTypeLen]}
+// FindClassHIDType tries to find the ClassHID class in the descriptor.
+func FindClassHIDType(des, class []byte) (ClassHIDType, error) {
+	if len(des) < ClassHIDTypeLen || len(class) == 0 {
+		return ClassHIDType{}, errNoClassHIDFound
+	}
+
+	// search only for ClassHIDType without the ClassLength,
+	// in case it has already been set.
+	idx := bytes.Index(des, class[:ClassHIDTypeLen-2])
+	if idx == -1 {
+		return ClassHIDType{}, errNoClassHIDFound
+	}
+
+	return ClassHIDType{data: des[idx : idx+ClassHIDTypeLen]}, nil
 }
 
 var classHID = [ClassHIDTypeLen]byte{
diff --git a/src/machine/usb/hid/joystick/joystick.go b/src/machine/usb/hid/joystick/joystick.go
index cdcf771d..763b39ee 100644
--- a/src/machine/usb/hid/joystick/joystick.go
+++ b/src/machine/usb/hid/joystick/joystick.go
@@ -30,7 +30,7 @@ func UseSettings(def Definitions, rxHandlerFunc func(b []byte), setupFunc func(s
 		State: def.NewState(),
 	}
 	if setupFunc == nil {
-		setupFunc = js.setupFunc
+		setupFunc = hid.DefaultSetupHandler
 	}
 	machine.EnableJoystick(js.handler, rxHandlerFunc, setupFunc, hidDesc)
 	Joystick = js