diff --git a/src/fde.rs b/src/fde/custom.rs
similarity index 82%
rename from src/fde.rs
rename to src/fde/custom.rs
index 0f21caf..47f8e72 100644
--- a/src/fde.rs
+++ b/src/fde/custom.rs
@@ -3,261 +3,27 @@
 #![allow(clippy::collapsible_if)]
 #![allow(clippy::collapsible_match)]
 
+use super::*;
+
 use core::{cmp, mem, ptr, slice};
 use orbclient::{Color, Renderer};
 use orbfont::Text;
 use std::ffi;
 use std::prelude::*;
 use std::proto::Protocol;
-use std::uefi::hii::database::HiiHandle;
+use std::uefi::hii::StringId;
 use std::uefi::hii::ifr::{
-    HiiValue, IfrAction, IfrCheckbox, IfrNumeric, IfrOneOf, IfrOneOfOption, IfrOpCode, IfrOpHeader,
-    IfrOrderedList, IfrRef, IfrStatementHeader, IfrSubtitle, IfrTypeValueEnum,
+    IfrAction, IfrCheckbox, IfrNumeric, IfrOneOf, IfrOpCode, IfrOrderedList, IfrRef,
+    IfrStatementHeader, IfrSubtitle, IfrTypeValueEnum,
 };
-use std::uefi::hii::{AnimationId, ImageId, StringId};
-use std::uefi::text::TextInputKey;
 
 use crate::display::{Display, Output};
 use crate::hii::string::HiiStringProtocol;
 use crate::key::{Key, raw_key};
 use crate::ui::Ui;
 
-// TODO: move to uefi library {
-#[repr(C)]
-pub struct ListEntry<T> {
-    Flink: *mut ListEntry<T>,
-    Blink: *mut ListEntry<T>,
-}
-
-#[allow(dead_code)]
-impl<T> ListEntry<T> {
-    pub fn previous(&self) -> Option<&Self> {
-        if self.Blink.is_null() {
-            None
-        } else {
-            Some(unsafe { &*self.Blink })
-        }
-    }
-
-    pub fn previous_mut(&mut self) -> Option<&mut Self> {
-        if self.Blink.is_null() {
-            None
-        } else {
-            Some(unsafe { &mut *self.Blink })
-        }
-    }
-
-    pub fn next(&self) -> Option<&Self> {
-        if self.Flink.is_null() {
-            None
-        } else {
-            Some(unsafe { &*self.Flink })
-        }
-    }
-
-    pub fn next_mut(&mut self) -> Option<&mut Self> {
-        if self.Flink.is_null() {
-            None
-        } else {
-            Some(unsafe { &mut *self.Flink })
-        }
-    }
-
-    unsafe fn object_at(&self, offset: usize) -> &T {
-        let addr = self as *const Self as usize;
-        unsafe { &*((addr - offset) as *const T) }
-    }
-
-    unsafe fn object_at_mut(&mut self, offset: usize) -> &mut T {
-        let addr = self as *mut Self as usize;
-        unsafe { &mut *((addr - offset) as *mut T) }
-    }
-}
-
-pub trait ListEntryObject<T> {
-    unsafe fn object(&self) -> &T;
-
-    #[allow(dead_code)]
-    unsafe fn object_mut(&mut self) -> &mut T;
-}
-
-macro_rules! list_entry {
-    ($t:ident, $l:tt) => {
-        impl ListEntryObject<$t> for ListEntry<$t> {
-            unsafe fn object(&self) -> &$t {
-                unsafe { self.object_at(mem::offset_of!($t, $l)) }
-            }
-
-            unsafe fn object_mut(&mut self) -> &mut $t {
-                unsafe { self.object_at_mut(mem::offset_of!($t, $l)) }
-            }
-        }
-    };
-}
-
-pub struct ListEntryIter<'a, T> {
-    start: Option<&'a ListEntry<T>>,
-    current: Option<&'a ListEntry<T>>,
-}
-
-impl<'a, T> Iterator for ListEntryIter<'a, T>
-where
-    ListEntry<T>: ListEntryObject<T>,
-{
-    type Item = &'a T;
-    fn next(&mut self) -> Option<Self::Item> {
-        let current = self.current.take()?;
-        let next = current.next();
-        if next.map(|x| x as *const _) == self.start.map(|x| x as *const _) {
-            self.current = None;
-            return None;
-        } else {
-            self.current = next;
-        }
-        Some(unsafe { current.object() })
-    }
-}
-
-#[repr(transparent)]
-pub struct ListHead<T>(ListEntry<T>);
-
-impl<T> ListHead<T> {
-    pub fn iter(&self) -> ListEntryIter<'_, T> {
-        let next = self.0.next();
-        ListEntryIter {
-            start: next,
-            current: next,
-        }
-    }
-}
-// } TODO: move to uefi library
-
-#[repr(C)]
-pub struct QuestionOption {
-    pub Signature: usize,
-    pub Link: ListEntry<QuestionOption>,
-    pub OptionOpCodePtr: *const IfrOneOfOption,
-    pub ImageId: ImageId,
-    pub AnimationId: AnimationId,
-}
-list_entry!(QuestionOption, Link);
-
-impl QuestionOption {
-    pub fn OptionOpCode(&self) -> Option<&IfrOneOfOption> {
-        if self.OptionOpCodePtr.is_null() {
-            None
-        } else {
-            Some(unsafe { &*self.OptionOpCodePtr })
-        }
-    }
-}
-
-#[repr(C)]
-pub struct StatementErrorInfo {
-    pub StringId: StringId,
-    pub TimeOut: u8,
-}
-
-pub type ValidateQuestion = extern "efiapi" fn(
-    Form: &Form,
-    Statement: &Statement,
-    Value: &HiiValue,
-    ErrorInfo: &mut StatementErrorInfo,
-) -> u32;
-
-pub type PasswordCheck =
-    extern "efiapi" fn(Form: &Form, Statement: &Statement, PasswordString: *const u16) -> Status;
-
-#[repr(C)]
-pub struct Statement {
-    pub Signature: usize,
-    pub Version: usize,
-    pub DisplayLink: ListEntry<Statement>,
-    pub OpCodePtr: *const IfrOpHeader,
-    pub CurrentValue: HiiValue,
-    pub SettingChangedFlag: bool,
-    pub NestStatementList: ListHead<Statement>,
-    pub OptionListHead: ListHead<QuestionOption>,
-    pub Attribute: u32,
-    pub ValidateQuestion: Option<ValidateQuestion>,
-    pub PasswordCheck: Option<PasswordCheck>,
-    pub ImageId: ImageId,
-    pub AnimationId: AnimationId,
-}
-list_entry!(Statement, DisplayLink);
-
-impl Statement {
-    pub fn OpCode(&self) -> Option<&IfrOpHeader> {
-        if self.OpCodePtr.is_null() {
-            None
-        } else {
-            Some(unsafe { &*self.OpCodePtr })
-        }
-    }
-}
-
-#[repr(C)]
-pub struct ScreenDescriptor {
-    pub LeftColumn: usize,
-    pub RightColumn: usize,
-    pub TopRow: usize,
-    pub BottomRow: usize,
-}
-
-#[repr(C)]
-pub struct HotKey {
-    pub Signature: usize,
-    pub Link: ListEntry<HotKey>,
-    pub KeyData: *const TextInputKey,
-    pub Action: u32,
-    pub DefaultId: u16,
-    pub HelpString: *const u16,
-}
-list_entry!(HotKey, Link);
-
-#[repr(C)]
-pub struct Form {
-    pub Signature: usize,
-    pub Version: usize,
-    pub StatementListHead: ListHead<Statement>,
-    pub StatementListOSF: ListHead<Statement>,
-    pub ScreenDimensions: *const ScreenDescriptor,
-    pub FormSetGuid: Guid,
-    pub HiiHandle: HiiHandle,
-    pub FormId: u16,
-    pub FormTitle: StringId,
-    pub Attribute: u32,
-    pub SettingChangedFlag: bool,
-    pub HighLightedStatement: *const Statement,
-    pub FormRefreshEvent: Event,
-    pub HotKeyListHead: ListHead<HotKey>,
-    pub ImageId: ImageId,
-    pub AnimationId: AnimationId,
-    pub BrowserStatus: u32,
-    pub ErrorString: *const u16,
-}
-
 const FRONT_PAGE_FORM_ID: u16 = 0x7600;
 
-const BROWSER_ACTION_NONE: u32 = 1 << 16;
-const BROWSER_ACTION_FORM_EXIT: u32 = 1 << 17;
-
-#[repr(C)]
-pub struct UserInput {
-    pub SelectedStatement: *const Statement,
-    pub InputValue: HiiValue,
-    pub Action: u32,
-    pub DefaultId: u16,
-}
-
-#[repr(C)]
-#[allow(non_snake_case)]
-pub struct Fde {
-    pub FormDisplay: extern "efiapi" fn(FormData: &Form, UserInputData: &mut UserInput) -> Status,
-    pub ExitDisplay: extern "efiapi" fn(),
-    pub ConfirmDataChange: extern "efiapi" fn() -> usize,
-}
-
 static mut DISPLAY: *mut Display = ptr::null_mut();
 
 #[allow(dead_code)]
@@ -980,8 +746,17 @@ fn form_display_inner(form: &Form, user_input: &mut UserInput) -> Result<()> {
     Ok(())
 }
 
-extern "efiapi" fn form_display(form: &Form, user_input: &mut UserInput) -> Status {
-    form_display_inner(form, user_input).into()
+extern "efiapi" fn form_display(form: *const Form, user_input: *mut UserInput) -> Status {
+    if form.is_null() || user_input.is_null() {
+        return Status::INVALID_PARAMETER;
+    }
+
+    // SAFETY: Pointer is valid.
+    let form = unsafe { &*form };
+    // SAFETY: Pointer is valid.
+    let input = unsafe { &mut *user_input };
+
+    form_display_inner(form, input).into()
 }
 
 extern "efiapi" fn exit_display() {}
@@ -990,22 +765,24 @@ extern "efiapi" fn confirm_data_change() -> usize {
     0
 }
 
-impl Fde {
-    pub fn install() -> Result<()> {
-        let guid = guid!("9bbe29e9-fda1-41ec-ad52-452213742d2e");
-
-        let uefi = unsafe { std::system_table_mut() };
-
-        let current = unsafe {
-            let mut interface = 0;
-            Result::from((uefi.BootServices.LocateProtocol)(&guid, 0, &mut interface))?;
-            &mut *(interface as *mut Fde)
-        };
+// TODO: Implement HII Popup and correctly install the protocols instead of
+// modifying the function pointers of the edk2 installed protocol.
+pub fn install() -> Result<()> {
+    let uefi = unsafe { std::system_table_mut() };
+
+    let current = unsafe {
+        let mut interface = 0;
+        Result::from((uefi.BootServices.LocateProtocol)(
+            &FormDisplayEngine::GUID,
+            0,
+            &mut interface,
+        ))?;
+        &mut *(interface as *mut FormDisplayEngine)
+    };
 
-        current.FormDisplay = form_display;
-        current.ExitDisplay = exit_display;
-        current.ConfirmDataChange = confirm_data_change;
+    current.FormDisplay = form_display;
+    current.ExitDisplay = exit_display;
+    current.ConfirmDataChange = confirm_data_change;
 
-        Ok(())
-    }
+    Ok(())
 }
diff --git a/src/fde/list.rs b/src/fde/list.rs
new file mode 100644
index 0000000..03807dd
--- /dev/null
+++ b/src/fde/list.rs
@@ -0,0 +1,112 @@
+// SPDX-License-Identifier: GPL-3.0-only
+
+// `LIST_ENTRY` implemenation
+// TODO: Move to uefi library
+
+#[repr(C)]
+pub struct ListEntry<T> {
+    pub Flink: *mut ListEntry<T>,
+    pub Blink: *mut ListEntry<T>,
+}
+
+#[allow(dead_code)]
+impl<T> ListEntry<T> {
+    pub fn previous(&self) -> Option<&Self> {
+        if self.Blink.is_null() {
+            None
+        } else {
+            Some(unsafe { &*self.Blink })
+        }
+    }
+
+    pub fn previous_mut(&mut self) -> Option<&mut Self> {
+        if self.Blink.is_null() {
+            None
+        } else {
+            Some(unsafe { &mut *self.Blink })
+        }
+    }
+
+    pub fn next(&self) -> Option<&Self> {
+        if self.Flink.is_null() {
+            None
+        } else {
+            Some(unsafe { &*self.Flink })
+        }
+    }
+
+    pub fn next_mut(&mut self) -> Option<&mut Self> {
+        if self.Flink.is_null() {
+            None
+        } else {
+            Some(unsafe { &mut *self.Flink })
+        }
+    }
+
+    pub unsafe fn object_at(&self, offset: usize) -> &T {
+        let addr = self as *const Self as usize;
+        unsafe { &*((addr - offset) as *const T) }
+    }
+
+    pub unsafe fn object_at_mut(&mut self, offset: usize) -> &mut T {
+        let addr = self as *mut Self as usize;
+        unsafe { &mut *((addr - offset) as *mut T) }
+    }
+}
+
+pub trait ListEntryObject<T> {
+    unsafe fn object(&self) -> &T;
+
+    #[allow(dead_code)]
+    unsafe fn object_mut(&mut self) -> &mut T;
+}
+
+macro_rules! list_entry {
+    ($t:ident, $l:tt) => {
+        impl ListEntryObject<$t> for ListEntry<$t> {
+            unsafe fn object(&self) -> &$t {
+                unsafe { self.object_at(core::mem::offset_of!($t, $l)) }
+            }
+
+            unsafe fn object_mut(&mut self) -> &mut $t {
+                unsafe { self.object_at_mut(core::mem::offset_of!($t, $l)) }
+            }
+        }
+    };
+}
+
+pub struct ListEntryIter<'a, T> {
+    start: Option<&'a ListEntry<T>>,
+    current: Option<&'a ListEntry<T>>,
+}
+
+impl<'a, T> Iterator for ListEntryIter<'a, T>
+where
+    ListEntry<T>: ListEntryObject<T>,
+{
+    type Item = &'a T;
+    fn next(&mut self) -> Option<Self::Item> {
+        let current = self.current.take()?;
+        let next = current.next();
+        if next.map(|x| x as *const _) == self.start.map(|x| x as *const _) {
+            self.current = None;
+            return None;
+        } else {
+            self.current = next;
+        }
+        Some(unsafe { current.object() })
+    }
+}
+
+#[repr(transparent)]
+pub struct ListHead<T>(ListEntry<T>);
+
+impl<T> ListHead<T> {
+    pub fn iter(&self) -> ListEntryIter<'_, T> {
+        let next = self.0.next();
+        ListEntryIter {
+            start: next,
+            current: next,
+        }
+    }
+}
diff --git a/src/fde/mod.rs b/src/fde/mod.rs
new file mode 100644
index 0000000..9c41773
--- /dev/null
+++ b/src/fde/mod.rs
@@ -0,0 +1,171 @@
+// SPDX-License-Identifier: GPL-3.0-only
+
+//! edk2 Form Display Engine (FDE) Protocol
+
+pub mod custom;
+#[macro_use]
+pub mod list;
+
+use list::*;
+use std::prelude::*;
+use std::uefi::hii::database::HiiHandle;
+use std::uefi::hii::ifr::{HiiValue, IfrOneOfOption, IfrOpHeader};
+use std::uefi::hii::{AnimationId, ImageId, StringId};
+use std::uefi::text::TextInputKey;
+
+// TODO: Move to FormBrowser2
+#[repr(C)]
+pub struct ScreenDescriptor {
+    pub LeftColumn: usize,
+    pub RightColumn: usize,
+    pub TopRow: usize,
+    pub BottomRow: usize,
+}
+
+// Custom browser actions defined by FDE.
+pub const BROWSER_ACTION_NONE: u32 = 1 << 16;
+pub const BROWSER_ACTION_FORM_EXIT: u32 = 1 << 17;
+
+/// `DISPLAY_QUESTION_OPTION`
+#[repr(C)]
+pub struct QuestionOption {
+    pub Signature: usize,
+    pub Link: ListEntry<QuestionOption>,
+    pub OptionOpCodePtr: *const IfrOneOfOption,
+    pub ImageId: ImageId,
+    pub AnimationId: AnimationId,
+}
+list_entry!(QuestionOption, Link);
+
+#[allow(dead_code)]
+impl QuestionOption {
+    pub const SIGNATURE: u32 = u32::from_le_bytes(*b"QOPT");
+
+    pub fn OptionOpCode(&self) -> Option<&IfrOneOfOption> {
+        if self.OptionOpCodePtr.is_null() {
+            None
+        } else {
+            Some(unsafe { &*self.OptionOpCodePtr })
+        }
+    }
+}
+
+/// `STATEMENT_ERROR_INFO`
+#[repr(C)]
+pub struct StatementErrorInfo {
+    pub StringId: StringId,
+    pub TimeOut: u8,
+}
+
+/// `FORM_DISPLAY_ENGINE_STATEMENT`
+#[repr(C)]
+pub struct Statement {
+    pub Signature: usize,
+    pub Version: usize,
+    pub DisplayLink: ListEntry<Statement>,
+    pub OpCodePtr: *const IfrOpHeader,
+    pub CurrentValue: HiiValue,
+    pub SettingChangedFlag: bool,
+    pub NestStatementList: ListHead<Statement>,
+    pub OptionListHead: ListHead<QuestionOption>,
+    pub Attribute: u32,
+    pub ValidateQuestion: unsafe extern "efiapi" fn(
+        form: *const Form,
+        statement: *const Self,
+        value: *const HiiValue,
+        error_info: *mut StatementErrorInfo,
+    ) -> u32,
+    pub PasswordCheck: unsafe extern "efiapi" fn(
+        form: *const Form,
+        statement: *const Self,
+        password_string: *const u16,
+    ) -> Status,
+    pub ImageId: ImageId,
+    pub AnimationId: AnimationId,
+}
+list_entry!(Statement, DisplayLink);
+
+#[allow(dead_code)]
+impl Statement {
+    pub const SIGNATURE: u32 = u32::from_le_bytes(*b"FSTA");
+    pub const VERSION_1: usize = 0x1_0000;
+
+    pub fn OpCode(&self) -> Option<&IfrOpHeader> {
+        if self.OpCodePtr.is_null() {
+            None
+        } else {
+            Some(unsafe { &*self.OpCodePtr })
+        }
+    }
+}
+
+/// `BROWSER_HOT_KEY`
+#[repr(C)]
+pub struct HotKey {
+    pub Signature: usize,
+    pub Link: ListEntry<HotKey>,
+    pub KeyData: *const TextInputKey,
+    pub Action: u32,
+    pub DefaultId: u16,
+    pub HelpString: *const u16,
+}
+list_entry!(HotKey, Link);
+
+#[allow(dead_code)]
+impl HotKey {
+    pub const SIGNATURE: u32 = u32::from_le_bytes(*b"BHKS");
+}
+
+/// `FORM_DISPLAY_ENGINE_FORM`
+#[repr(C)]
+pub struct Form {
+    pub Signature: usize,
+    pub Version: usize,
+    pub StatementListHead: ListHead<Statement>,
+    pub StatementListOSF: ListHead<Statement>,
+    pub ScreenDimensions: *const ScreenDescriptor,
+    pub FormSetGuid: Guid,
+    pub HiiHandle: HiiHandle,
+    pub FormId: u16,
+    pub FormTitle: StringId,
+    pub Attribute: u32,
+    pub SettingChangedFlag: bool,
+    pub HighLightedStatement: *const Statement,
+    pub FormRefreshEvent: Event,
+    pub HotKeyListHead: ListHead<HotKey>,
+    pub ImageId: ImageId,
+    pub AnimationId: AnimationId,
+    pub BrowserStatus: u32,
+    pub ErrorString: *const u16,
+}
+
+#[allow(dead_code)]
+impl Form {
+    pub const SIGNATURE: u32 = u32::from_le_bytes(*b"FFRM");
+    pub const VERSION_1: usize = 0x1_0000;
+}
+
+/// `USER_INPUT`
+#[repr(C)]
+pub struct UserInput {
+    pub SelectedStatement: *const Statement,
+    pub InputValue: HiiValue,
+    pub Action: u32,
+    pub DefaultId: u16,
+}
+
+/// `EDKII_FORM_DISPLAY_ENGINE_PROTOCOL`
+#[derive(Debug)]
+#[repr(C)]
+pub struct FormDisplayEngine {
+    pub FormDisplay: unsafe extern "efiapi" fn(
+        form_data: *const Form,
+        user_input_data: *mut UserInput,
+    ) -> Status,
+    pub ExitDisplay: unsafe extern "efiapi" fn(),
+    pub ConfirmDataChange: unsafe extern "efiapi" fn() -> usize,
+}
+
+impl FormDisplayEngine {
+    pub const GUID: Guid = guid!("9bbe29e9-fda1-41ec-ad52-452213742d2e");
+}
diff --git a/src/main.rs b/src/main.rs
index 14778c3..ef57847 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -26,8 +26,8 @@ pub extern "C" fn main() -> Status {
 
     let _ = (uefi.BootServices.SetWatchdogTimer)(0, 0, 0, ptr::null());
 
-    if let Err(err) = fde::Fde::install() {
-        println!("Fde error: {:?}", err);
+    if let Err(err) = fde::custom::install() {
+        println!("FDE error: {:?}", err);
         let _ = key::key(true);
     }
 
@@ -36,5 +36,5 @@ pub extern "C" fn main() -> Status {
         let _ = key::key(true);
     }
 
-    Status(0)
+    Status::SUCCESS
 }