Merge changes I54ee0330,I26e77cc1,Ib9515431 into main

* changes:
  libfdt: Replace helper functions with FdtRawResult
  libfdt: Introduce FdtRawResult abstraction type
  libfdt: Move pack(), unpack(), apply_overlay()
diff --git a/libs/libfdt/src/ctypes.rs b/libs/libfdt/src/ctypes.rs
index 640d447..a65f8e7 100644
--- a/libs/libfdt/src/ctypes.rs
+++ b/libs/libfdt/src/ctypes.rs
@@ -14,6 +14,7 @@
 
 //! Safe zero-cost wrappers around integer values used by libfdt.
 
+use crate::result::FdtRawResult;
 use crate::{FdtError, Result};
 
 /// Wrapper guaranteed to contain a valid phandle.
@@ -50,3 +51,11 @@
         Self::new(value).ok_or(FdtError::BadPhandle)
     }
 }
+
+impl TryFrom<FdtRawResult> for Phandle {
+    type Error = FdtError;
+
+    fn try_from(res: FdtRawResult) -> Result<Self> {
+        Self::new(res.try_into()?).ok_or(FdtError::BadPhandle)
+    }
+}
diff --git a/libs/libfdt/src/lib.rs b/libs/libfdt/src/lib.rs
index d254af1..a34ecbb 100644
--- a/libs/libfdt/src/lib.rs
+++ b/libs/libfdt/src/lib.rs
@@ -33,7 +33,6 @@
 use core::ops::Range;
 use cstr::cstr;
 use libfdt::get_slice_at_ptr;
-use result::{fdt_err, fdt_err_expect_zero, fdt_err_or_option};
 use zerocopy::AsBytes as _;
 
 use crate::libfdt::{Libfdt, LibfdtMut};
@@ -637,40 +636,30 @@
 
     /// Unpacks the DT to cover the whole slice it is contained in.
     pub fn unpack(&mut self) -> Result<()> {
-        // SAFETY: "Opens" the DT in-place (supported use-case) by updating its header and
-        // internal structures to make use of the whole self.fdt slice but performs no accesses
-        // outside of it and leaves the DT in a state that will be detected by other functions.
-        let ret = unsafe {
-            libfdt_bindgen::fdt_open_into(
-                self.as_ptr(),
-                self.as_mut_ptr(),
-                self.capacity().try_into().map_err(|_| FdtError::Internal)?,
-            )
-        };
-        fdt_err_expect_zero(ret)
+        self.open_into_self()
     }
 
     /// Packs the DT to take a minimum amount of memory.
     ///
     /// Doesn't shrink the underlying memory slice.
     pub fn pack(&mut self) -> Result<()> {
-        // SAFETY: "Closes" the DT in-place by updating its header and relocating its structs.
-        let ret = unsafe { libfdt_bindgen::fdt_pack(self.as_mut_ptr()) };
-        fdt_err_expect_zero(ret)
+        LibfdtMut::pack(self)
     }
 
     /// Applies a DT overlay on the base DT.
     ///
     /// # Safety
     ///
-    /// On failure, the library corrupts the DT and overlay so both must be discarded.
-    pub unsafe fn apply_overlay<'a>(&'a mut self, overlay: &'a mut Fdt) -> Result<&'a mut Self> {
-        let ret =
-        // SAFETY: Both pointers are valid because they come from references, and fdt_overlay_apply
-        // doesn't keep them after it returns. It may corrupt their contents if there is an error,
-        // but that's our caller's responsibility.
-            unsafe { libfdt_bindgen::fdt_overlay_apply(self.as_mut_ptr(), overlay.as_mut_ptr()) };
-        fdt_err_expect_zero(ret)?;
+    /// As libfdt corrupts the input DT on failure, `self` should be discarded on error:
+    ///
+    ///     let fdt = fdt.apply_overlay(overlay)?;
+    ///
+    /// Furthermore, `overlay` is _always_ corrupted by libfdt and will never refer to a valid
+    /// `Fdt` after this function returns and must therefore be discarded by the caller.
+    pub unsafe fn apply_overlay<'a>(&'a mut self, overlay: &mut Fdt) -> Result<&'a mut Self> {
+        // SAFETY: Our caller will properly discard overlay and/or self as needed.
+        unsafe { self.overlay_apply(overlay) }?;
+
         Ok(self)
     }
 
@@ -785,14 +774,6 @@
         self.buffer.as_ptr().cast()
     }
 
-    fn as_mut_ptr(&mut self) -> *mut c_void {
-        self.buffer.as_mut_ptr().cast::<_>()
-    }
-
-    fn capacity(&self) -> usize {
-        self.buffer.len()
-    }
-
     fn header(&self) -> &libfdt_bindgen::fdt_header {
         let p = self.as_ptr().cast();
         // SAFETY: A valid FDT (verified by constructor) must contain a valid fdt_header.
diff --git a/libs/libfdt/src/libfdt.rs b/libs/libfdt/src/libfdt.rs
index 7737718..1e82c9f 100644
--- a/libs/libfdt/src/libfdt.rs
+++ b/libs/libfdt/src/libfdt.rs
@@ -22,7 +22,8 @@
 use core::mem;
 use core::ptr;
 
-use crate::{fdt_err, fdt_err_expect_zero, fdt_err_or_option, FdtError, Phandle, Result};
+use crate::result::FdtRawResult;
+use crate::{FdtError, Phandle, Result};
 
 // Function names are the C function names without the `fdt_` prefix.
 
@@ -35,7 +36,7 @@
     //          There will be no memory write outside of the given fdt.
     let ret = unsafe { libfdt_bindgen::fdt_create_empty_tree(fdt, len) };
 
-    fdt_err_expect_zero(ret)
+    FdtRawResult::from(ret).try_into()
 }
 
 /// Safe wrapper around `fdt_check_full()` (C function).
@@ -49,7 +50,7 @@
     // calls as it expects the client code to keep track of the objects (DT, nodes, ...).
     let ret = unsafe { libfdt_bindgen::fdt_check_full(fdt, len) };
 
-    fdt_err_expect_zero(ret)
+    FdtRawResult::from(ret).try_into()
 }
 
 /// Wrapper for the read-only libfdt.h functions.
@@ -76,7 +77,7 @@
         // function respects the passed number of characters.
         let ret = unsafe { libfdt_bindgen::fdt_path_offset_namelen(fdt, path, len) };
 
-        fdt_err_or_option(ret)
+        FdtRawResult::from(ret).try_into()
     }
 
     /// Safe wrapper around `fdt_node_offset_by_phandle()` (C function).
@@ -86,7 +87,7 @@
         // SAFETY: Accesses are constrained to the DT totalsize.
         let ret = unsafe { libfdt_bindgen::fdt_node_offset_by_phandle(fdt, phandle) };
 
-        fdt_err_or_option(ret)
+        FdtRawResult::from(ret).try_into()
     }
 
     /// Safe wrapper around `fdt_node_offset_by_compatible()` (C function).
@@ -96,7 +97,7 @@
         // SAFETY: Accesses (read-only) are constrained to the DT totalsize.
         let ret = unsafe { libfdt_bindgen::fdt_node_offset_by_compatible(fdt, prev, compatible) };
 
-        fdt_err_or_option(ret)
+        FdtRawResult::from(ret).try_into()
     }
 
     /// Safe wrapper around `fdt_next_node()` (C function).
@@ -106,7 +107,7 @@
         // SAFETY: Accesses (read-only) are constrained to the DT totalsize.
         let ret = unsafe { libfdt_bindgen::fdt_next_node(fdt, node, &mut depth) };
 
-        match fdt_err_or_option(ret)? {
+        match FdtRawResult::from(ret).try_into()? {
             Some(offset) if depth >= 0 => {
                 let depth = depth.try_into().unwrap();
                 Ok(Some((offset, depth)))
@@ -123,7 +124,7 @@
         // SAFETY: Accesses (read-only) are constrained to the DT totalsize.
         let ret = unsafe { libfdt_bindgen::fdt_parent_offset(fdt, node) };
 
-        fdt_err(ret)
+        FdtRawResult::from(ret).try_into()
     }
 
     /// Safe wrapper around `fdt_supernode_atdepth_offset()` (C function).
@@ -138,7 +139,7 @@
             // SAFETY: Accesses (read-only) are constrained to the DT totalsize.
             unsafe { libfdt_bindgen::fdt_supernode_atdepth_offset(fdt, node, depth, nodedepth) };
 
-        fdt_err(ret)
+        FdtRawResult::from(ret).try_into()
     }
 
     /// Safe wrapper around `fdt_subnode_offset_namelen()` (C function).
@@ -149,7 +150,7 @@
         // SAFETY: Accesses are constrained to the DT totalsize (validated by ctor).
         let ret = unsafe { libfdt_bindgen::fdt_subnode_offset_namelen(fdt, parent, name, namelen) };
 
-        fdt_err_or_option(ret)
+        FdtRawResult::from(ret).try_into()
     }
     /// Safe wrapper around `fdt_first_subnode()` (C function).
     fn first_subnode(&self, node: c_int) -> Result<Option<c_int>> {
@@ -157,7 +158,7 @@
         // SAFETY: Accesses (read-only) are constrained to the DT totalsize.
         let ret = unsafe { libfdt_bindgen::fdt_first_subnode(fdt, node) };
 
-        fdt_err_or_option(ret)
+        FdtRawResult::from(ret).try_into()
     }
 
     /// Safe wrapper around `fdt_next_subnode()` (C function).
@@ -166,7 +167,7 @@
         // SAFETY: Accesses (read-only) are constrained to the DT totalsize.
         let ret = unsafe { libfdt_bindgen::fdt_next_subnode(fdt, node) };
 
-        fdt_err_or_option(ret)
+        FdtRawResult::from(ret).try_into()
     }
 
     /// Safe wrapper around `fdt_address_cells()` (C function).
@@ -175,7 +176,7 @@
         // SAFETY: Accesses are constrained to the DT totalsize (validated by ctor).
         let ret = unsafe { libfdt_bindgen::fdt_address_cells(fdt, node) };
 
-        Ok(fdt_err(ret)?.try_into().unwrap())
+        FdtRawResult::from(ret).try_into()
     }
 
     /// Safe wrapper around `fdt_size_cells()` (C function).
@@ -184,7 +185,7 @@
         // SAFETY: Accesses are constrained to the DT totalsize (validated by ctor).
         let ret = unsafe { libfdt_bindgen::fdt_size_cells(fdt, node) };
 
-        Ok(fdt_err(ret)?.try_into().unwrap())
+        FdtRawResult::from(ret).try_into()
     }
 
     /// Safe wrapper around `fdt_get_name()` (C function).
@@ -194,7 +195,7 @@
         // SAFETY: Accesses are constrained to the DT totalsize (validated by ctor). On success, the
         // function returns valid null terminating string and otherwise returned values are dropped.
         let name = unsafe { libfdt_bindgen::fdt_get_name(fdt, node, &mut len) };
-        let len = usize::try_from(fdt_err(len)?).unwrap().checked_add(1).unwrap();
+        let len = usize::try_from(FdtRawResult::from(len))?.checked_add(1).unwrap();
 
         get_slice_at_ptr(self.as_fdt_slice(), name.cast(), len).ok_or(FdtError::Internal)
     }
@@ -210,8 +211,7 @@
             // function respects the passed number of characters.
             unsafe { libfdt_bindgen::fdt_getprop_namelen(fdt, node, name, namelen, &mut len) };
 
-        if let Some(len) = fdt_err_or_option(len)? {
-            let len = usize::try_from(len).unwrap();
+        if let Some(len) = FdtRawResult::from(len).try_into()? {
             let bytes = get_slice_at_ptr(self.as_fdt_slice(), prop.cast(), len);
 
             Ok(Some(bytes.ok_or(FdtError::Internal)?))
@@ -227,7 +227,7 @@
         // SAFETY: Accesses (read-only) are constrained to the DT totalsize.
         let prop = unsafe { libfdt_bindgen::fdt_get_property_by_offset(fdt, offset, &mut len) };
 
-        let data_len = fdt_err(len)?.try_into().unwrap();
+        let data_len = FdtRawResult::from(len).try_into()?;
         // TODO(stable_feature(offset_of)): mem::offset_of!(fdt_property, data).
         let data_offset = memoffset::offset_of!(libfdt_bindgen::fdt_property, data);
         let len = data_offset.checked_add(data_len).ok_or(FdtError::Internal)?;
@@ -252,7 +252,7 @@
         // SAFETY: Accesses (read-only) are constrained to the DT totalsize.
         let ret = unsafe { libfdt_bindgen::fdt_first_property_offset(fdt, node) };
 
-        fdt_err_or_option(ret)
+        FdtRawResult::from(ret).try_into()
     }
 
     /// Safe wrapper around `fdt_next_property_offset()` (C function).
@@ -261,7 +261,7 @@
         // SAFETY: Accesses (read-only) are constrained to the DT totalsize.
         let ret = unsafe { libfdt_bindgen::fdt_next_property_offset(fdt, prev) };
 
-        fdt_err_or_option(ret)
+        FdtRawResult::from(ret).try_into()
     }
 
     /// Safe wrapper around `fdt_find_max_phandle()` (C function).
@@ -271,7 +271,7 @@
         // SAFETY: Accesses (read-only) are constrained to the DT totalsize.
         let ret = unsafe { libfdt_bindgen::fdt_find_max_phandle(fdt, &mut phandle) };
 
-        fdt_err_expect_zero(ret)?;
+        FdtRawResult::from(ret).try_into()?;
 
         phandle.try_into()
     }
@@ -286,6 +286,13 @@
 
         CStr::from_bytes_until_nul(bytes).map_err(|_| FdtError::Internal)
     }
+
+    /// Safe wrapper around `fdt_open_into()` (C function).
+    fn open_into(&self, dest: &mut [u8]) -> Result<()> {
+        let fdt = self.as_fdt_slice().as_ptr().cast();
+
+        open_into(fdt, dest)
+    }
 }
 
 /// Wrapper for the read-write libfdt.h functions.
@@ -314,7 +321,7 @@
         // SAFETY: Accesses are constrained to the DT totalsize (validated by ctor).
         let ret = unsafe { libfdt_bindgen::fdt_nop_node(fdt, node) };
 
-        fdt_err_expect_zero(ret)
+        FdtRawResult::from(ret).try_into()
     }
 
     /// Safe wrapper around `fdt_add_subnode_namelen()` (C function).
@@ -325,7 +332,7 @@
         // SAFETY: Accesses are constrained to the DT totalsize (validated by ctor).
         let ret = unsafe { libfdt_bindgen::fdt_add_subnode_namelen(fdt, node, name, namelen) };
 
-        fdt_err(ret)
+        FdtRawResult::from(ret).try_into()
     }
 
     /// Safe wrapper around `fdt_setprop()` (C function).
@@ -338,7 +345,7 @@
         //          (validated by underlying libfdt).
         let ret = unsafe { libfdt_bindgen::fdt_setprop(fdt, node, name, value, len) };
 
-        fdt_err_expect_zero(ret)
+        FdtRawResult::from(ret).try_into()
     }
 
     /// Safe wrapper around `fdt_setprop_placeholder()` (C function).
@@ -351,7 +358,7 @@
             // SAFETY: Accesses are constrained to the DT totalsize (validated by ctor).
             unsafe { libfdt_bindgen::fdt_setprop_placeholder(fdt, node, name, len, &mut data) };
 
-        fdt_err_expect_zero(ret)?;
+        FdtRawResult::from(ret).try_into()?;
 
         get_mut_slice_at_ptr(self.as_fdt_slice_mut(), data.cast(), size).ok_or(FdtError::Internal)
     }
@@ -366,7 +373,7 @@
         //          (validated by underlying libfdt).
         let ret = unsafe { libfdt_bindgen::fdt_setprop_inplace(fdt, node, name, value, len) };
 
-        fdt_err_expect_zero(ret)
+        FdtRawResult::from(ret).try_into()
     }
 
     /// Safe wrapper around `fdt_appendprop()` (C function).
@@ -378,7 +385,7 @@
         // SAFETY: Accesses are constrained to the DT totalsize (validated by ctor).
         let ret = unsafe { libfdt_bindgen::fdt_appendprop(fdt, node, name, value, len) };
 
-        fdt_err_expect_zero(ret)
+        FdtRawResult::from(ret).try_into()
     }
 
     /// Safe wrapper around `fdt_appendprop_addrrange()` (C function).
@@ -397,7 +404,7 @@
             libfdt_bindgen::fdt_appendprop_addrrange(fdt, parent, node, name, addr, size)
         };
 
-        fdt_err_expect_zero(ret)
+        FdtRawResult::from(ret).try_into()
     }
 
     /// Safe wrapper around `fdt_delprop()` (C function).
@@ -410,7 +417,7 @@
         // being called when FdtNode instances are in use.
         let ret = unsafe { libfdt_bindgen::fdt_delprop(fdt, node, name) };
 
-        fdt_err_expect_zero(ret)
+        FdtRawResult::from(ret).try_into()
     }
 
     /// Safe wrapper around `fdt_nop_property()` (C function).
@@ -421,7 +428,49 @@
         // library locates the node's property.
         let ret = unsafe { libfdt_bindgen::fdt_nop_property(fdt, node, name) };
 
-        fdt_err_expect_zero(ret)
+        FdtRawResult::from(ret).try_into()
+    }
+
+    /// Safe and aliasing-compatible wrapper around `fdt_open_into()` (C function).
+    ///
+    /// The C API allows both input (`const void*`) and output (`void *`) to point to the same
+    /// memory region but the borrow checker would reject an API such as
+    ///
+    ///     self.open_into(&mut self.buffer)
+    ///
+    /// so this wrapper is provided to implement such a common aliasing case.
+    fn open_into_self(&mut self) -> Result<()> {
+        let fdt = self.as_fdt_slice_mut();
+
+        open_into(fdt.as_ptr().cast(), fdt)
+    }
+
+    /// Safe wrapper around `fdt_pack()` (C function).
+    fn pack(&mut self) -> Result<()> {
+        let fdt = self.as_fdt_slice_mut().as_mut_ptr().cast();
+        // SAFETY: Accesses (R/W) are constrained to the DT totalsize (validated by ctor).
+        let ret = unsafe { libfdt_bindgen::fdt_pack(fdt) };
+
+        FdtRawResult::from(ret).try_into()
+    }
+
+    /// Wrapper around `fdt_overlay_apply()` (C function).
+    ///
+    /// # Safety
+    ///
+    /// This function safely wraps the C function call but is unsafe because the caller must
+    ///
+    /// - discard `overlay` as a &LibfdtMut because libfdt corrupts its header before returning;
+    /// - on error, discard `self` as a &LibfdtMut for the same reason.
+    unsafe fn overlay_apply(&mut self, overlay: &mut Self) -> Result<()> {
+        let fdt = self.as_fdt_slice_mut().as_mut_ptr().cast();
+        let overlay = overlay.as_fdt_slice_mut().as_mut_ptr().cast();
+        // SAFETY: Both pointers are valid because they come from references, and fdt_overlay_apply
+        // doesn't keep them after it returns. It may corrupt their contents if there is an error,
+        // but that's our caller's responsibility.
+        let ret = unsafe { libfdt_bindgen::fdt_overlay_apply(fdt, overlay) };
+
+        FdtRawResult::from(ret).try_into()
     }
 }
 
@@ -449,6 +498,19 @@
     })
 }
 
+fn open_into(fdt: *const u8, dest: &mut [u8]) -> Result<()> {
+    let fdt = fdt.cast();
+    let len = dest.len().try_into().map_err(|_| FdtError::Internal)?;
+    let dest = dest.as_mut_ptr().cast();
+    // SAFETY: Reads the whole fdt slice (based on the validated totalsize) and, if it fits, copies
+    // it to the (properly mutable) dest buffer of size len. On success, the resulting dest
+    // contains a valid DT with the nodes and properties of the original one but of a different
+    // size, reflected in its fdt_header::totalsize.
+    let ret = unsafe { libfdt_bindgen::fdt_open_into(fdt, dest, len) };
+
+    FdtRawResult::from(ret).try_into()
+}
+
 // TODO(stable_feature(pointer_is_aligned)): p.is_aligned()
 fn is_aligned<T>(p: *const T) -> bool {
     (p as usize) % mem::align_of::<T>() == 0
diff --git a/libs/libfdt/src/result.rs b/libs/libfdt/src/result.rs
index 9643e1e..52291ca 100644
--- a/libs/libfdt/src/result.rs
+++ b/libs/libfdt/src/result.rs
@@ -14,7 +14,7 @@
 
 //! Rust types related to the libfdt C integer results.
 
-use core::ffi::c_int;
+use core::ffi::{c_int, c_uint};
 use core::fmt;
 use core::result;
 
@@ -94,46 +94,99 @@
 /// Result type with FdtError enum.
 pub type Result<T> = result::Result<T, FdtError>;
 
-pub(crate) fn fdt_err(val: c_int) -> Result<c_int> {
-    if val >= 0 {
-        Ok(val)
-    } else {
-        Err(match -val as _ {
-            libfdt_bindgen::FDT_ERR_NOTFOUND => FdtError::NotFound,
-            libfdt_bindgen::FDT_ERR_EXISTS => FdtError::Exists,
-            libfdt_bindgen::FDT_ERR_NOSPACE => FdtError::NoSpace,
-            libfdt_bindgen::FDT_ERR_BADOFFSET => FdtError::BadOffset,
-            libfdt_bindgen::FDT_ERR_BADPATH => FdtError::BadPath,
-            libfdt_bindgen::FDT_ERR_BADPHANDLE => FdtError::BadPhandle,
-            libfdt_bindgen::FDT_ERR_BADSTATE => FdtError::BadState,
-            libfdt_bindgen::FDT_ERR_TRUNCATED => FdtError::Truncated,
-            libfdt_bindgen::FDT_ERR_BADMAGIC => FdtError::BadMagic,
-            libfdt_bindgen::FDT_ERR_BADVERSION => FdtError::BadVersion,
-            libfdt_bindgen::FDT_ERR_BADSTRUCTURE => FdtError::BadStructure,
-            libfdt_bindgen::FDT_ERR_BADLAYOUT => FdtError::BadLayout,
-            libfdt_bindgen::FDT_ERR_INTERNAL => FdtError::Internal,
-            libfdt_bindgen::FDT_ERR_BADNCELLS => FdtError::BadNCells,
-            libfdt_bindgen::FDT_ERR_BADVALUE => FdtError::BadValue,
-            libfdt_bindgen::FDT_ERR_BADOVERLAY => FdtError::BadOverlay,
-            libfdt_bindgen::FDT_ERR_NOPHANDLES => FdtError::NoPhandles,
-            libfdt_bindgen::FDT_ERR_BADFLAGS => FdtError::BadFlags,
-            libfdt_bindgen::FDT_ERR_ALIGNMENT => FdtError::Alignment,
-            _ => FdtError::Unknown(val),
-        })
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub(crate) struct FdtRawResult(c_int);
+
+impl From<c_int> for FdtRawResult {
+    fn from(value: c_int) -> Self {
+        Self(value)
     }
 }
 
-pub(crate) fn fdt_err_expect_zero(val: c_int) -> Result<()> {
-    match fdt_err(val)? {
-        0 => Ok(()),
-        _ => Err(FdtError::Unknown(val)),
+impl TryFrom<FdtRawResult> for c_int {
+    type Error = FdtError;
+
+    fn try_from(res: FdtRawResult) -> Result<Self> {
+        use libfdt_bindgen::{
+            FDT_ERR_ALIGNMENT, FDT_ERR_BADFLAGS, FDT_ERR_BADLAYOUT, FDT_ERR_BADMAGIC,
+            FDT_ERR_BADNCELLS, FDT_ERR_BADOFFSET, FDT_ERR_BADOVERLAY, FDT_ERR_BADPATH,
+            FDT_ERR_BADPHANDLE, FDT_ERR_BADSTATE, FDT_ERR_BADSTRUCTURE, FDT_ERR_BADVALUE,
+            FDT_ERR_BADVERSION, FDT_ERR_EXISTS, FDT_ERR_INTERNAL, FDT_ERR_NOPHANDLES,
+            FDT_ERR_NOSPACE, FDT_ERR_NOTFOUND, FDT_ERR_TRUNCATED,
+        };
+        match res.0 {
+            x if x >= 0 => Ok(x),
+            x if x == -(FDT_ERR_NOTFOUND as c_int) => Err(FdtError::NotFound),
+            x if x == -(FDT_ERR_EXISTS as c_int) => Err(FdtError::Exists),
+            x if x == -(FDT_ERR_NOSPACE as c_int) => Err(FdtError::NoSpace),
+            x if x == -(FDT_ERR_BADOFFSET as c_int) => Err(FdtError::BadOffset),
+            x if x == -(FDT_ERR_BADPATH as c_int) => Err(FdtError::BadPath),
+            x if x == -(FDT_ERR_BADPHANDLE as c_int) => Err(FdtError::BadPhandle),
+            x if x == -(FDT_ERR_BADSTATE as c_int) => Err(FdtError::BadState),
+            x if x == -(FDT_ERR_TRUNCATED as c_int) => Err(FdtError::Truncated),
+            x if x == -(FDT_ERR_BADMAGIC as c_int) => Err(FdtError::BadMagic),
+            x if x == -(FDT_ERR_BADVERSION as c_int) => Err(FdtError::BadVersion),
+            x if x == -(FDT_ERR_BADSTRUCTURE as c_int) => Err(FdtError::BadStructure),
+            x if x == -(FDT_ERR_BADLAYOUT as c_int) => Err(FdtError::BadLayout),
+            x if x == -(FDT_ERR_INTERNAL as c_int) => Err(FdtError::Internal),
+            x if x == -(FDT_ERR_BADNCELLS as c_int) => Err(FdtError::BadNCells),
+            x if x == -(FDT_ERR_BADVALUE as c_int) => Err(FdtError::BadValue),
+            x if x == -(FDT_ERR_BADOVERLAY as c_int) => Err(FdtError::BadOverlay),
+            x if x == -(FDT_ERR_NOPHANDLES as c_int) => Err(FdtError::NoPhandles),
+            x if x == -(FDT_ERR_BADFLAGS as c_int) => Err(FdtError::BadFlags),
+            x if x == -(FDT_ERR_ALIGNMENT as c_int) => Err(FdtError::Alignment),
+            x => Err(FdtError::Unknown(x)),
+        }
     }
 }
 
-pub(crate) fn fdt_err_or_option(val: c_int) -> Result<Option<c_int>> {
-    match fdt_err(val) {
-        Ok(val) => Ok(Some(val)),
-        Err(FdtError::NotFound) => Ok(None),
-        Err(e) => Err(e),
+impl TryFrom<FdtRawResult> for Option<c_int> {
+    type Error = FdtError;
+
+    fn try_from(res: FdtRawResult) -> Result<Self> {
+        match res.try_into() {
+            Ok(n) => Ok(Some(n)),
+            Err(FdtError::NotFound) => Ok(None),
+            Err(e) => Err(e),
+        }
+    }
+}
+
+impl TryFrom<FdtRawResult> for c_uint {
+    type Error = FdtError;
+
+    fn try_from(res: FdtRawResult) -> Result<Self> {
+        Ok(c_int::try_from(res)?.try_into().unwrap())
+    }
+}
+
+impl TryFrom<FdtRawResult> for usize {
+    type Error = FdtError;
+
+    fn try_from(res: FdtRawResult) -> Result<Self> {
+        Ok(c_int::try_from(res)?.try_into().unwrap())
+    }
+}
+
+impl TryFrom<FdtRawResult> for Option<usize> {
+    type Error = FdtError;
+
+    fn try_from(res: FdtRawResult) -> Result<Self> {
+        match res.try_into() {
+            Ok(n) => Ok(Some(n)),
+            Err(FdtError::NotFound) => Ok(None),
+            Err(e) => Err(e),
+        }
+    }
+}
+
+impl TryFrom<FdtRawResult> for () {
+    type Error = FdtError;
+
+    fn try_from(res: FdtRawResult) -> Result<Self> {
+        match res.try_into()? {
+            0 => Ok(()),
+            n => Err(FdtError::Unknown(n)),
+        }
     }
 }