Add two new public methods `display_name` and `display_path` to
`FwNode`. They can be used by driver authors for logging purposes. In
addition, they will be used by core property abstractions for automatic
logging, for example when a driver attempts to read a required but
missing property.
Signed-off-by: Remo Senekowitsch <remo@buenzli.dev>
---
rust/kernel/device/property.rs | 75 ++++++++++++++++++++++++++++++++++
1 file changed, 75 insertions(+)
diff --git a/rust/kernel/device/property.rs b/rust/kernel/device/property.rs
index 71a0605b8ecad..09c38775b2354 100644
--- a/rust/kernel/device/property.rs
+++ b/rust/kernel/device/property.rs
@@ -32,6 +32,81 @@ pub(crate) fn as_raw(&self) -> *mut bindings::fwnode_handle {
self.0.get()
}
+ /// Returns an object that implements [`Display`](core::fmt::Display) for
+ /// printing the name of a node.
+ pub fn display_name(&self) -> impl core::fmt::Display + '_ {
+ struct FwNodeDisplayName<'a>(&'a FwNode);
+
+ impl core::fmt::Display for FwNodeDisplayName<'_> {
+ fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+ // SAFETY: `self` is valid by its type invariant.
+ let name = unsafe { bindings::fwnode_get_name(self.0.as_raw()) };
+ if name.is_null() {
+ return Ok(());
+ }
+ // SAFETY:
+ // - `fwnode_get_name` returns null or a valid C string.
+ // - `name` was checked to be non-null.
+ let name = unsafe { CStr::from_char_ptr(name) };
+ write!(f, "{name}")
+ }
+ }
+
+ FwNodeDisplayName(self)
+ }
+
+ /// Returns an object that implements [`Display`](core::fmt::Display) for
+ /// printing the full path of a node.
+ pub fn display_path(&self) -> impl core::fmt::Display + '_ {
+ struct FwNodeDisplayPath<'a>(&'a FwNode);
+
+ impl core::fmt::Display for FwNodeDisplayPath<'_> {
+ fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+ // The logic here is the same as the one in lib/vsprintf.c
+ // (fwnode_full_name_string).
+
+ // SAFETY: `self.0.as_raw()` is valid by its type invariant.
+ let num_parents = unsafe { bindings::fwnode_count_parents(self.0.as_raw()) };
+
+ for depth in (0..=num_parents).rev() {
+ let fwnode = if depth == 0 {
+ self.0.as_raw()
+ } else {
+ // SAFETY: `self.0.as_raw()` is valid.
+ unsafe { bindings::fwnode_get_nth_parent(self.0.as_raw(), depth) }
+ };
+
+ // SAFETY: `fwnode` is valid, it is either `self.0.as_raw()`
+ // or the return value of `bindings::fwnode_get_nth_parent`
+ // which returns a valid pointer to a `fwnode_handle` if the
+ // provided depth is within the valid range, which we know
+ // to be true.
+ let prefix = unsafe { bindings::fwnode_get_name_prefix(fwnode) };
+ if !prefix.is_null() {
+ // SAFETY: `fwnode_get_name_prefix` returns null or a
+ // valid C string.
+ let prefix = unsafe { CStr::from_char_ptr(prefix) };
+ write!(f, "{prefix}")?;
+ }
+ write!(f, "{}", self.0.display_name())?;
+
+ if depth != 0 {
+ // SAFETY:
+ // - `fwnode` is valid, because `depth` is
+ // a valid depth of a parent of `self.0.as_raw()`.
+ // - `fwnode_get_nth_parent` increments the refcount and
+ // we are responsible to decrement it.
+ unsafe { bindings::fwnode_handle_put(fwnode) }
+ }
+ }
+
+ Ok(())
+ }
+ }
+
+ FwNodeDisplayPath(self)
+ }
+
/// Checks if property is present or not.
pub fn property_present(&self, name: &CStr) -> bool {
// SAFETY: By the invariant of `CStr`, `name` is null-terminated.
--
2.49.0On Sat, May 24, 2025 at 09:22:27PM +0200, Remo Senekowitsch wrote:
> + /// Returns an object that implements [`Display`](core::fmt::Display) for
> + /// printing the full path of a node.
> + pub fn display_path(&self) -> impl core::fmt::Display + '_ {
While testing the code I found the following buggy print statement:
"test-device@2/test-device@2/test-device@2/test-device@2: property 'test,u32-required-prop' is missing"
and I think the following changes fix this:
> + struct FwNodeDisplayPath<'a>(&'a FwNode);
> +
> + impl core::fmt::Display for FwNodeDisplayPath<'_> {
> + fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
> + // The logic here is the same as the one in lib/vsprintf.c
> + // (fwnode_full_name_string).
> +
> + // SAFETY: `self.0.as_raw()` is valid by its type invariant.
> + let num_parents = unsafe { bindings::fwnode_count_parents(self.0.as_raw()) };
> +
> + for depth in (0..=num_parents).rev() {
> + let fwnode = if depth == 0 {
> + self.0.as_raw()
self.0
> + } else {
> + // SAFETY: `self.0.as_raw()` is valid.
> + unsafe { bindings::fwnode_get_nth_parent(self.0.as_raw(), depth) }
let ptr = unsafe { bindings::fwnode_get_nth_parent(self.0.as_raw(), depth) };
FwNode::as_ref(ptr)
where FwNode::as_ref() is
unsafe fn as_ref<'a>(ptr: *mut bindings::fwnode_handle) -> &'a Self
> + };
> +
> + // SAFETY: `fwnode` is valid, it is either `self.0.as_raw()`
> + // or the return value of `bindings::fwnode_get_nth_parent`
> + // which returns a valid pointer to a `fwnode_handle` if the
> + // provided depth is within the valid range, which we know
> + // to be true.
> + let prefix = unsafe { bindings::fwnode_get_name_prefix(fwnode) };
> + if !prefix.is_null() {
> + // SAFETY: `fwnode_get_name_prefix` returns null or a
> + // valid C string.
> + let prefix = unsafe { CStr::from_char_ptr(prefix) };
> + write!(f, "{prefix}")?;
> + }
> + write!(f, "{}", self.0.display_name())?;
write!(f, "{}", fwnode.0.display_name())?;
Otherwise we always write the name of self, no matter the actual parent depth.
> +
> + if depth != 0 {
> + // SAFETY:
> + // - `fwnode` is valid, because `depth` is
> + // a valid depth of a parent of `self.0.as_raw()`.
> + // - `fwnode_get_nth_parent` increments the refcount and
> + // we are responsible to decrement it.
> + unsafe { bindings::fwnode_handle_put(fwnode) }
> + }
> + }
> +
> + Ok(())
> + }
> + }
> +
> + FwNodeDisplayPath(self)
> + }
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