| Message ID | 20250326171411.590681-10-remo@buenzli.dev (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | More Rust bindings for device property reads | expand |
On Wed, Mar 26, 2025 at 12:13 PM Remo Senekowitsch Wrote: > +/// A helper for reading device properties. > +/// > +/// Use [Self::required] if a missing property is considered a bug and > +/// [Self::optional] otherwise. > +/// > +/// For convenience, [Self::or] and [Self::or_default] are provided. > +pub struct PropertyGuard<'fwnode, 'name, T> { nit: when linking items in rustdoc comments you should suround them like [`this`] Andrew
On Wed, Mar 26, 2025 at 06:13:48PM +0100, Remo Senekowitsch wrote: > Forcing users to specify whether a property is supposed to be required > or not allows us to move error logging of missing required properties > into core, preventing a lot of boilerplate in drivers. We'll want to squash this one too. > > Signed-off-by: Remo Senekowitsch <remo@buenzli.dev> > --- > rust/kernel/property.rs | 146 ++++++++++++++++++++++++++++++++++------ > 1 file changed, 127 insertions(+), 19 deletions(-) > > diff --git a/rust/kernel/property.rs b/rust/kernel/property.rs > index f1d0a33ba..e4f0e5f97 100644 > --- a/rust/kernel/property.rs > +++ b/rust/kernel/property.rs > @@ -42,7 +42,11 @@ pub fn property_match_string(&self, name: &CStr, match_str: &CStr) -> Result<usi > } > > /// Returns firmware property `name` integer array values in a KVec > - pub fn property_read_array_vec<T: Integer>(&self, name: &CStr, len: usize) -> Result<KVec<T>> { > + pub fn property_read_array_vec<'fwnode, 'name, T: Integer>( > + &'fwnode self, > + name: &'name CStr, > + len: usize, > + ) -> Result<PropertyGuard<'fwnode, 'name, KVec<T>>> { > self.fwnode().property_read_array_vec(name, len) > } > > @@ -52,12 +56,18 @@ pub fn property_count_elem<T: Integer>(&self, name: &CStr) -> Result<usize> { > } > > /// Returns firmware property `name` integer scalar value > - pub fn property_read<T: Property>(&self, name: &CStr) -> Result<T> { > + pub fn property_read<'fwnode, 'name, T: Property>( > + &'fwnode self, > + name: &'name CStr, > + ) -> PropertyGuard<'fwnode, 'name, T> { > self.fwnode().property_read(name) > } > > /// Returns first matching named child node handle. > - pub fn get_child_by_name(&self, name: &CStr) -> Option<ARef<FwNode>> { > + pub fn get_child_by_name<'fwnode, 'name>( > + &'fwnode self, > + name: &'name CStr, > + ) -> PropertyGuard<'fwnode, 'name, ARef<FwNode>> { > self.fwnode().get_child_by_name(name) > } While child nodes can be required or optional, it's a bit less common to be optional. There error message on missing required child nodes is going to be a bit misleading saying 'property'. So maybe don't do the PropertyGuard on child node handling? > > @@ -132,12 +142,16 @@ pub fn property_match_string(&self, name: &CStr, match_str: &CStr) -> Result<usi > } > > /// Returns firmware property `name` integer array values in a KVec > - pub fn property_read_array_vec<T: Integer>(&self, name: &CStr, len: usize) -> Result<KVec<T>> { > + pub fn property_read_array_vec<'fwnode, 'name, T: Integer>( > + &'fwnode self, > + name: &'name CStr, > + len: usize, > + ) -> Result<PropertyGuard<'fwnode, 'name, KVec<T>>> { > let mut val: KVec<T> = KVec::with_capacity(len, GFP_KERNEL)?; > > // SAFETY: `name` is non-null and null-terminated. `self.as_raw` is valid > // because `self` is valid. `val.as_ptr` is valid because `val` is valid. > - to_result(unsafe { > + let err = unsafe { > bindings::fwnode_property_read_int_array( > self.as_raw(), > name.as_char_ptr(), > @@ -145,11 +159,19 @@ pub fn property_read_array_vec<T: Integer>(&self, name: &CStr, len: usize) -> Re > val.as_ptr() as *mut c_void, > len, > ) > - })?; > - > - // SAFETY: fwnode_property_read_int_array() writes exactly `len` entries on success > - unsafe { val.set_len(len) } > - Ok(val) > + }; > + let res = if err < 0 { > + Err(Error::from_errno(err)) > + } else { > + // SAFETY: fwnode_property_read_int_array() writes exactly `len` entries on success > + unsafe { val.set_len(len) } > + Ok(val) > + }; > + Ok(PropertyGuard { > + inner: res, > + fwnode: self, > + name, > + }) > } > > /// Returns integer array length for firmware property `name` > @@ -194,24 +216,42 @@ pub fn property_count_elem<T: Integer>(&self, name: &CStr) -> Result<usize> { > /// # use crate::{device::Device, types::CString}; > /// fn examples(dev: &Device) -> Result { > /// let fwnode = dev.fwnode(); > - /// let b: bool = fwnode.property_read("some-bool")?; > - /// let s: CString = fwnode.property_read("some-str")?; > + /// let b: bool = fwnode.property_read("some-bool").required()?; > + /// if let Some(s) = fwnode.property_read::<CString>("some-str").optional() { > + /// // ... > + /// } > /// } > /// ``` > - pub fn property_read<T: Property>(&self, name: &CStr) -> Result<T> { > - T::read(&self, name) > + pub fn property_read<'fwnode, 'name, T: Property>( > + &'fwnode self, > + name: &'name CStr, > + ) -> PropertyGuard<'fwnode, 'name, T> { > + PropertyGuard { > + inner: T::read(&self, name), > + fwnode: self, > + name, > + } > } > > /// Returns first matching named child node handle. > - pub fn get_child_by_name(&self, name: &CStr) -> Option<ARef<Self>> { > + pub fn get_child_by_name<'fwnode, 'name>( > + &'fwnode self, > + name: &'name CStr, > + ) -> PropertyGuard<'fwnode, 'name, ARef<Self>> { > // SAFETY: `self` and `name` are valid. > let child = > unsafe { bindings::fwnode_get_named_child_node(self.as_raw(), name.as_char_ptr()) }; > - if child.is_null() { > - return None; > + let res = if child.is_null() { > + Err(ENOENT) > + } else { > + // SAFETY: `fwnode_get_named_child_node` returns a pointer with refcount incremented. > + Ok(unsafe { Self::from_raw(child) }) > + }; > + PropertyGuard { > + inner: res, > + fwnode: self, > + name, > } > - // SAFETY: `fwnode_get_named_child_node` returns a pointer with refcount incremented. > - Some(unsafe { Self::from_raw(child) }) > } > > /// Returns an iterator over a node's children. > @@ -365,3 +405,71 @@ pub enum NArgs<'a> { > /// The known number of arguments. > N(u32), > } > + > +/// A helper for reading device properties. > +/// > +/// Use [Self::required] if a missing property is considered a bug and > +/// [Self::optional] otherwise. > +/// > +/// For convenience, [Self::or] and [Self::or_default] are provided. > +pub struct PropertyGuard<'fwnode, 'name, T> { > + /// The result of reading the property. > + inner: Result<T>, > + /// The fwnode of the property, used for logging in the "required" case. > + fwnode: &'fwnode FwNode, > + /// The name of the property, used for logging in the "required" case. > + name: &'name CStr, > +} > + > +impl<T> PropertyGuard<'_, '_, T> { > + /// Access the property, indicating it is required. > + /// > + /// If the property is not present, the error is automatically logged. If a > + /// missing property is not an error, use [Self::optional] instead. > + pub fn required(self) -> Result<T> { > + if self.inner.is_err() { > + // Get the device associated with the fwnode for device-associated > + // logging. > + // TODO: Are we allowed to do this? The field `fwnode_handle.dev` > + // has a somewhat vague comment, which could mean we're not > + // supposed to access it: > + // https://elixir.bootlin.com/linux/v6.13.6/source/include/linux/fwnode.h#L51 > + // SAFETY: According to the invariant of FwNode, it is valid. > + let dev = unsafe { (*self.fwnode.as_raw()).dev }; > + > + if dev.is_null() { > + pr_err!("property '{}' is missing\n", self.name); We should print the node path in this case (and perhaps both cases). We have "%pfw" printf format specifier for C. We're going to need the same for rust. > + } else { > + // SAFETY: If dev is not null, it points to a valid device. > + let dev: &Device = unsafe { &*dev.cast() }; > + dev_err!(dev, "property '{}' is missing\n", self.name); > + }; > + } > + self.inner > + } > + > + /// Access the property, indicating it is optional. > + /// > + /// In contrast to [Self::required], no error message is logged if the > + /// property is not present. > + pub fn optional(self) -> Option<T> { > + self.inner.ok() > + } > + > + /// Access the property or the specified default value. > + /// > + /// Do not pass a sentinel value as default to detect a missing property. > + /// Use [Self::required] or [Self::optional] instead. > + pub fn or(self, default: T) -> T { > + self.inner.unwrap_or(default) > + } > +} > + > +impl<T: Default> PropertyGuard<'_, '_, T> { > + /// Access the property or a default value. > + /// > + /// Use [Self::or] to specify a custom default value. > + pub fn or_default(self) -> T { > + self.inner.unwrap_or_default() > + } > +} > -- > 2.49.0 >
diff --git a/rust/kernel/property.rs b/rust/kernel/property.rs index f1d0a33ba..e4f0e5f97 100644 --- a/rust/kernel/property.rs +++ b/rust/kernel/property.rs @@ -42,7 +42,11 @@ pub fn property_match_string(&self, name: &CStr, match_str: &CStr) -> Result<usi } /// Returns firmware property `name` integer array values in a KVec - pub fn property_read_array_vec<T: Integer>(&self, name: &CStr, len: usize) -> Result<KVec<T>> { + pub fn property_read_array_vec<'fwnode, 'name, T: Integer>( + &'fwnode self, + name: &'name CStr, + len: usize, + ) -> Result<PropertyGuard<'fwnode, 'name, KVec<T>>> { self.fwnode().property_read_array_vec(name, len) } @@ -52,12 +56,18 @@ pub fn property_count_elem<T: Integer>(&self, name: &CStr) -> Result<usize> { } /// Returns firmware property `name` integer scalar value - pub fn property_read<T: Property>(&self, name: &CStr) -> Result<T> { + pub fn property_read<'fwnode, 'name, T: Property>( + &'fwnode self, + name: &'name CStr, + ) -> PropertyGuard<'fwnode, 'name, T> { self.fwnode().property_read(name) } /// Returns first matching named child node handle. - pub fn get_child_by_name(&self, name: &CStr) -> Option<ARef<FwNode>> { + pub fn get_child_by_name<'fwnode, 'name>( + &'fwnode self, + name: &'name CStr, + ) -> PropertyGuard<'fwnode, 'name, ARef<FwNode>> { self.fwnode().get_child_by_name(name) } @@ -132,12 +142,16 @@ pub fn property_match_string(&self, name: &CStr, match_str: &CStr) -> Result<usi } /// Returns firmware property `name` integer array values in a KVec - pub fn property_read_array_vec<T: Integer>(&self, name: &CStr, len: usize) -> Result<KVec<T>> { + pub fn property_read_array_vec<'fwnode, 'name, T: Integer>( + &'fwnode self, + name: &'name CStr, + len: usize, + ) -> Result<PropertyGuard<'fwnode, 'name, KVec<T>>> { let mut val: KVec<T> = KVec::with_capacity(len, GFP_KERNEL)?; // SAFETY: `name` is non-null and null-terminated. `self.as_raw` is valid // because `self` is valid. `val.as_ptr` is valid because `val` is valid. - to_result(unsafe { + let err = unsafe { bindings::fwnode_property_read_int_array( self.as_raw(), name.as_char_ptr(), @@ -145,11 +159,19 @@ pub fn property_read_array_vec<T: Integer>(&self, name: &CStr, len: usize) -> Re val.as_ptr() as *mut c_void, len, ) - })?; - - // SAFETY: fwnode_property_read_int_array() writes exactly `len` entries on success - unsafe { val.set_len(len) } - Ok(val) + }; + let res = if err < 0 { + Err(Error::from_errno(err)) + } else { + // SAFETY: fwnode_property_read_int_array() writes exactly `len` entries on success + unsafe { val.set_len(len) } + Ok(val) + }; + Ok(PropertyGuard { + inner: res, + fwnode: self, + name, + }) } /// Returns integer array length for firmware property `name` @@ -194,24 +216,42 @@ pub fn property_count_elem<T: Integer>(&self, name: &CStr) -> Result<usize> { /// # use crate::{device::Device, types::CString}; /// fn examples(dev: &Device) -> Result { /// let fwnode = dev.fwnode(); - /// let b: bool = fwnode.property_read("some-bool")?; - /// let s: CString = fwnode.property_read("some-str")?; + /// let b: bool = fwnode.property_read("some-bool").required()?; + /// if let Some(s) = fwnode.property_read::<CString>("some-str").optional() { + /// // ... + /// } /// } /// ``` - pub fn property_read<T: Property>(&self, name: &CStr) -> Result<T> { - T::read(&self, name) + pub fn property_read<'fwnode, 'name, T: Property>( + &'fwnode self, + name: &'name CStr, + ) -> PropertyGuard<'fwnode, 'name, T> { + PropertyGuard { + inner: T::read(&self, name), + fwnode: self, + name, + } } /// Returns first matching named child node handle. - pub fn get_child_by_name(&self, name: &CStr) -> Option<ARef<Self>> { + pub fn get_child_by_name<'fwnode, 'name>( + &'fwnode self, + name: &'name CStr, + ) -> PropertyGuard<'fwnode, 'name, ARef<Self>> { // SAFETY: `self` and `name` are valid. let child = unsafe { bindings::fwnode_get_named_child_node(self.as_raw(), name.as_char_ptr()) }; - if child.is_null() { - return None; + let res = if child.is_null() { + Err(ENOENT) + } else { + // SAFETY: `fwnode_get_named_child_node` returns a pointer with refcount incremented. + Ok(unsafe { Self::from_raw(child) }) + }; + PropertyGuard { + inner: res, + fwnode: self, + name, } - // SAFETY: `fwnode_get_named_child_node` returns a pointer with refcount incremented. - Some(unsafe { Self::from_raw(child) }) } /// Returns an iterator over a node's children. @@ -365,3 +405,71 @@ pub enum NArgs<'a> { /// The known number of arguments. N(u32), } + +/// A helper for reading device properties. +/// +/// Use [Self::required] if a missing property is considered a bug and +/// [Self::optional] otherwise. +/// +/// For convenience, [Self::or] and [Self::or_default] are provided. +pub struct PropertyGuard<'fwnode, 'name, T> { + /// The result of reading the property. + inner: Result<T>, + /// The fwnode of the property, used for logging in the "required" case. + fwnode: &'fwnode FwNode, + /// The name of the property, used for logging in the "required" case. + name: &'name CStr, +} + +impl<T> PropertyGuard<'_, '_, T> { + /// Access the property, indicating it is required. + /// + /// If the property is not present, the error is automatically logged. If a + /// missing property is not an error, use [Self::optional] instead. + pub fn required(self) -> Result<T> { + if self.inner.is_err() { + // Get the device associated with the fwnode for device-associated + // logging. + // TODO: Are we allowed to do this? The field `fwnode_handle.dev` + // has a somewhat vague comment, which could mean we're not + // supposed to access it: + // https://elixir.bootlin.com/linux/v6.13.6/source/include/linux/fwnode.h#L51 + // SAFETY: According to the invariant of FwNode, it is valid. + let dev = unsafe { (*self.fwnode.as_raw()).dev }; + + if dev.is_null() { + pr_err!("property '{}' is missing\n", self.name); + } else { + // SAFETY: If dev is not null, it points to a valid device. + let dev: &Device = unsafe { &*dev.cast() }; + dev_err!(dev, "property '{}' is missing\n", self.name); + }; + } + self.inner + } + + /// Access the property, indicating it is optional. + /// + /// In contrast to [Self::required], no error message is logged if the + /// property is not present. + pub fn optional(self) -> Option<T> { + self.inner.ok() + } + + /// Access the property or the specified default value. + /// + /// Do not pass a sentinel value as default to detect a missing property. + /// Use [Self::required] or [Self::optional] instead. + pub fn or(self, default: T) -> T { + self.inner.unwrap_or(default) + } +} + +impl<T: Default> PropertyGuard<'_, '_, T> { + /// Access the property or a default value. + /// + /// Use [Self::or] to specify a custom default value. + pub fn or_default(self) -> T { + self.inner.unwrap_or_default() + } +}
Forcing users to specify whether a property is supposed to be required or not allows us to move error logging of missing required properties into core, preventing a lot of boilerplate in drivers. Signed-off-by: Remo Senekowitsch <remo@buenzli.dev> --- rust/kernel/property.rs | 146 ++++++++++++++++++++++++++++++++++------ 1 file changed, 127 insertions(+), 19 deletions(-)