Merge pull request #788 from rust-embedded/bits

generic safe/unsafe W::bits

Author: Emilgardis

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/).
 ## [Unreleased]
 
 - Bump MSRV to 1.74
+- generic unsafe `W::bits` + safe `W::set`
 - Add `base-address-shift` config flag
 - Fix case changing bugs, add `--ident-format` (`-f`) option flag
 

src/generate/generic.rs

@@ -67,6 +67,9 @@ pub trait Readable: RegisterSpec {}
 ///
 /// Registers marked with `Readable` can be also be `modify`'ed.
 pub trait Writable: RegisterSpec {
+    /// Is it safe to write any bits to register
+    type Safety;
+
     /// Specifies the register bits that are not changed if you pass `1` and are changed if you pass `0`
     const ZERO_TO_MODIFY_FIELDS_BITMAP: Self::Ux;
 
@@ -390,6 +393,27 @@ where
 /// Used as an argument to the closures in the `write` and `modify` methods of the register.
 pub type W<REG> = raw::W<REG>;
 
+impl<REG: Writable> W<REG> {
+    /// Writes raw bits to the register.
+    ///
+    /// # Safety
+    ///
+    /// Passing incorrect value can cause undefined behaviour. See reference manual
+    #[inline(always)]
+    pub unsafe fn bits(&mut self, bits: REG::Ux) -> &mut Self {
+        self.bits = bits;
+        self
+    }
+}
+impl<REG> W<REG> where REG: Writable<Safety = Safe> {
+    /// Writes raw bits to the register.
+    #[inline(always)]
+    pub fn set(&mut self, bits: REG::Ux) -> &mut Self {
+        self.bits = bits;
+        self
+    }
+}
+
 /// Field reader.
 ///
 /// Result of the `read` methods of fields.
@@ -445,9 +469,9 @@ impl<FI> BitReader<FI> {
     }
 }
 
-#[doc(hidden)]
+/// Marker for register/field writers which can take any value of specified width
 pub struct Safe;
-#[doc(hidden)]
+/// You should check that value is allowed to pass to register/field writer marked with this
 pub struct Unsafe;
 
 /// Write field Proxy with unsafe `bits`

src/generate/register.rs

@@ -26,7 +26,7 @@ fn regspec(name: &str, config: &Config, span: Span) -> Ident {
 }
 
 fn field_accessor(name: &str, config: &Config, span: Span) -> Ident {
-    const INTERNALS: [&str; 1] = ["bits"];
+    const INTERNALS: [&str; 2] = ["bits", "set"];
     let sc = config
         .ident_formats
         .get("field_accessor")
@@ -355,44 +355,6 @@ pub fn render_register_mod(
 
         mod_items.extend(w_impl_items);
 
-        // the writer can be safe if:
-        // * there is a single field that covers the entire register
-        // * that field can represent all values
-        // * the write constraints of the register allow full range of values
-        let can_write_safe = !unsafety(
-            register
-                .fields
-                .as_ref()
-                .and_then(|fields| fields.first())
-                .and_then(|field| field.write_constraint)
-                .as_ref(),
-            rsize,
-        ) || !unsafety(register.write_constraint.as_ref(), rsize);
-
-        if can_write_safe {
-            mod_items.extend(quote! {
-                #[doc = "Writes raw bits to the register."]
-                #[inline(always)]
-                pub fn bits(&mut self, bits: #rty) -> &mut Self {
-                    self.bits = bits;
-                    self
-                }
-            });
-        } else {
-            mod_items.extend(quote! {
-                /// Writes raw bits to the register.
-                ///
-                /// # Safety
-                ///
-                /// Passing incorrect value can cause undefined behaviour. See reference manual
-                #[inline(always)]
-                pub unsafe fn bits(&mut self, bits: #rty) -> &mut Self {
-                    self.bits = bits;
-                    self
-                }
-            });
-        }
-
         close.to_tokens(&mut mod_items);
     }
 
@@ -425,6 +387,22 @@ pub fn render_register_mod(
         });
     }
     if can_write {
+        // the writer can be safe if:
+        // * there is a single field that covers the entire register
+        // * that field can represent all values
+        // * the write constraints of the register allow full range of values
+        let can_write_safe = !unsafety(
+            register
+                .fields
+                .as_ref()
+                .and_then(|fields| fields.first())
+                .and_then(|field| field.write_constraint)
+                .as_ref(),
+            rsize,
+        ) || !unsafety(register.write_constraint.as_ref(), rsize);
+        let safe_ty = if can_write_safe { "Safe" } else { "Unsafe" };
+        let safe_ty = Ident::new(safe_ty, span);
+
         let doc = format!("`write(|w| ..)` method takes [`{mod_ty}::W`](W) writer structure",);
 
         let zero_to_modify_fields_bitmap = util::hex(zero_to_modify_fields_bitmap);
@@ -433,6 +411,7 @@ pub fn render_register_mod(
         mod_items.extend(quote! {
             #[doc = #doc]
             impl crate::Writable for #regspec_ty {
+                type Safety = crate::#safe_ty;
                 const ZERO_TO_MODIFY_FIELDS_BITMAP: #rty = #zero_to_modify_fields_bitmap;
                 const ONE_TO_MODIFY_FIELDS_BITMAP: #rty = #one_to_modify_fields_bitmap;
             }