zynq::eth: switch rx and tx descriptor words to vcell

vcell can be initialized cleanly.

Cargo.lock

@@ -75,6 +75,7 @@ dependencies = [
  "linked_list_allocator 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "r0 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "smoltcp 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "vcell 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "volatile-register 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 

Cargo.toml

@@ -19,6 +19,7 @@ default = ["target_zc706"]
 
 [dependencies]
 r0 = "0.2"
+vcell = "0.1"
 volatile-register = "0.2"
 bit_field = "0.10"
 compiler_builtins = { version = "~0.1", default-features = false, features = ["mem", "no-lang-items"]}

src/regs.rs

@@ -2,6 +2,7 @@
 //! svd2rust generates.
 #![allow(unused)]
 
+use vcell::VolatileCell;
 use volatile_register::{RO, WO, RW};
 use bit_field::BitField;
 
@@ -96,6 +97,40 @@ macro_rules! register_rw {
     );
 }
 
+#[doc(hidden)]
+#[macro_export]
+macro_rules! register_vcell {
+    ($mod_name: ident, $struct_name: ident) => (
+        impl crate::regs::RegisterR for $struct_name {
+            type R = $mod_name::Read;
+
+            fn read(&self) -> Self::R {
+                let inner = self.inner.get();
+                $mod_name::Read { inner }
+            }
+        }
+        impl crate::regs::RegisterW for $struct_name {
+            type W = $mod_name::Write;
+
+            fn zeroed() -> $mod_name::Write {
+                $mod_name::Write { inner: 0 }
+            }
+
+            fn write(&mut self, w: Self::W) {
+                self.inner.set(w.inner);
+            }
+        }
+        impl crate::regs::RegisterRW for $struct_name {
+            fn modify<F: FnOnce(Self::R, Self::W) -> Self::W>(&mut self, f: F) {
+                let r = self.read();
+                let w = $mod_name::Write { inner: r.inner };
+                let w = f(r, w);
+                self.write(w);
+            }
+        }
+    );
+}
+
 /// Main macro for register definition
 #[macro_export]
 macro_rules! register {
@@ -118,6 +153,12 @@ macro_rules! register {
         crate::register_w!($mod_name, $struct_name);
         crate::register_rw!($mod_name, $struct_name);
     );
+
+    // Define read-write register
+    ($mod_name: ident, $struct_name: ident, VolatileCell, $inner: ty) => (
+        crate::register_common!($mod_name, $struct_name, VolatileCell<$inner>, $inner);
+        crate::register_vcell!($mod_name, $struct_name);
+    );
 }
 
 /// Define a 1-bit field of a register

src/zynq/eth/rx.rs

@@ -1,4 +1,5 @@
 use core::ops::Deref;
+use vcell::VolatileCell;
 use crate::{register, register_bit, register_bits, regs::*};
 use super::MTU;
 
@@ -19,7 +20,16 @@ pub struct DescEntry {
     word1: DescWord1,
 }
 
-register!(desc_word0, DescWord0, RW, u32);
+impl DescEntry {
+    pub fn zeroed() -> Self {
+        DescEntry {
+            word0: DescWord0 { inner: VolatileCell::new(0) },
+            word1: DescWord1 { inner: VolatileCell::new(0) },
+        }
+    }
+}
+
+register!(desc_word0, DescWord0, VolatileCell, u32);
 register_bit!(desc_word0,
               /// true if owned by software, false if owned by hardware
               used, 0);
@@ -28,7 +38,7 @@ register_bit!(desc_word0,
               wrap, 1);
 register_bits!(desc_word0, address, u32, 2, 31);
 
-register!(desc_word1, DescWord1, RW, u32);
+register!(desc_word1, DescWord1, VolatileCell, u32);
 register_bits!(desc_word1, frame_length_lsbs, u16, 0, 12);
 register_bit!(desc_word1, bad_fcs, 13);
 register_bit!(desc_word1, start_of_frame, 14);

src/zynq/eth/tx.rs

@@ -1,4 +1,5 @@
 use core::ops::{Deref, DerefMut};
+use vcell::VolatileCell;
 use crate::{register, register_bit, register_bits, regs::*};
 use crate::cortex_a9::asm;
 use super::{MTU, regs};
@@ -10,10 +11,10 @@ pub struct DescEntry {
     word1: DescWord1,
 }
 
-register!(desc_word0, DescWord0, RW, u32);
+register!(desc_word0, DescWord0, VolatileCell, u32);
 register_bits!(desc_word0, address, u32, 0, 31);
 
-register!(desc_word1, DescWord1, RW, u32);
+register!(desc_word1, DescWord1, VolatileCell, u32);
 register_bits!(desc_word1, length, u16, 0, 13);
 register_bit!(desc_word1, last_buffer, 15);
 register_bit!(desc_word1, no_crc_append, 16);
@@ -28,6 +29,15 @@ register_bit!(desc_word1,
               /// true if owned by software, false if owned by hardware
               used, 31);
 
+impl DescEntry {
+    pub fn zeroed() -> Self {
+        DescEntry {
+            word0: DescWord0 { inner: VolatileCell::new(0) },
+            word1: DescWord1 { inner: VolatileCell::new(0) },
+        }
+    }
+}
+
 /// Number of descriptors
 pub const DESCS: usize = 8;