Mark pipe descriptor register memory as volatile.

Most of the values in the descriptor memory can be modified by the
hardware, so we need to tell Rust that.

Also, refactor the common register setup code into `register.rs`.

9 files changed, 185 insertions, 324 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 8d37175..869801c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,6 +16,7 @@ starb = "~0.3"
 log = "~0.4"
 embedded-hal = "~0.2"
 atsamd-hal = "~0.7"
+vcell = "~0.1"
 
 [dev-dependencies.atsamd-hal]
 version = "~0.7"
diff --git a/src/pipe.rs b/src/pipe.rs
index 3715149..84e4435 100644
--- a/src/pipe.rs
+++ b/src/pipe.rs
@@ -6,6 +6,7 @@ pub mod ctrl_pipe;
 pub mod ext_reg;
 #[allow(unused)]
 pub mod pck_size;
+pub mod register;
 #[allow(unused)]
 pub mod status_bk;
 #[allow(unused)]
@@ -728,7 +729,7 @@ impl PipeDesc {
     }
 }
 
-#[repr(C, packed)]
+#[repr(C)]
 // 16 bytes per bank.
 pub(crate) struct BankDesc {
     pub addr: Addr,
diff --git a/src/pipe/addr.rs b/src/pipe/addr.rs
index d71ee2d..81b6bec 100644
--- a/src/pipe/addr.rs
+++ b/src/pipe/addr.rs
@@ -1,60 +1,29 @@
+use super::register::{Readable, Register, Writable, R as GenR, W as GenW};
+
 /// § 32.8.7.2
 /// Address of the Data Buffer.
 ///
 /// Offset: 0x00 & 0x10
 /// Reset: 0xxxxxxxxx
 /// Property: NA
-#[derive(Clone, Copy, Debug)]
-#[repr(C, packed)]
-pub struct Addr(u32);
-
-pub struct R {
-    bits: u32,
-}
-
-pub struct W {
-    bits: u32,
-}
-
-impl Addr {
-    pub fn read(self) -> R {
-        R { bits: self.0 }
-    }
-
-    pub fn write<F>(&mut self, f: F)
-    where
-        F: FnOnce(&mut W) -> &mut W,
-    {
-        let mut w = W { bits: self.0 };
-        f(&mut w);
-        self.0 = w.bits;
-    }
+pub type Addr = Register<u32, _Addr>;
+impl Readable for Addr {}
+impl Writable for Addr {}
 
-    pub fn modify<F>(&mut self, f: F)
-    where
-        for<'w> F: FnOnce(&R, &'w mut W) -> &'w mut W,
-    {
-        let r = R { bits: self.0 };
-        let mut w = W { bits: self.0 };
-        f(&r, &mut w);
-        self.0 = w.bits;
-    }
-}
+pub type R = GenR<u32, Addr>;
+pub type W = GenW<u32, Addr>;
 
-impl From<u32> for Addr {
-    fn from(v: u32) -> Self {
-        Self(v)
-    }
-}
+pub struct _Addr;
 
 impl R {
-    /// Value in raw bits.
-    pub fn bits(&self) -> u32 {
-        self.bits
+    pub fn addr(&self) -> AddrR {
+        AddrR::new(self.bits)
     }
+}
 
-    pub fn addr(&self) -> AddrR {
-        AddrR(self.bits)
+impl W {
+    pub fn addr(&mut self) -> AddrW {
+        AddrW { w: self }
     }
 }
 
@@ -63,36 +32,14 @@ impl R {
 /// These bits define the data pointer address as an absolute double
 /// word address in RAM. The two least significant bits must be zero
 /// to ensure the descriptor is 32-bit aligned.
-pub struct AddrR(u32);
-impl AddrR {
-    pub fn bits(&self) -> u32 {
-        self.0
-    }
-}
-
-impl W {
-    /// Write raw bits.
-    pub unsafe fn bits(&mut self, v: u32) -> &mut Self {
-        self.bits = v;
-        self
-    }
-
-    pub fn addr(&mut self) -> AddrW {
-        AddrW { w: self }
-    }
-}
+pub type AddrR = GenR<u32, Addr>;
 
 pub struct AddrW<'a> {
     w: &'a mut W,
 }
+
 impl<'a> AddrW<'a> {
-    pub unsafe fn bits(self, v: u32) -> &'a mut W {
-        // Address must be 32-bit aligned. cf §32.8.7.2 of SAMD21 data
-        // sheet.
-        debug_assert!(v.trailing_zeros() >= 2);
-        self.w.bits = v;
-        self.w
+    pub unsafe fn bits(self, bits: u32) -> &'a mut W {
+        self.w.bits(bits)
     }
-
-    // TODO: "safe" method take a pointer instead of raw u32
 }
diff --git a/src/pipe/ctrl_pipe.rs b/src/pipe/ctrl_pipe.rs
index 360a0e7..5db00c1 100644
--- a/src/pipe/ctrl_pipe.rs
+++ b/src/pipe/ctrl_pipe.rs
@@ -1,57 +1,20 @@
+use super::register::{Readable, Register, Writable, R as GenR, W as GenW};
+
 /// Host Control Pipe.
 ///
 /// Offset: 0x0c
 /// Reset: 0xXXXX
 /// Property: PAC Write-Protection, Write-Synchronized, Read-Synchronized
-#[derive(Clone, Copy, Debug)]
-#[repr(C, packed)]
-pub struct CtrlPipe(u16);
-
-pub struct R {
-    bits: u16,
-}
-
-pub struct W {
-    bits: u16,
-}
-
-impl CtrlPipe {
-    pub fn read(self) -> R {
-        R { bits: self.0 }
-    }
-
-    pub fn write<F>(&mut self, f: F)
-    where
-        F: FnOnce(&mut W) -> &mut W,
-    {
-        let mut w = W { bits: self.0 };
-        f(&mut w);
-        self.0 = w.bits;
-    }
+pub type CtrlPipe = Register<u16, _CtrlPipe>;
+impl Readable for CtrlPipe {}
+impl Writable for CtrlPipe {}
 
-    pub fn modify<F>(&mut self, f: F)
-    where
-        for<'w> F: FnOnce(&R, &'w mut W) -> &'w mut W,
-    {
-        let r = R { bits: self.0 };
-        let mut w = W { bits: self.0 };
-        f(&r, &mut w);
-        self.0 = w.bits;
-    }
-}
+pub type R = GenR<u16, CtrlPipe>;
+pub type W = GenW<u16, CtrlPipe>;
 
-impl From<u16> for CtrlPipe {
-    fn from(v: u16) -> Self {
-        Self(v)
-    }
-}
+pub struct _CtrlPipe;
 
 impl R {
-    /// Value in raw bits.
-    pub fn bits(&self) -> u16 {
-        self.bits
-    }
-
     pub fn permax(&self) -> PErMaxR {
         let bits = {
             const POS: u8 = 12;
@@ -115,13 +78,6 @@ impl PDAddrR {
 }
 
 impl W {
-    /// Write raw bits.
-
-    pub unsafe fn bits(&mut self, v: u16) -> &mut Self {
-        self.bits = v;
-        self
-    }
-
     pub fn permax(&mut self) -> PErMaxW {
         PErMaxW { w: self }
     }
diff --git a/src/pipe/ext_reg.rs b/src/pipe/ext_reg.rs
index cd2a8dc..95a8f04 100644
--- a/src/pipe/ext_reg.rs
+++ b/src/pipe/ext_reg.rs
@@ -1,48 +1,21 @@
+use super::register::{Readable, Register, Writable, R as GenR, W as GenW};
+
 /// §32.8.7.4
 /// Extended Register.
 ///
 /// Offset: 0x08
 /// Reset: 0xxxxxxxx
 /// Property: NA
-#[derive(Clone, Copy, Debug)]
-#[repr(C, packed)]
-pub(crate) struct ExtReg(u16);
-
-pub(crate) struct R {
-    bits: u16,
-}
-
-pub(crate) struct W {
-    bits: u16,
-}
-
-impl ExtReg {
-    pub fn read(self) -> R {
-        R { bits: self.0 }
-    }
+pub type ExtReg = Register<u16, _ExtReg>;
+impl Readable for ExtReg {}
+impl Writable for ExtReg {}
 
-    pub fn write<F>(&mut self, f: F)
-    where
-        F: FnOnce(&mut W) -> &mut W,
-    {
-        let mut w = W { bits: self.0 };
-        f(&mut w);
-        self.0 = w.bits;
-    }
-}
+pub type R = GenR<u16, ExtReg>;
+pub type W = GenW<u16, ExtReg>;
 
-impl From<u16> for ExtReg {
-    fn from(v: u16) -> Self {
-        Self(v)
-    }
-}
+pub struct _ExtReg;
 
 impl R {
-    /// Value in raw bits.
-    pub fn bits(&self) -> u16 {
-        self.bits
-    }
-
     pub fn variable(&self) -> VariableR {
         let bits = {
             const POS: u8 = 4;
@@ -89,7 +62,7 @@ impl R {
 /// in the reference document ENGINEERING CHANGE NOTICE, USB 2.0 Link
 /// Power Management Addendum" and "Table X-X1 in Errata for ECN USB
 /// 2.0 Link Power Management.
-pub(crate) struct VariableR(u16);
+pub struct VariableR(u16);
 impl VariableR {
     pub fn bits(&self) -> u16 {
         self.0
@@ -107,7 +80,7 @@ impl VariableR {
 /// field should be set as described in “Table 2.2 SubPID Types in the
 /// reference document ENGINEERING CHANGE NOTICE, USB 2.0 Link Power
 /// Management Addendum”.
-pub(crate) struct SubPIDR(u8);
+pub struct SubPIDR(u8);
 impl SubPIDR {
     pub fn bits(&self) -> u8 {
         self.0
@@ -115,12 +88,6 @@ impl SubPIDR {
 }
 
 impl W {
-    /// Write raw bits.
-    pub unsafe fn bits(&mut self, v: u16) -> &mut Self {
-        self.bits = v;
-        self
-    }
-
     pub fn variable(&mut self) -> VariableW {
         VariableW { w: self }
     }
@@ -129,7 +96,7 @@ impl W {
     }
 }
 
-pub(crate) struct VariableW<'a> {
+pub struct VariableW<'a> {
     w: &'a mut W,
 }
 impl<'a> VariableW<'a> {
@@ -142,7 +109,7 @@ impl<'a> VariableW<'a> {
     }
 }
 
-pub(crate) struct SubPIDW<'a> {
+pub struct SubPIDW<'a> {
     w: &'a mut W,
 }
 impl<'a> SubPIDW<'a> {
diff --git a/src/pipe/pck_size.rs b/src/pipe/pck_size.rs
index 48441a8..f257522 100644
--- a/src/pipe/pck_size.rs
+++ b/src/pipe/pck_size.rs
@@ -1,58 +1,22 @@
+use super::register::{Readable, Register, Writable, R as GenR, W as GenW};
+
 /// § 32.8.7.3
 /// Packet Size.
 ///
 /// Offset: 0x04 & 0x14
 /// Reset: 0xxxxxxxxx
 /// Property: NA
-#[derive(Clone, Copy, Debug)]
-#[repr(C, packed)]
-pub(crate) struct PckSize(u32);
-
-pub(crate) struct R {
-    bits: u32,
-}
-
-pub(crate) struct W {
-    bits: u32,
-}
-
-impl PckSize {
-    pub fn read(self) -> R {
-        R { bits: self.0 }
-    }
 
-    pub fn write<F>(&mut self, f: F)
-    where
-        F: FnOnce(&mut W) -> &mut W,
-    {
-        let mut w = W { bits: self.0 };
-        f(&mut w);
-        self.0 = w.bits;
-    }
+pub type PckSize = Register<u32, _PckSize>;
+impl Readable for PckSize {}
+impl Writable for PckSize {}
 
-    pub fn modify<F>(&mut self, f: F)
-    where
-        for<'w> F: FnOnce(&R, &'w mut W) -> &'w mut W,
-    {
-        let r = R { bits: self.0 };
-        let mut w = W { bits: self.0 };
-        f(&r, &mut w);
-        self.0 = w.bits;
-    }
-}
+pub type R = GenR<u32, PckSize>;
+pub type W = GenW<u32, PckSize>;
 
-impl From<u32> for PckSize {
-    fn from(v: u32) -> Self {
-        Self(v)
-    }
-}
+pub struct _PckSize;
 
 impl R {
-    /// Value in raw bits.
-    pub fn bits(&self) -> u32 {
-        self.bits
-    }
-
     pub fn auto_zlp(&self) -> AutoZLPR {
         let bits = {
             const POS: u8 = 31;
@@ -104,7 +68,7 @@ impl R {
 /// When enabled, the USB module will manage the ZLP handshake by
 /// hardware. This bit is for OUT pipes only. When disabled the
 /// handshake should be managed by firmware.
-pub(crate) struct AutoZLPR(bool);
+pub struct AutoZLPR(bool);
 impl AutoZLPR {
     pub fn bit(&self) -> bool {
         self.0
@@ -125,7 +89,7 @@ impl AutoZLPR {
 ///
 /// These bits are cleared upon sending a USB reset.
 #[derive(Clone, Copy, Debug, PartialEq)]
-pub(crate) enum SizeR {
+pub enum SizeR {
     Bytes8,
     Bytes16,
     Bytes32,
@@ -204,7 +168,7 @@ impl From<u8> for SizeR {
 /// For OUT pipes, MULTI_PACKET_SIZE holds the total data size for the
 /// complete transfer. This value must be a multiple of the maximum
 /// packet size.
-pub(crate) struct MultiPacketSizeR(u16);
+pub struct MultiPacketSizeR(u16);
 impl MultiPacketSizeR {
     pub fn bits(&self) -> u16 {
         self.0
@@ -217,7 +181,7 @@ impl MultiPacketSizeR {
 /// sent in the last OUT or SETUP transaction for an OUT pipe, or of
 /// the number of bytes to be received in the next IN transaction for
 /// an input pipe.
-pub(crate) struct ByteCountR(u16);
+pub struct ByteCountR(u16);
 impl ByteCountR {
     pub fn bits(&self) -> u16 {
         self.0
@@ -225,12 +189,6 @@ impl ByteCountR {
 }
 
 impl W {
-    /// Write raw bits.
-    pub unsafe fn bits(&mut self, v: u32) -> &mut Self {
-        self.bits = v;
-        self
-    }
-
     pub fn auto_zlp(&mut self) -> AutoZLPW {
         AutoZLPW { w: self }
     }
@@ -248,7 +206,7 @@ impl W {
     }
 }
 
-pub(crate) struct AutoZLPW<'a> {
+pub struct AutoZLPW<'a> {
     w: &'a mut W,
 }
 impl<'a> AutoZLPW<'a> {
@@ -270,7 +228,7 @@ impl<'a> AutoZLPW<'a> {
 }
 
 #[derive(Copy, Clone, Debug, PartialEq)]
-pub(crate) enum SizeW {
+pub enum SizeW {
     Bytes8,
     Bytes16,
     Bytes32,
@@ -296,7 +254,7 @@ impl SizeW {
 }
 
 /// Proxy for `SizeW`
-pub(crate) struct _SizeW<'a> {
+pub struct _SizeW<'a> {
     w: &'a mut W,
 }
 impl<'a> _SizeW<'a> {
@@ -345,7 +303,7 @@ impl<'a> _SizeW<'a> {
     }
 }
 
-pub(crate) struct MultiPacketSizeW<'a> {
+pub struct MultiPacketSizeW<'a> {
     w: &'a mut W,
 }
 impl<'a> MultiPacketSizeW<'a> {
@@ -360,7 +318,7 @@ impl<'a> MultiPacketSizeW<'a> {
     }
 }
 
-pub(crate) struct ByteCountW<'a> {
+pub struct ByteCountW<'a> {
     w: &'a mut W,
 }
 impl<'a> ByteCountW<'a> {
diff --git a/src/pipe/register.rs b/src/pipe/register.rs
new file mode 100644
index 0000000..555b70a
--- /dev/null
+++ b/src/pipe/register.rs
@@ -0,0 +1,95 @@
+//! Generic register access.
+
+use core::marker::PhantomData;
+use vcell::VolatileCell;
+
+pub trait Readable {}
+pub trait Writable {}
+
+pub struct Register<T, Reg> {
+    value: VolatileCell<T>,
+    _marker: PhantomData<Reg>,
+}
+
+impl<T, Reg> From<T> for Register<T, Reg> {
+    fn from(v: T) -> Self {
+        Self {
+            value: VolatileCell::new(v),
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl<T, Reg> Register<T, Reg>
+where
+    Self: Readable,
+    T: Copy,
+{
+    pub fn read(&self) -> R<T, Self> {
+        R {
+            bits: self.value.get(),
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl<T, Reg> Register<T, Reg>
+where
+    Self: Readable + Writable,
+    T: Copy,
+{
+    pub fn write<F>(&self, f: F)
+    where
+        F: FnOnce(&mut W<T, Self>) -> &mut W<T, Self>,
+    {
+        let mut w = W {
+            bits: self.value.get(),
+            _marker: PhantomData,
+        };
+        self.value.set(f(&mut w).bits);
+    }
+
+    pub fn modify<F>(&self, f: F)
+    where
+        F: FnOnce(T, &mut W<T, Self>) -> &mut W<T, Self>,
+    {
+        let mut w = W {
+            bits: self.value.get(),
+            _marker: PhantomData,
+        };
+        self.value.set(f(w.bits, &mut w).bits);
+    }
+}
+
+pub struct R<T, Reg> {
+    pub bits: T,
+    _marker: PhantomData<Reg>,
+}
+
+impl<T, Reg> R<T, Reg>
+where
+    T: Copy,
+{
+    pub fn new(bits: T) -> Self {
+        Self {
+            bits,
+            _marker: PhantomData,
+        }
+    }
+
+    pub fn bits(&self) -> T {
+        self.bits
+    }
+}
+
+pub struct W<T, Reg> {
+    pub bits: T,
+    _marker: PhantomData<Reg>,
+}
+
+impl<T, Reg> W<T, Reg> {
+    pub unsafe fn bits(&mut self, bits: T) -> &mut Self {
+        self.bits = bits;
+        self
+    }
+}
diff --git a/src/pipe/status_bk.rs b/src/pipe/status_bk.rs
index 50a549c..892da96 100644
--- a/src/pipe/status_bk.rs
+++ b/src/pipe/status_bk.rs
@@ -1,48 +1,22 @@
+use super::register::{Readable, Register, Writable, R as GenR, W as GenW};
+
 /// §32.8.7.5
 /// Host Status Bank.
 ///
 /// Offset: 0x0a & 0x1a
 /// Reset: 0xxxxxxx
 /// Property: NA
-#[derive(Clone, Copy, Debug)]
-#[repr(C, packed)]
-pub(crate) struct StatusBk(u8);
-
-pub(crate) struct R {
-    bits: u8,
-}
 
-pub(crate) struct W {
-    bits: u8,
-}
+pub type StatusBk = Register<u8, _StatusBk>;
+impl Readable for StatusBk {}
+impl Writable for StatusBk {}
 
-impl StatusBk {
-    pub fn read(self) -> R {
-        R { bits: self.0 }
-    }
-
-    pub fn write<F>(&mut self, f: F)
-    where
-        F: FnOnce(&mut W) -> &mut W,
-    {
-        let mut w = W { bits: self.0 };
-        f(&mut w);
-        self.0 = w.bits;
-    }
-}
+pub type R = GenR<u8, StatusBk>;
+pub type W = GenW<u8, StatusBk>;
 
-impl From<u8> for StatusBk {
-    fn from(v: u8) -> Self {
-        Self(v)
-    }
-}
+pub struct _StatusBk;
 
 impl R {
-    /// Value in raw bits.
-    pub fn bits(&self) -> u8 {
-        self.bits
-    }
-
     pub fn errorflow(&self) -> ErrorFlowR {
         let bits = {
             const POS: u8 = 1;
@@ -75,7 +49,7 @@ impl R {
 /// transfer, a NAK handshake has been received. For Isochronous IN
 /// transfer, an overrun condition has occurred. For Isochronous OUT
 /// transfer, an underflow condition has occurred.
-pub(crate) struct ErrorFlowR(bool);
+pub struct ErrorFlowR(bool);
 impl ErrorFlowR {
     pub fn bit(&self) -> bool {
         self.0
@@ -96,7 +70,7 @@ impl ErrorFlowR {
 ///
 /// This bit is set when a CRC error has been detected in an
 /// isochronous IN endpoint bank.
-pub(crate) struct CRCErrR(bool);
+pub struct CRCErrR(bool);
 impl CRCErrR {
     pub fn bit(&self) -> bool {
         self.0
@@ -112,12 +86,6 @@ impl CRCErrR {
 }
 
 impl W {
-    /// Write raw bits.
-    pub unsafe fn bits(&mut self, v: u8) -> &mut Self {
-        self.bits = v;
-        self
-    }
-
     pub fn errorflow(&mut self) -> ErrorFlowW {
         ErrorFlowW { w: self }
     }
@@ -127,7 +95,7 @@ impl W {
     }
 }
 
-pub(crate) struct ErrorFlowW<'a> {
+pub struct ErrorFlowW<'a> {
     w: &'a mut W,
 }
 impl<'a> ErrorFlowW<'a> {
@@ -148,7 +116,7 @@ impl<'a> ErrorFlowW<'a> {
     }
 }
 
-pub(crate) struct CRCErrW<'a> {
+pub struct CRCErrW<'a> {
     w: &'a mut W,
 }
 impl<'a> CRCErrW<'a> {
diff --git a/src/pipe/status_pipe.rs b/src/pipe/status_pipe.rs
index d7db9c6..9bd1e32 100644
--- a/src/pipe/status_pipe.rs
+++ b/src/pipe/status_pipe.rs
@@ -1,46 +1,20 @@
+use super::register::{Readable, Register, Writable, R as GenR, W as GenW};
+
 /// Host Status Pipe.
 ///
 /// Offset: 0x0e & 0x1e
 /// Reset: 0xxxxxx
 /// Property: PAC Write-Protection, Write-Synchronized, Read-Synchronized
-#[derive(Clone, Copy, Debug)]
-#[repr(C, packed)]
-pub(crate) struct StatusPipe(u8);
-
-pub(crate) struct R {
-    bits: u8,
-}
-pub(crate) struct W {
-    bits: u8,
-}
 
-impl StatusPipe {
-    pub fn read(self) -> R {
-        R { bits: self.0 }
-    }
+pub type StatusPipe = Register<u8, _StatusPipe>;
+impl Readable for StatusPipe {}
+impl Writable for StatusPipe {}
 
-    pub fn write<F>(&mut self, f: F)
-    where
-        F: FnOnce(&mut W) -> &mut W,
-    {
-        let mut w = W { bits: self.0 };
-        f(&mut w);
-        self.0 = w.bits;
-    }
-}
-
-impl From<u8> for StatusPipe {
-    fn from(v: u8) -> Self {
-        Self(v)
-    }
-}
+pub type R = GenR<u8, StatusPipe>;
+pub type W = GenW<u8, StatusPipe>;
 
+pub struct _StatusPipe;
 impl R {
-    /// Value in raw bits.
-    pub fn bits(&self) -> u8 {
-        self.bits
-    }
-
     pub fn ercnt(&self) -> ErCntR {
         let bits = {
             const POS: u8 = 5;
@@ -109,7 +83,7 @@ impl R {
 /// Pipe Error Counter
 ///
 /// The number of errors detected on the pipe.
-pub(crate) struct ErCntR(u8);
+pub struct ErCntR(u8);
 impl ErCntR {
     pub fn bits(&self) -> u8 {
         self.0
@@ -122,7 +96,7 @@ impl ErCntR {
 ///
 /// This bit is set when a CRC 16 error has been detected during a IN
 /// transactions.
-pub(crate) struct CRC16ErR(bool);
+pub struct CRC16ErR(bool);
 impl CRC16ErR {
     pub fn bit(&self) -> bool {
         self.0
@@ -143,7 +117,7 @@ impl CRC16ErR {
 ///
 /// This bit is set when a Time Out error has been detected during a
 /// USB transaction.
-pub(crate) struct TOutErrR(bool);
+pub struct TOutErrR(bool);
 impl TOutErrR {
     pub fn bit(&self) -> bool {
         self.0
@@ -164,7 +138,7 @@ impl TOutErrR {
 ///
 /// This bit is set when a PID error has been detected during a USB
 /// transaction.
-pub(crate) struct PIDErR(bool);
+pub struct PIDErR(bool);
 impl PIDErR {
     pub fn bit(&self) -> bool {
         self.0
@@ -185,7 +159,7 @@ impl PIDErR {
 ///
 /// This bit is set when a Data PID error has been detected during a
 /// USB transaction.
-pub(crate) struct DaPIDErR(bool);
+pub struct DaPIDErR(bool);
 impl DaPIDErR {
     pub fn bit(&self) -> bool {
         self.0
@@ -205,7 +179,7 @@ impl DaPIDErR {
 /// This bit defines the Data Toggle Error Status.
 ///
 /// This bit is set when a Data Toggle Error has been detected.
-pub(crate) struct DTglErR(bool);
+pub struct DTglErR(bool);
 impl DTglErR {
     pub fn bit(&self) -> bool {
         self.0
@@ -221,12 +195,6 @@ impl DTglErR {
 }
 
 impl W {
-    /// Write raw bits.
-    pub unsafe fn bits(&mut self, v: u8) -> &mut Self {
-        self.bits = v;
-        self
-    }
-
     pub fn ercnt(&mut self) -> ErCntW {
         ErCntW { w: self }
     }
@@ -255,7 +223,7 @@ impl W {
 /// Pipe Error Counter
 ///
 /// The number of errors detected on the pipe.
-pub(crate) struct ErCntW<'a> {
+pub struct ErCntW<'a> {
     w: &'a mut W,
 }
 impl<'a> ErCntW<'a> {
@@ -278,7 +246,7 @@ impl<'a> ErCntW<'a> {
 ///
 /// This bit is set when a CRC 16 error has been detected during a IN
 /// transactions.
-pub(crate) struct CRC16ErW<'a> {
+pub struct CRC16ErW<'a> {
     w: &'a mut W,
 }
 impl<'a> CRC16ErW<'a> {
@@ -305,7 +273,7 @@ impl<'a> CRC16ErW<'a> {
 ///
 /// This bit is set when a Time Out error has been detected during a
 /// USB transaction.
-pub(crate) struct TOutErW<'a> {
+pub struct TOutErW<'a> {
     w: &'a mut W,
 }
 impl<'a> TOutErW<'a> {
@@ -332,7 +300,7 @@ impl<'a> TOutErW<'a> {
 ///
 /// This bit is set when a PID error has been detected during a USB
 /// transaction.
-pub(crate) struct PIDErW<'a> {
+pub struct PIDErW<'a> {
     w: &'a mut W,
 }
 impl<'a> PIDErW<'a> {
@@ -359,7 +327,7 @@ impl<'a> PIDErW<'a> {
 ///
 /// This bit is set when a Data PID error has been detected during a
 /// USB transaction.
-pub(crate) struct DaPIDErW<'a> {
+pub struct DaPIDErW<'a> {
     w: &'a mut W,
 }
 impl<'a> DaPIDErW<'a> {
@@ -385,7 +353,7 @@ impl<'a> DaPIDErW<'a> {
 /// This bit defines the Data Toggle Error Status.
 ///
 /// This bit is set when a Data Toggle Error has been detected.
-pub(crate) struct DTglErW<'a> {
+pub struct DTglErW<'a> {
     w: &'a mut W,
 }
 impl<'a> DTglErW<'a> {