initial commit

Signed-off-by: Sean Cross <sean@xobs.io>

.gitattributes

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+*.py text eol=lf
+*.dfu binary
+*.png binary
+*.jpg binary
+*.bin binary
+*.elf binary
+*.h text eol=lf
+*.c text eol=lf
+*.s text eol=lf
+*.S text eol=lf
+README.* text eol=lf
+LICENSE text eol=lf
+Makefile text eol=lf
+*.mk text eol=lf
+*.sh text eol=lf
+*.ps1 text eol=crlf
+.gitignore text eol=lf
+.gitattributes text eol=lf

.gitignore

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+/target
+Cargo.lock

Cargo.toml

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+[package]
+name = "hardware_register"
+version = "0.1.0"
+authors = ["Sean Cross <sean@xobs.io>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

src/lib.rs

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+use std::convert::TryInto;
+pub struct Field {
+    /// A bitmask we use to AND to the value, unshifted.
+    /// E.g. for a width of `3` bits, this mask would be 0b111.
+    mask: usize,
+
+    /// Offset of the first bit in this field
+    offset: usize,
+}
+
+impl Field {
+    /// Define a new CSR field with the given width at a specified
+    /// offset from the start of the register.
+    pub const fn new(width: usize, offset: usize) -> Field {
+        // assert!(width != 0, "field width cannot be 0");
+        // assert!((width + offset) < 32, "field with and offset must fit within a 32-bit value");
+
+        // It would be lovely if we could call `usize::pow()` in a const fn.
+        let mask = match width {
+            0 => 0,
+            1 => 1,
+            2 => 3,
+            3 => 7,
+            4 => 15,
+            5 => 31,
+            6 => 63,
+            7 => 127,
+            8 => 255,
+            9 => 511,
+            10 => 1023,
+            11 => 2047,
+            12 => 4095,
+            13 => 8191,
+            14 => 16383,
+            15 => 32767,
+            16 => 65535,
+            17 => 131071,
+            18 => 262143,
+            19 => 524287,
+            20 => 1048575,
+            21 => 2097151,
+            22 => 4194303,
+            23 => 8388607,
+            24 => 16777215,
+            25 => 33554431,
+            26 => 67108863,
+            27 => 134217727,
+            28 => 268435455,
+            29 => 536870911,
+            30 => 1073741823,
+            31 => 2147483647,
+            _ => 0,
+        };
+        Field { mask, offset }
+    }
+}
+
+pub struct CSR<T> {
+    base: *mut T,
+}
+
+impl<T> CSR<T>
+where
+    T: std::convert::TryFrom<usize> + std::convert::TryInto<usize> + std::default::Default,
+{
+    pub fn new(base: *mut T) -> Self {
+        CSR { base }
+    }
+    pub fn r(&mut self, reg: usize, field: Field) -> T {
+        let usize_base: *mut usize = unsafe { core::mem::transmute(&self.base) };
+        ((unsafe { usize_base.add(reg).read_volatile() } >> field.offset) & field.mask)
+            .try_into()
+            .unwrap_or_default()
+    }
+    pub fn rw(&mut self, reg: usize, field: Field, value: T) {
+        let usize_base: *mut usize = unsafe { core::mem::transmute(&self.base) };
+        let value_as_usize: usize = value.try_into().unwrap_or_default() << field.offset;
+        let previous = unsafe { usize_base.add(reg).read_volatile() } & ! field.mask;
+        unsafe { usize_base.add(reg).write_volatile(previous | value_as_usize)};
+    }
+    pub fn ow(&mut self, reg: usize, field: Field, value: T) {
+        let usize_base: *mut usize = unsafe { core::mem::transmute(&self.base) };
+        let value_as_usize: usize = value.try_into().unwrap_or_default() << field.offset;
+        unsafe { usize_base.add(reg).write_volatile(value_as_usize)};
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    pub mod pac {
+        pub mod audio {
+            pub const RX_CTL: usize = 0x0c;
+            pub const RX_CTL_ENABLE: crate::Field = crate::Field::new(1, 0);
+            pub const RX_CTL_RESET: crate::Field = crate::Field::new(1, 1);
+        }
+        pub mod uart {
+            pub const RXTX: usize = 0x00;
+            pub const RXTX_RXTX: crate::Field = crate::Field::new(8, 0);
+            pub const TXFULL: usize = 0x04;
+            pub const TXFULL_TXFULL: crate::Field = crate::Field::new(1, 0);
+        }
+    }
+    #[test]
+    fn compile_check() {
+        use super::*;
+        let mut audio = CSR::new(0x1000_0000 as *mut u32);
+        audio.r(pac::audio::RX_CTL, pac::audio::RX_CTL_ENABLE);
+        audio.rw(pac::audio::RX_CTL, pac::audio::RX_CTL_RESET, 1);
+
+        let mut uart = CSR::new(0x1001_0000 as *mut u8);
+        uart.ow(pac::uart::RXTX, pac::uart::RXTX_RXTX, b'a');
+        assert_ne!(uart.r(pac::uart::TXFULL, pac::uart::TXFULL_TXFULL), 1);
+
+        // Note: These also still compile.
+        uart.ow(pac::uart::RXTX, pac::uart::TXFULL_TXFULL, b'a');
+
+        // This compiles but requires a cast since `audio` is a pointer to
+        // u32, whereas `uart` is a pointer to u8.
+        audio.ow(pac::uart::RXTX, pac::uart::RXTX_RXTX, b'a' as _);
+    }
+}