From c7e5123f6604fbb9ca510f01af9b60e777bf57b4 Mon Sep 17 00:00:00 2001
From: Ian McIntyre <ianpmcintyre@gmail.com>
Date: Sun, 22 Oct 2023 18:23:56 -0400
Subject: First commit

A prototype of an i.MX RT ENET driver. There's design decisions I'm
thinking of changing. Nevertheless, the smoltcp support seems to be
working; an 1170EVK can act as a DHCP client and a TCP loopback server.
---
 src/bd/rxbd.rs | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)
 create mode 100644 src/bd/rxbd.rs

(limited to 'src/bd/rxbd.rs')

diff --git a/src/bd/rxbd.rs b/src/bd/rxbd.rs
new file mode 100644
index 0000000..8523d6e
--- /dev/null
+++ b/src/bd/rxbd.rs
@@ -0,0 +1,95 @@
+//! Enhanced receive buffer descriptor layout and fields.
+
+use ral_registers::{RORegister, RWRegister};
+
+#[repr(C)]
+pub struct RxBD {
+    pub data_length: RORegister<u16>,
+    pub flags: RWRegister<u16>,
+    pub data_buffer_pointer: RWRegister<u32>,
+    pub status: RWRegister<u16>,
+    pub control: RWRegister<u16>,
+    pub checksum: RORegister<u16>,
+    pub header: RORegister<u16>,
+    _reserved0: [u16; 1],
+    pub last_bdu: RWRegister<u16>,
+    pub timestamp_1588: RORegister<u32>,
+    _reserved1: [u16; 4],
+}
+
+bdfields!(flags, u16,
+    empty               [ offset = 15, bits = 1, ],
+    ro1                 [ offset = 14, bits = 1, ],
+    wrap                [ offset = 13, bits = 1, ],
+    ro2                 [ offset = 12, bits = 1, ],
+    last                [ offset = 11, bits = 1, ],
+
+    miss                [ offset =  8, bits = 1, ],
+    broadcast           [ offset =  7, bits = 1, ],
+    multicast           [ offset =  6, bits = 1, ],
+    length_violation    [ offset =  5, bits = 1, ],
+    non_octet_violation [ offset =  4, bits = 1, ],
+
+    crc_error           [ offset =  2, bits = 1, ],
+    overrun             [ offset =  1, bits = 1, ],
+    truncated           [ offset =  0, bits = 1, ],
+);
+
+bdfields!(status, u16,
+    vlan_priority           [ offset = 13, bits = 3, ],
+    ip_checksum_error       [ offset =  5, bits = 1, ],
+    protocol_checksum_error [ offset =  4, bits = 1, ],
+    vlan                    [ offset =  2, bits = 1, ],
+    ipv6                    [ offset =  1, bits = 1, ],
+    frag                    [ offset =  0, bits = 1, ],
+);
+
+bdfields!(control, u16,
+    mac_error               [ offset = 15, bits = 1, ],
+    phy_error               [ offset = 10, bits = 1, ],
+    collision               [ offset =  9, bits = 1, ],
+    unicast                 [ offset =  8, bits = 1, ],
+    interrupt               [ offset =  7, bits = 1, ],
+);
+
+bdfields!(header, u16,
+    length      [ offset = 11, bits = 5, ],
+    protocol    [ offset =  0, bits = 8, ],
+);
+
+bdfields!(last_bdu, u16,
+    last_bdu    [ offset = 15, bits = 1, ],
+);
+
+#[cfg(test)]
+mod tests {
+    use core::ptr::addr_of;
+
+    use super::RxBD;
+
+    fn zeroed() -> RxBD {
+        // Safety: zero bitpattern is fine for primitive fields.
+        unsafe { core::mem::MaybeUninit::zeroed().assume_init() }
+    }
+
+    #[test]
+    fn field_offsets() {
+        let rxbd = zeroed();
+        let start = &rxbd as *const _ as *const u8;
+        assert_eq!(unsafe { start.add(0x0) }, addr_of!(rxbd.data_length).cast());
+        assert_eq!(unsafe { start.add(0x2) }, addr_of!(rxbd.flags).cast());
+        assert_eq!(
+            unsafe { start.add(0x4) },
+            addr_of!(rxbd.data_buffer_pointer).cast()
+        );
+        assert_eq!(unsafe { start.add(0x8) }, addr_of!(rxbd.status).cast());
+        assert_eq!(unsafe { start.add(0xA) }, addr_of!(rxbd.control).cast());
+        assert_eq!(unsafe { start.add(0xC) }, addr_of!(rxbd.checksum).cast());
+        assert_eq!(unsafe { start.add(0xE) }, addr_of!(rxbd.header).cast());
+        assert_eq!(unsafe { start.add(0x12) }, addr_of!(rxbd.last_bdu).cast());
+        assert_eq!(
+            unsafe { start.add(0x14) },
+            addr_of!(rxbd.timestamp_1588).cast()
+        );
+    }
+}
-- 
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