nic_queues/
lib.rs

1#![no_std]
2
3pub trait RxDescriptor: Copy {
4    /// Sets buffer addr.
5    fn set_buffer_addr(&mut self, phys: u64);
6    /// Returns whether done.
7    fn is_done(&self) -> bool;
8    /// Performs the packet length operation.
9    fn packet_length(&self) -> u16;
10    /// Performs the clear status operation.
11    fn clear_status(&mut self);
12}
13
14pub trait TxDescriptor: Copy {
15    /// Sets buffer.
16    fn set_buffer(&mut self, phys: u64, len: u16);
17    /// Sets eop ifcs rs.
18    fn set_eop_ifcs_rs(&mut self);
19    /// Returns whether done.
20    fn is_done(&self) -> bool;
21    /// Performs the clear operation.
22    fn clear(&mut self);
23}
24
25pub struct RxRing<D: RxDescriptor> {
26    descs: *mut D,
27    count: usize,
28    tail: usize,
29}
30
31// SAFETY: RxRing only contains a raw pointer to a descriptor ring and plain
32// indices. Sending it to another thread is safe as long as external code
33// upholds exclusive mutation/aliasing rules for the underlying ring memory.
34unsafe impl<D: RxDescriptor> Send for RxRing<D> {}
35
36impl<D: RxDescriptor> RxRing<D> {
37    /// # Safety
38    /// `descs` must point to `count` valid, zero-initialised descriptors.
39    pub unsafe fn new(descs: *mut D, count: usize) -> Self {
40        Self {
41            descs,
42            count,
43            tail: count - 1,
44        }
45    }
46
47    /// Performs the count operation.
48    pub fn count(&self) -> usize {
49        self.count
50    }
51
52    /// Performs the tail operation.
53    pub fn tail(&self) -> usize {
54        self.tail
55    }
56
57    /// Performs the desc mut operation.
58    pub fn desc_mut(&mut self, idx: usize) -> &mut D {
59        // SAFETY: `new` guarantees `descs` points to `count` valid descriptors.
60        // Indexing is wrapped modulo `count`, so pointer arithmetic stays in ring bounds.
61        unsafe { &mut *self.descs.add(idx % self.count) }
62    }
63
64    /// Check the next descriptor; returns `(index, packet_length)` if ready.
65    pub fn poll(&self) -> Option<(usize, u16)> {
66        let next = (self.tail + 1) % self.count;
67        // SAFETY: `next < count` and `descs` points to `count` valid descriptors.
68        // Immutable access does not violate aliasing.
69        let desc = unsafe { &*self.descs.add(next) };
70        if desc.is_done() {
71            Some((next, desc.packet_length()))
72        } else {
73            None
74        }
75    }
76
77    /// Advance tail after consuming a packet. Returns new tail.
78    pub fn advance(&mut self) -> usize {
79        self.tail = (self.tail + 1) % self.count;
80        self.tail
81    }
82
83    /// Set up one RX descriptor with a pre-allocated buffer.
84    pub fn setup_desc(&mut self, idx: usize, buf_phys: u64) {
85        let d = self.desc_mut(idx);
86        d.clear_status();
87        d.set_buffer_addr(buf_phys);
88    }
89}
90
91pub struct TxRing<D: TxDescriptor> {
92    descs: *mut D,
93    count: usize,
94    tail: usize,
95}
96
97// SAFETY: TxRing stores a raw descriptor pointer and indices only. Transfer
98// across threads is sound when callers synchronize ownership of descriptor memory.
99unsafe impl<D: TxDescriptor> Send for TxRing<D> {}
100
101impl<D: TxDescriptor> TxRing<D> {
102    /// # Safety
103    /// `descs` must point to `count` valid, zero-initialised descriptors.
104    pub unsafe fn new(descs: *mut D, count: usize) -> Self {
105        Self {
106            descs,
107            count,
108            tail: 0,
109        }
110    }
111
112    /// Performs the count operation.
113    pub fn count(&self) -> usize {
114        self.count
115    }
116
117    /// Performs the tail operation.
118    pub fn tail(&self) -> usize {
119        self.tail
120    }
121
122    /// Performs the desc operation.
123    pub fn desc(&self, idx: usize) -> &D {
124        // SAFETY: `idx % count` is in bounds and `descs` points to `count` valid descriptors.
125        unsafe { &*self.descs.add(idx % self.count) }
126    }
127
128    /// Performs the desc mut operation.
129    pub fn desc_mut(&mut self, idx: usize) -> &mut D {
130        // SAFETY: `idx % count` is in bounds and mutable access is gated by `&mut self`.
131        unsafe { &mut *self.descs.add(idx % self.count) }
132    }
133
134    /// Prepare and submit a packet at the current tail slot.
135    /// Returns the descriptor index used.
136    pub fn submit(&mut self, phys: u64, len: u16) -> usize {
137        let idx = self.tail;
138        let d = self.desc_mut(idx);
139        d.clear();
140        d.set_buffer(phys, len);
141        d.set_eop_ifcs_rs();
142        self.tail = (idx + 1) % self.count;
143        idx
144    }
145
146    /// Returns whether done.
147    pub fn is_done(&self, idx: usize) -> bool {
148        self.desc(idx).is_done()
149    }
150}
nic_queues/lib.rs

nic_queues/
lib.rs
