From a29698221dd9ad5d33d826aacc312acf97f0509f Mon Sep 17 00:00:00 2001
From: Stephen Marz <stephen.marz@utk.edu>
Date: Tue, 10 Mar 2020 17:16:57 -0400
Subject: [PATCH] Added virtio structures and stubs for setting up devices

---
 risc_v/ch9/src/virtio.rs | 158 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 158 insertions(+)
 create mode 100755 risc_v/ch9/src/virtio.rs

diff --git a/risc_v/ch9/src/virtio.rs b/risc_v/ch9/src/virtio.rs
new file mode 100755
index 0000000..b397b38
--- /dev/null
+++ b/risc_v/ch9/src/virtio.rs
@@ -0,0 +1,158 @@
+// virtio.rs
+// VirtIO routines for the VirtIO protocol
+// Stephen Marz
+// 10 March 2020
+
+// Flags
+// Descriptor flags have VIRTIO_DESC_F as a prefix
+// Available flags have VIRTIO_AVAIL_F
+
+pub const VIRTIO_DESC_F_NEXT: u16 = 1;
+pub const VIRTIO_DESC_F_WRITE: u16 = 2;
+pub const VIRTIO_DESC_F_INDIRECT: u16 = 4;
+
+pub const VIRTIO_AVAIL_F_NO_INTERRUPT: u16 = 1;
+
+pub const VIRTIO_USED_F_NO_NOTIFY: u16 = 1;
+
+// VirtIO structures
+#[repr(C)]
+pub struct Descriptor {
+    addr: u64,
+    len: u32,
+    flags: u16,
+    next: u16,
+}
+
+#[repr(C)]
+pub struct Available {
+    flags: u16,
+    idx: u16,
+    ring: [u16; 1024],
+    event: u16,
+}
+
+#[repr(C)]
+pub struct UsedElem {
+    id: u32,
+    len: u32,
+}
+
+#[repr(C)]
+pub struct Used {
+    flags: u16,
+    idx: u16,
+    ring: [UsedElem; 1024],
+    event: u16,
+}
+
+// We probably shouldn't put these here, but it'll help
+// with probing the bus, etc. These are architecture specific
+// which is why I say that.
+pub const MMIO_VIRTIO_START: usize  = 0x1000_1000;
+pub const MMIO_VIRTIO_END: usize    = 0x1000_8000;
+pub const MMIO_VIRTIO_STRIDE: usize = 0x1000;
+
+/// Probe the VirtIO bus for devices that might be
+/// out there.
+pub fn probe() {
+    // Rust's for loop uses an Iterator object, which now has a step_by modifier
+    // to change how much it steps. Also recall that ..= means up to AND including
+    // MMIO_VIRTIO_END.
+    for addr in (MMIO_VIRTIO_START..=MMIO_VIRTIO_END).step_by(MMIO_VIRTIO_STRIDE) {
+        print!("Virtio probing 0x{:08x}...", addr);
+        unsafe {
+            let ptr = addr as *mut u32;
+            // 0x74_72_69_76 is "virt" in little endian, so in reality
+            // it is triv. All VirtIO devices have this attached to the
+            // MagicValue register (offset 0x000)
+            if 0x74_72_69_76 != ptr.read_volatile() {
+                println!("not virtio.");
+            }
+            // If we are a virtio device, we now need to see if anything
+            // is actually attached to it. The DeviceID register will
+            // contain what type of device this is. If this value is 0,
+            // then it is not connected.
+            else if 0 == ptr.add(2).read_volatile() {
+                println!("not connected.");
+            }
+            else {
+                match ptr.add(2).read_volatile() {
+                    // DeviceID 1 is a network device
+                    1 => {
+                        print!("network device...");
+                        if false == setup_network_device(ptr) {
+                            println!("setup failed.");
+                        }
+                        else {
+                            println!("setup succeeded!");
+                        }
+                    },
+                    // DeviceID 2 is a block device
+                    2 => {
+                        print!("block device...");
+                        if false == setup_block_device(ptr) {
+                            println!("setup failed.");
+                        }
+                        else {
+                            println!("setup succeeded!");
+                        }
+                    },
+                    // DeviceID 4 is a random number generator device
+                    4 => {
+                        print!("entropy device...");
+                        if false == setup_entropy_device(ptr) {
+                            println!("setup failed.");
+                        }
+                        else {
+                            println!("setup succeeded!");
+                        }
+                    },
+                    // DeviceID 16 is a GPU device
+                    16 => {
+                        print!("GPU device...");
+                        if false == setup_gpu_device(ptr) {
+                            println!("setup failed.");
+                        }
+                        else {
+                            println!("setup succeeded!");
+                        }
+                    },
+                    // DeviceID 18 is an input device
+                    18 => {
+                        print!("input device...");
+                        if false == setup_input_device(ptr) {
+                            println!("setup failed.");
+                        }
+                        else {
+                            println!("setup succeeded!");
+                        }
+                    },
+                    _ => {
+                        println!("unknown device type.")
+                    }
+                }
+            }
+        }
+    }
+}
+
+pub fn setup_block_device(ptr: *mut u32) -> bool {
+    false
+}
+
+pub fn setup_entropy_device(ptr: *mut u32) -> bool {
+    false
+}
+
+pub fn setup_network_device(ptr: *mut u32) -> bool {
+    false
+}
+
+pub fn setup_gpu_device(ptr: *mut u32) -> bool {
+    false
+}
+
+pub fn setup_input_device(ptr: *mut u32) -> bool {
+    false
+}