From 95dbf4f4f2d12560feff59f057911fc96ba2ab23 Mon Sep 17 00:00:00 2001
From: Matthew Leach <dev@mattleach.net>
Date: Wed, 25 Feb 2026 20:30:07 +0000
Subject: [PATCH] drviers: chrdev: random: new

Add a new chardev which implements /dev/random.
---
 src/drivers/chrdev/mod.rs        |  3 ++
 src/drivers/{ => chrdev}/null.rs |  0
 src/drivers/chrdev/random.rs     | 90 ++++++++++++++++++++++++++++++++
 src/drivers/{ => chrdev}/zero.rs |  0
 src/drivers/mod.rs               |  4 +-
 5 files changed, 95 insertions(+), 2 deletions(-)
 create mode 100644 src/drivers/chrdev/mod.rs
 rename src/drivers/{ => chrdev}/null.rs (100%)
 create mode 100644 src/drivers/chrdev/random.rs
 rename src/drivers/{ => chrdev}/zero.rs (100%)

diff --git a/src/drivers/chrdev/mod.rs b/src/drivers/chrdev/mod.rs
new file mode 100644
index 0000000..b355282
--- /dev/null
+++ b/src/drivers/chrdev/mod.rs
@@ -0,0 +1,3 @@
+pub mod null;
+pub mod random;
+pub mod zero;
diff --git a/src/drivers/null.rs b/src/drivers/chrdev/null.rs
similarity index 100%
rename from src/drivers/null.rs
rename to src/drivers/chrdev/null.rs
diff --git a/src/drivers/chrdev/random.rs b/src/drivers/chrdev/random.rs
new file mode 100644
index 0000000..0474f90
--- /dev/null
+++ b/src/drivers/chrdev/random.rs
@@ -0,0 +1,90 @@
+use crate::{
+    drivers::{
+        CharDriver, DriverManager, OpenableDevice, ReservedMajors, fs::dev::devfs,
+        init::PlatformBus,
+    },
+    fs::{
+        fops::FileOps,
+        open_file::{FileCtx, OpenFile},
+    },
+    kernel::rand::sys_getrandom,
+    kernel_driver,
+};
+use alloc::{boxed::Box, string::ToString, sync::Arc};
+use async_trait::async_trait;
+use core::{future::Future, pin::Pin};
+use libkernel::{
+    driver::CharDevDescriptor,
+    error::Result,
+    fs::{OpenFlags, attr::FilePermissions},
+    memory::address::UA,
+};
+
+struct RandomFileOps;
+
+#[async_trait]
+impl FileOps for RandomFileOps {
+    async fn read(&mut self, _ctx: &mut FileCtx, buf: UA, count: usize) -> Result<usize> {
+        self.readat(buf, count, 0).await
+    }
+
+    async fn writeat(&mut self, _buf: UA, count: usize, _offset: u64) -> Result<usize> {
+        // Just consume the write.
+        Ok(count)
+    }
+
+    async fn readat(&mut self, buf: UA, count: usize, _offset: u64) -> Result<usize> {
+        sys_getrandom(buf.cast(), count as _, 0).await
+    }
+
+    fn poll_read_ready(&self) -> Pin<Box<dyn Future<Output = Result<()>> + Send>> {
+        Box::pin(async { Ok(()) })
+    }
+}
+
+struct RandomDev;
+
+impl OpenableDevice for RandomDev {
+    fn open(&self, flags: OpenFlags) -> Result<Arc<OpenFile>> {
+        Ok(Arc::new(OpenFile::new(Box::new(RandomFileOps), flags)))
+    }
+}
+
+struct RandomCharDev {
+    random_dev: Arc<dyn OpenableDevice>,
+}
+
+impl RandomCharDev {
+    fn new() -> Result<Self> {
+        devfs().mknod(
+            "random".to_string(),
+            CharDevDescriptor {
+                major: ReservedMajors::Random as _,
+                minor: 0,
+            },
+            FilePermissions::from_bits_retain(0o666),
+        )?;
+
+        Ok(Self {
+            random_dev: Arc::new(RandomDev),
+        })
+    }
+}
+
+impl CharDriver for RandomCharDev {
+    fn get_device(&self, minor: u64) -> Option<Arc<dyn OpenableDevice>> {
+        if minor == 0 {
+            Some(self.random_dev.clone())
+        } else {
+            None
+        }
+    }
+}
+
+/// Driver initialisation entry point invoked during kernel boot.
+pub fn random_chardev_init(_bus: &mut PlatformBus, dm: &mut DriverManager) -> Result<()> {
+    let cdev = RandomCharDev::new()?;
+    dm.register_char_driver(ReservedMajors::Random as _, Arc::new(cdev))
+}
+
+kernel_driver!(random_chardev_init);
diff --git a/src/drivers/zero.rs b/src/drivers/chrdev/zero.rs
similarity index 100%
rename from src/drivers/zero.rs
rename to src/drivers/chrdev/zero.rs
diff --git a/src/drivers/mod.rs b/src/drivers/mod.rs
index 25f3ff5..c4342db 100644
--- a/src/drivers/mod.rs
+++ b/src/drivers/mod.rs
@@ -20,20 +20,20 @@ use crate::{
     sync::SpinLock,
 };
 
+pub mod chrdev;
 pub mod fdt_prober;
 pub mod fs;
 pub mod init;
 pub mod interrupts;
-pub mod null;
 pub mod probe;
 pub mod timer;
 pub mod uart;
-pub mod zero;
 
 #[repr(u64)]
 pub enum ReservedMajors {
     Null = 1,
     Zero = 2,
+    Random = 3,
     Console = 5,
     Uart = 10,
     End = 11,