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| 1 | +// SPDX-License-Identifier: GPL-2.0 |
| 2 | + |
| 3 | +//! Broadcom BCM2835 Random Number Generator support. |
| 4 | +
|
| 5 | +#![no_std] |
| 6 | +#![feature(allocator_api, global_asm)] |
| 7 | + |
| 8 | +use alloc::{boxed::Box, sync::Arc}; |
| 9 | +use core::pin::Pin; |
| 10 | +use kernel::prelude::*; |
| 11 | +use kernel::{ |
| 12 | + cstr, |
| 13 | + file::File, |
| 14 | + file_operations::{FileOpener, FileOperations}, |
| 15 | + io_buffer::IoBufferWriter, |
| 16 | + miscdev, |
| 17 | + platform_driver::{self, PlatformDevice, PlatformDriver}, |
| 18 | + regmap::{Regmap, RegmapConfig}, |
| 19 | +}; |
| 20 | + |
| 21 | +module! { |
| 22 | + type: RngModule, |
| 23 | + name: b"bcm2835_rng_rust", |
| 24 | + author: b"Rust for Linux Contributors", |
| 25 | + description: b"BCM2835 Random Number Generator (RNG) driver", |
| 26 | + license: b"GPL v2", |
| 27 | +} |
| 28 | + |
| 29 | +struct SharedState { |
| 30 | + regmap: Regmap, |
| 31 | +} |
| 32 | + |
| 33 | +impl SharedState { |
| 34 | + fn try_new(regmap: Regmap) -> Result<Arc<Self>> { |
| 35 | + Ok(Arc::try_new(SharedState { regmap })?) |
| 36 | + } |
| 37 | +} |
| 38 | + |
| 39 | +struct RngDevice { |
| 40 | + state: Arc<SharedState>, |
| 41 | +} |
| 42 | + |
| 43 | +impl FileOpener<Arc<SharedState>> for RngDevice { |
| 44 | + fn open(state: &Arc<SharedState>) -> Result<Self::Wrapper> { |
| 45 | + Ok(Box::try_new(RngDevice { |
| 46 | + state: state.clone(), |
| 47 | + })?) |
| 48 | + } |
| 49 | +} |
| 50 | + |
| 51 | +impl FileOperations for RngDevice { |
| 52 | + kernel::declare_file_operations!(read); |
| 53 | + |
| 54 | + fn read<T: IoBufferWriter>(&self, _: &File, data: &mut T, offset: u64) -> Result<usize> { |
| 55 | + // Succeed if the caller doesn't provide a buffer or if not at the start. |
| 56 | + if data.is_empty() || offset != 0 { |
| 57 | + return Ok(0); |
| 58 | + } |
| 59 | + |
| 60 | + let regmap = &self.state.regmap; |
| 61 | + let num_words = regmap.read(RNG_STATUS)? >> 24; |
| 62 | + if num_words == 0 { |
| 63 | + return Ok(0); |
| 64 | + } |
| 65 | + data.write(®map.read(RNG_DATA)?)?; |
| 66 | + Ok(4) |
| 67 | + } |
| 68 | +} |
| 69 | + |
| 70 | +#[derive(Default)] |
| 71 | +struct RngDriver; |
| 72 | + |
| 73 | +// TODO: Issue #260 ("Use Rust type system to make Regmap API safer"). |
| 74 | + |
| 75 | +const RNG_CTRL: u32 = 0x0; |
| 76 | +const RNG_STATUS: u32 = 0x4; |
| 77 | +const RNG_DATA: u32 = 0x8; |
| 78 | + |
| 79 | +// The initial numbers generated are "less random" so will be discarded. |
| 80 | +const RNG_WARMUP_COUNT: u32 = 0x40000; |
| 81 | +// Enable rng. |
| 82 | +const RNG_RBGEN: u32 = 0x1; |
| 83 | + |
| 84 | +impl PlatformDriver for RngDriver { |
| 85 | + type DrvData = Pin<Box<miscdev::Registration<Arc<SharedState>>>>; |
| 86 | + |
| 87 | + fn probe(pdev: &mut PlatformDevice) -> Result<Self::DrvData> { |
| 88 | + // Create Regmap which maps device registers. |
| 89 | + let cfg = RegmapConfig::new(32, 32) |
| 90 | + .reg_stride(4) |
| 91 | + .max_register(RNG_DATA); |
| 92 | + let regmap = Regmap::init_mmio_platform_resource(pdev, 0, &cfg)?; |
| 93 | + // Set warm-up count & enable. |
| 94 | + regmap.write(RNG_STATUS, RNG_WARMUP_COUNT)?; |
| 95 | + regmap.write(RNG_CTRL, RNG_RBGEN)?; |
| 96 | + // Register character device so userspace can read out random data. |
| 97 | + // TODO: use a `struct hwrng` instead of a `miscdev`. |
| 98 | + let state = SharedState::try_new(regmap)?; |
| 99 | + let dev = miscdev::Registration::new_pinned::<RngDevice>(cstr!("rust_hwrng"), None, state)?; |
| 100 | + Ok(dev) |
| 101 | + } |
| 102 | +} |
| 103 | + |
| 104 | +struct RngModule { |
| 105 | + _pdev: Pin<Box<platform_driver::Registration>>, |
| 106 | +} |
| 107 | + |
| 108 | +impl KernelModule for RngModule { |
| 109 | + fn init() -> Result<Self> { |
| 110 | + let pdev = platform_driver::Registration::new_pinned::<RngDriver>( |
| 111 | + cstr!("bcm2835-rng-rust"), |
| 112 | + // TODO: this should be an optional list. |
| 113 | + // Perhaps use an enum to specify behavioural differences. |
| 114 | + cstr!("brcm,bcm2835-rng"), |
| 115 | + &THIS_MODULE, |
| 116 | + )?; |
| 117 | + |
| 118 | + Ok(RngModule { _pdev: pdev }) |
| 119 | + } |
| 120 | +} |
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