From fc36e40eeffb4fa82709aff285fba4d3ab040cc5 Mon Sep 17 00:00:00 2001
From: Andrew Walbran <qwandor@google.com>
Date: Wed, 22 Mar 2023 16:24:24 +0000
Subject: [PATCH] Make base address constants a pointer rather than a usize.

---
 src/bare-metal/aps/examples/src/main_improved.rs | 4 ++--
 src/bare-metal/aps/examples/src/main_logger.rs   | 4 ++--
 src/bare-metal/aps/examples/src/main_minimal.rs  | 2 +-
 src/bare-metal/aps/examples/src/pl011_minimal.rs | 6 ++----
 src/exercises/bare-metal/rtc/src/main.rs         | 8 ++++----
 5 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/src/bare-metal/aps/examples/src/main_improved.rs b/src/bare-metal/aps/examples/src/main_improved.rs
index 99239d90..c5a94e58 100644
--- a/src/bare-metal/aps/examples/src/main_improved.rs
+++ b/src/bare-metal/aps/examples/src/main_improved.rs
@@ -25,13 +25,13 @@ use log::error;
 use psci::system_off;
 
 /// Base address of the primary PL011 UART.
-pub const PL011_BASE_ADDRESS: usize = 0x900_0000;
+pub const PL011_BASE_ADDRESS: *mut u32 = 0x900_0000 as _;
 
 #[no_mangle]
 extern "C" fn main(x0: u64, x1: u64, x2: u64, x3: u64) {
     // Safe because `PL011_BASE_ADDRESS` is the base address of a PL011 device,
     // and nothing else accesses that address range.
-    let mut uart = unsafe { Uart::new(PL011_BASE_ADDRESS as *mut u32) };
+    let mut uart = unsafe { Uart::new(PL011_BASE_ADDRESS) };
 
     writeln!(uart, "main({:#x}, {:#x}, {:#x}, {:#x})", x0, x1, x2, x3).unwrap();
 
diff --git a/src/bare-metal/aps/examples/src/main_logger.rs b/src/bare-metal/aps/examples/src/main_logger.rs
index c14054f5..cae58365 100644
--- a/src/bare-metal/aps/examples/src/main_logger.rs
+++ b/src/bare-metal/aps/examples/src/main_logger.rs
@@ -26,13 +26,13 @@ use log::{error, info, LevelFilter};
 use psci::system_off;
 
 /// Base address of the primary PL011 UART.
-pub const PL011_BASE_ADDRESS: usize = 0x900_0000;
+pub const PL011_BASE_ADDRESS: *mut u32 = 0x900_0000 as _;
 
 #[no_mangle]
 extern "C" fn main(x0: u64, x1: u64, x2: u64, x3: u64) {
     // Safe because `PL011_BASE_ADDRESS` is the base address of a PL011 device,
     // and nothing else accesses that address range.
-    let uart = unsafe { Uart::new(PL011_BASE_ADDRESS as *mut u32) };
+    let uart = unsafe { Uart::new(PL011_BASE_ADDRESS) };
     logger::init(uart, LevelFilter::Trace).unwrap();
 
     info!("main({:#x}, {:#x}, {:#x}, {:#x})", x0, x1, x2, x3);
diff --git a/src/bare-metal/aps/examples/src/main_minimal.rs b/src/bare-metal/aps/examples/src/main_minimal.rs
index 942e2ee5..983816e1 100644
--- a/src/bare-metal/aps/examples/src/main_minimal.rs
+++ b/src/bare-metal/aps/examples/src/main_minimal.rs
@@ -25,7 +25,7 @@ use log::error;
 use psci::system_off;
 
 /// Base address of the primary PL011 UART.
-pub const PL011_BASE_ADDRESS: usize = 0x900_0000;
+pub const PL011_BASE_ADDRESS: *mut u8 = 0x900_0000 as _;
 
 #[no_mangle]
 extern "C" fn main(x0: u64, x1: u64, x2: u64, x3: u64) {
diff --git a/src/bare-metal/aps/examples/src/pl011_minimal.rs b/src/bare-metal/aps/examples/src/pl011_minimal.rs
index 485f5d95..f747e20a 100644
--- a/src/bare-metal/aps/examples/src/pl011_minimal.rs
+++ b/src/bare-metal/aps/examples/src/pl011_minimal.rs
@@ -32,10 +32,8 @@ impl Uart {
     /// The given base address must point to the 8 MMIO control registers of a
     /// PL011 device, which must be mapped into the address space of the process
     /// as device memory and not have any other aliases.
-    pub unsafe fn new(base_address: usize) -> Self {
-        Self {
-            base_address: base_address as *mut u8,
-        }
+    pub unsafe fn new(base_address: *mut u8) -> Self {
+        Self { base_address }
     }
 
     /// Writes a single byte to the UART.
diff --git a/src/exercises/bare-metal/rtc/src/main.rs b/src/exercises/bare-metal/rtc/src/main.rs
index ad40a92a..6401d504 100644
--- a/src/exercises/bare-metal/rtc/src/main.rs
+++ b/src/exercises/bare-metal/rtc/src/main.rs
@@ -31,18 +31,18 @@ use log::{error, info, LevelFilter};
 use psci::system_off;
 
 /// Base address of the primary PL011 UART.
-pub const PL011_BASE_ADDRESS: usize = 0x900_0000;
+pub const PL011_BASE_ADDRESS: *mut u32 = 0x900_0000 as _;
 // ANCHOR_END: imports
 
 /// Base address of the PL031 RTC.
-pub const PL031_BASE_ADDRESS: usize = 0x901_0000;
+pub const PL031_BASE_ADDRESS: *mut u32 = 0x901_0000 as _;
 
 // ANCHOR: main
 #[no_mangle]
 extern "C" fn main(x0: u64, x1: u64, x2: u64, x3: u64) {
     // Safe because `PL011_BASE_ADDRESS` is the base address of a PL011 device,
     // and nothing else accesses that address range.
-    let uart = unsafe { Uart::new(PL011_BASE_ADDRESS as *mut u32) };
+    let uart = unsafe { Uart::new(PL011_BASE_ADDRESS) };
     logger::init(uart, LevelFilter::Trace).unwrap();
 
     info!("main({:#x}, {:#x}, {:#x}, {:#x})", x0, x1, x2, x3);
@@ -50,7 +50,7 @@ extern "C" fn main(x0: u64, x1: u64, x2: u64, x3: u64) {
 
     // Safe because `PL031_BASE_ADDRESS` is the base address of a PL031 device,
     // and nothing else accesses that address range.
-    let rtc = unsafe { Rtc::new(PL031_BASE_ADDRESS as *mut u32) };
+    let rtc = unsafe { Rtc::new(PL031_BASE_ADDRESS) };
     let time = Utc.timestamp_opt(rtc.read().into(), 0).unwrap();
     info!("RTC: {}", time);