Add a convenience wrapper around the sdram slice

Author: oli-obk

examples/lcd.rs

@@ -55,8 +55,8 @@ fn main() -> ! {
         gpio_a, gpio_b, gpio_c, gpio_d, gpio_e, gpio_f, gpio_g, gpio_h, gpio_i, gpio_j, gpio_k,
     );
 
-    let sdram = init::init_sdram(&mut rcc, &mut fmc);
-    let (mut lcd, _sdram) = lcd::init(&mut ltdc, &mut rcc, sdram);
+    let mut sdram = init::init_sdram(&mut rcc, &mut fmc);
+    let mut lcd = lcd::init(&mut ltdc, &mut rcc, &mut sdram);
     pins.display_enable.set(true);
     pins.backlight.set(true);
 

src/bin/async-await.rs

@@ -102,8 +102,8 @@ fn run() -> ! {
     init::init_systick(Hz(100), &mut systick, &rcc);
     systick.enable_interrupt();
 
-    let sdram = init::init_sdram(&mut rcc, &mut fmc);
-    let (mut lcd, _sdram) = lcd::init(&mut ltdc, &mut rcc, sdram);
+    let mut sdram = init::init_sdram(&mut rcc, &mut fmc);
+    let mut lcd = lcd::init(&mut ltdc, &mut rcc, &mut sdram);
     pins.display_enable.set(true);
     pins.backlight.set(true);
 

src/bin/polling.rs

@@ -87,8 +87,8 @@ fn main() -> ! {
     init::init_systick(Hz(100), &mut systick, &rcc);
     systick.enable_interrupt();
 
-    let sdram = init::init_sdram(&mut rcc, &mut fmc);
-    let (mut lcd, _sdram) = lcd::init(&mut ltdc, &mut rcc, sdram);
+    let mut sdram = init::init_sdram(&mut rcc, &mut fmc);
+    let mut lcd = lcd::init(&mut ltdc, &mut rcc, &mut sdram);
     pins.display_enable.set(true);
     pins.backlight.set(true);
 

src/init/mod.rs

@@ -6,6 +6,7 @@ use stm32f7::stm32f7x6::{self as device, FLASH, FMC, PWR, RCC, SAI2, SYST};
 
 pub use self::pins::init as pins;
 pub use self::pins::Pins;
+use core::mem;
 
 mod pins;
 
@@ -147,10 +148,30 @@ pub fn enable_syscfg(rcc: &mut RCC) {
 
 static mut SDRAM_INITIALIZED: bool = false;
 
+/// SdRam allocator helper with some convenience methods
+pub struct SdRam(&'static mut [volatile::Volatile<u8>]);
+
+impl SdRam {
+    /// Allocates `size` bytes or panics if not enough memory available
+    ///
+    /// Note: it is not possible to free any memory
+    pub fn allocate(&mut self, size: usize) -> &'static mut [volatile::Volatile<u8>] {
+        let memory = mem::replace(&mut self.0, &mut []);
+        let (ret, rest) = memory.split_at_mut(size);
+        mem::replace(&mut self.0, rest);
+        ret
+    }
+
+    /// Yields the rest of the available memory
+    pub fn all(self) -> &'static mut [volatile::Volatile<u8>] {
+        self.0
+    }
+}
+
 /// Initializes the SDRAM, which makes more memory accessible.
 ///
 /// This is a prerequisite for using the LCD.
-pub fn init_sdram(rcc: &mut RCC, fmc: &mut FMC) -> &'static mut [volatile::Volatile<u8>] {
+pub fn init_sdram(rcc: &mut RCC, fmc: &mut FMC) -> SdRam {
 
     // ensures that we don't do this twice and end up with two `&'static mut` to the same memory
     unsafe {
@@ -302,7 +323,7 @@ pub fn init_sdram(rcc: &mut RCC, fmc: &mut FMC) -> &'static mut [volatile::Volat
     }
     // this block's safety is guaranteed by SDRAM_INITIALIZED check at the start of this function
     unsafe {
-        core::slice::from_raw_parts_mut(sdram_start as *mut volatile::Volatile<u8>, sdram_len)
+        SdRam(core::slice::from_raw_parts_mut(sdram_start as *mut volatile::Volatile<u8>, sdram_len))
     }
 }
 

src/lcd/init.rs

@@ -1,3 +1,4 @@
+use crate::init::SdRam;
 use super::Lcd;
 use stm32f7::stm32f7x6::{LTDC, RCC};
 
@@ -10,8 +11,8 @@ use stm32f7::stm32f7x6::{LTDC, RCC};
 pub fn init<'a>(
     ltdc: &'a mut LTDC,
     rcc: &mut RCC,
-    mem: &'static mut [volatile::Volatile<u8>],
-) -> (Lcd<'a>, &'static mut [volatile::Volatile<u8>]) {
+    mem: &mut SdRam,
+) -> Lcd<'a> {
     use crate::lcd;
     const HEIGHT: u16 = lcd::HEIGHT as u16;
     const WIDTH: u16 = lcd::WIDTH as u16;
@@ -156,8 +157,8 @@ pub fn init<'a>(
         w
     });
 
-    let (layer1, mem) = mem.split_at_mut(lcd::LAYER_1_LENGTH);
-    let (layer2, mem) = mem.split_at_mut(lcd::LAYER_2_LENGTH);
+    let layer1 = mem.allocate(lcd::LAYER_1_LENGTH);
+    let layer2 = mem.allocate(lcd::LAYER_2_LENGTH);
 
     // configure color frame buffer start address
     ltdc.l1cfbar
@@ -193,5 +194,5 @@ pub fn init<'a>(
 
     lcd.reload_shadow_registers(); // IMMEDIATE_RELOAD
 
-    (lcd, mem)
+    lcd
 }