dont use mutex on framebuffer

kernel/src/abi.rs

@@ -12,7 +12,7 @@ use embedded_graphics::{
 };
 use shared::keyboard::KeyEvent;
 
-use crate::{KEY_CACHE, display::access_framebuffer_blocking};
+use crate::{KEY_CACHE, display::framebuffer_mut};
 
 // ensure the abi and the kernel fn signatures are the same
 const _: PrintAbi = print;
@@ -25,17 +25,8 @@ pub extern "Rust" fn print(msg: &str) {
 
 // TODO: maybe return result
 pub extern "Rust" fn draw_iter(pixels: &[Pixel<Rgb565>]) {
-    loop {
+    let fb = framebuffer_mut();
-        if access_framebuffer_blocking(|fb| {
     fb.draw_iter(pixels.iter().copied()).unwrap();
-        })
-        .is_ok()
-        {
-            break;
-        }
-
-        cortex_m::asm::nop();
-    }
 }
 
 pub extern "Rust" fn get_key() -> Option<KeyEvent> {

kernel/src/display.rs

@@ -20,24 +20,10 @@ pub const SCREEN_WIDTH: usize = 320;
 pub const SCREEN_HEIGHT: usize = 320;
 
 type FB = FrameBuffer<SCREEN_WIDTH, SCREEN_HEIGHT, { SCREEN_WIDTH * SCREEN_HEIGHT }>;
-static FRAMEBUFFER_CELL: StaticCell<FB> = StaticCell::new();
+static mut FRAMEBUFFER: Option<FB> = None;
-static FRAMEBUFFER: Mutex<CriticalSectionRawMutex, Option<&'static mut FB>> = Mutex::new(None);
 
-pub fn access_framebuffer_blocking(mut access: impl FnMut(&mut FB)) -> Result<(), ()> {
+pub fn framebuffer_mut() -> &'static mut FB {
-    let mut guard = FRAMEBUFFER.try_lock().ok().ok_or(())?;
+    unsafe { FRAMEBUFFER.as_mut().unwrap() }
-    let fb = guard.as_mut().ok_or(())?;
-    access(fb);
-    Ok(())
-}
-
-pub async fn access_framebuffer(mut access: impl FnMut(&mut FB)) -> Result<(), ()> {
-    let mut guard = FRAMEBUFFER.lock().await;
-    let fb: Option<&mut &'static mut FB> = guard.as_mut();
-    if let Some(fb) = fb {
-        access(&mut *fb);
-        return Ok(());
-    }
-    Err(())
 }
 
 pub async fn init_display(
@@ -58,19 +44,17 @@ pub async fn init_display(
 
     display.init().await.unwrap();
     display.set_custom_orientation(0x40).await.unwrap();
-    let mut framebuffer = FRAMEBUFFER_CELL.init(FrameBuffer::new());
+    unsafe { FRAMEBUFFER.replace(FrameBuffer::new()) };
-    display.draw(&mut framebuffer).await.unwrap();
+    display.draw(framebuffer_mut()).await.unwrap();
     display.set_on().await.unwrap();
-    FRAMEBUFFER.lock().await.replace(framebuffer);
 
     display
 }
 
-static DISPLAYREF: StaticCell<DISPLAY> = StaticCell::new();
-
 pub async fn display_handler(mut display: DISPLAY) {
-    let mut guard = FRAMEBUFFER.lock().await;
+    let fb = framebuffer_mut();
-    if let Some(fb) = guard.as_mut() {
+    loop {
         display.partial_draw_batched(fb).await.unwrap();
+        embassy_time::Timer::after_millis(32).await; // 30 fps
     }
 }

kernel/src/main.rs

@@ -18,7 +18,7 @@ mod usb;
 mod utils;
 
 use crate::{
-    display::{access_framebuffer, display_handler, init_display},
+    display::{display_handler, framebuffer_mut, init_display},
     peripherals::{
         conf_peripherals,
         keyboard::{KeyCode, KeyState, read_keyboard_fifo},
@@ -139,11 +139,10 @@ async fn userland_task() {
             TASK_STATE_CHANGED.signal(());
         }
 
-        access_framebuffer(|fb| {
+        {
+            let fb = framebuffer_mut();
             fb.clear(Rgb565::BLACK).unwrap();
-        })
+        }
-        .await
-        .unwrap();
 
         defmt::info!("running entry");
         entry().await;

kernel/src/ui.rs

@@ -1,6 +1,6 @@
 use crate::{
     BINARY_CH, TASK_STATE, TaskState,
-    display::{SCREEN_HEIGHT, SCREEN_WIDTH, access_framebuffer},
+    display::{SCREEN_HEIGHT, SCREEN_WIDTH, framebuffer_mut},
     elf::load_binary,
     format,
     peripherals::keyboard,
@@ -102,8 +102,7 @@ async fn draw_selection() {
         guard.selections.clone()
     };
 
-    loop {
+    let fb = framebuffer_mut();
-        if access_framebuffer(|fb|{
     let text_style = MonoTextStyle::new(&FONT_9X15, Rgb565::WHITE);
     let display_area = fb.bounding_box();
 
@@ -147,14 +146,6 @@ async fn draw_selection() {
             .draw(fb)
             .unwrap();
     };
-    }
-        ).await.is_ok() {
-            break;
-        }
-
-        defmt::warn!("Failed to draw selection: framebuffer unavailable");
-        Timer::after_micros(10).await;
-    }
 }
 
 #[derive(Clone)]