implement proper IRQL, DPCs, kernel and user APCs, alertable waits, async file I/O with cancellation, trap frames, selftests, a real driver/device model, native async FAT32, VFAT dotfile fixes, syscall ABI cleanup, async_apc and async_cancel tests, POSIX multi-volume paths, and pimp the readme.

code/hal/hal_mouse.c

@@ -13,15 +13,15 @@
 //   Byte 2:  delta-Y unsigned magnitude (sign in byte-0 bit 5); PS/2 Y+ = up
 //
 // The ISR accumulates the 3-byte packet, converts it to a screen-space delta
-// (Y-axis flipped), clamps the absolute position to [0, bounds), enqueues a
-// MOUSE_EVENT, and then calls EraseOldCursor / DrawNewCursor via the two
-// screen helpers that hal_screen.c exports.
+// (Y-axis flipped), and queues the completed packet to the HAL's kernel-queued
+// bottom half.  Cursor drawing, public event enqueue, and optional callbacks
+// run from that bottom half instead of hard IRQ context.
 //
 // Threading model
 // ---------------
-//   Single-producer (ISR on IRQ 12) / single-consumer ring buffer.
-//   All ISR-written fields are volatile; on a uniprocessor this is sufficient.
-//   On SMP, add acquire/release barriers around gHead / gTail.
+//   Public events are produced by the mouse DPC and consumed by callers.
+//   Raw completed packets are produced by the ISR and consumed by the same DPC.
+//   On SMP, add acquire/release barriers around the ring head/tail pairs.
 
 #include <stdint.h>
 #include <stdbool.h>
@@ -44,8 +44,13 @@ typedef struct {
 } MOUSE_EVENT;
 
 static MOUSE_EVENT  gBuf[MOUSE_BUF_SIZE];
-static volatile int gHead = 0;   // consumer read pointer
-static volatile int gTail = 0;   // producer write pointer (updated by ISR)
+static volatile int gHead = 0;   // public consumer read pointer
+static volatile int gTail = 0;   // public producer write pointer (updated by DPC)
+
+// Completed hardware packets waiting for the DPC bottom half.
+static MOUSE_EVENT  gDpcBuf[MOUSE_BUF_SIZE];
+static volatile int gDpcHead = 0;
+static volatile int gDpcTail = 0;
 
 // -- Absolute cursor position & screen bounds ----------------------------------
 static volatile int gMouseX  = 0;
@@ -57,7 +62,7 @@ static volatile int gBoundsH = 1080;
 static volatile uint8_t gPacket[3];
 static volatile int     gPacketIdx = 0;   // 0, 1, or 2
 
-// -- Optional callback (called from ISR) ---------------------------------------
+// -- Optional callback (called from mouse DPC) ---------------------------------
 static void (* volatile gCallback)(int dx, int dy, uint8_t buttons) = NULL;
 
 // -- Cursor helpers provided by hal_screen.c -----------------------------------
@@ -101,9 +106,45 @@ static uint8_t MouseRecvByte(void) {
     return __inbyte(PS2_DATA);
 }
 
+// -- Deferred mouse bottom half -------------------------------------------------
+static void MouseDpc(void) {
+    for (;;) {
+        if (gDpcHead == gDpcTail)
+            break;
+
+        MOUSE_EVENT ev = gDpcBuf[gDpcHead];
+        gDpcHead = (gDpcHead + 1) & (int)MOUSE_BUF_MASK;
+
+        // Update absolute position and redraw the cursor outside DIRQL.
+        HalScreenEraseCursor();
+
+        int nx = gMouseX + ev.dx;
+        int ny = gMouseY + ev.dy;
+        if (nx < 0)             nx = 0;
+        if (nx >= gBoundsW)     nx = gBoundsW - 1;
+        if (ny < 0)             ny = 0;
+        if (ny >= gBoundsH)     ny = gBoundsH - 1;
+        gMouseX = nx;
+        gMouseY = ny;
+
+        HalScreenDrawCursor(nx, ny);
+
+        // Publish event to the normal consumer ring.
+        int next = (gTail + 1) & (int)MOUSE_BUF_MASK;
+        if (next != gHead) {
+            gBuf[gTail] = ev;
+            gTail = next;
+        }
+
+        void (*cb)(int, int, uint8_t) = (void (*)(int, int, uint8_t))gCallback;
+        if (cb)
+            cb(ev.dx, ev.dy, ev.buttons);
+    }
+}
+
 // -- Interrupt service routine --------------------------------------------------
 // Called with interrupts disabled by KeIrqDispatch (IRQ 12).
-// The dispatcher sends the APIC EOI before this function is invoked.
+// The dispatcher sends the APIC EOI after this function returns.
 static void MouseIsr(void) {
     uint8_t data = __inbyte(PS2_DATA);
 
@@ -130,32 +171,14 @@ static void MouseIsr(void) {
     int dy = (int)gPacket[2] - ((flags & 0x20u) ? 256 : 0);
     dy = -dy;   // PS/2 Y+ = up; screen Y+ = down, so invert.
 
-    // -- Update absolute position (clamped to screen bounds) ------------------
-    HalScreenEraseCursor();
-
-    int nx = gMouseX + dx;
-    int ny = gMouseY + dy;
-    if (nx < 0)             nx = 0;
-    if (nx >= gBoundsW)     nx = gBoundsW - 1;
-    if (ny < 0)             ny = 0;
-    if (ny >= gBoundsH)     ny = gBoundsH - 1;
-    gMouseX = nx;
-    gMouseY = ny;
-
-    HalScreenDrawCursor(nx, ny);
-
-    // -- Enqueue event; silently drop if buffer is full -----------------------
-    int next = (gTail + 1) & (int)MOUSE_BUF_MASK;
-    if (next != gHead) {
-        gBuf[gTail].dx      = dx;
-        gBuf[gTail].dy      = dy;
-        gBuf[gTail].buttons = buttons;
-        gTail               = next;
+    // -- Queue completed packet to the DPC bottom half -------------------------
+    int next = (gDpcTail + 1) & (int)MOUSE_BUF_MASK;
+    if (next != gDpcHead) {
+        gDpcBuf[gDpcTail].dx      = dx;
+        gDpcBuf[gDpcTail].dy      = dy;
+        gDpcBuf[gDpcTail].buttons = buttons;
+        gDpcTail                  = next;
     }
-
-    // -- Optional callback (raw ISR context) -----------------------------------
-    void (*cb)(int, int, uint8_t) = (void (*)(int, int, uint8_t))gCallback;
-    if (cb) cb(dx, dy, buttons);
 }
 
 // -- Consumer API --------------------------------------------------------------
@@ -278,5 +301,6 @@ void HalMouseInitialize(HAL_MOUSE* out, int screenW, int screenH) {
     out->SetPosition = MouseSetPosition;
     out->SetBounds   = MouseSetBounds;
     out->Isr         = MouseIsr;
+    out->Dpc         = MouseDpc;
     out->IrqNumber   = 12;
 }