Chatgpt wrote a crappy beeper

Makefile

@@ -44,7 +44,9 @@ OBJECTS = ./kernel/kstart.o ./kernel.o ./console.o ./drivers/vga.o ./drivers/uar
 	./fs/fs.o ./drivers/ata.o ./lib/string.o ./proc.o ./drivers/pit.o ./kernel/vm.o
 
 run: image.bin
-	qemu-system-i386 -drive format=raw,file=$< -serial mon:stdio -qmp unix:qemu-monitor-socket,server,nowait
+	qemu-system-i386 -drive format=raw,file=$< -serial mon:stdio -qmp unix:qemu-monitor-socket,server,nowait \
+	-audiodev pa,id=SAUND \
+    -machine pcspk-audiodev=SAUND
 
 run-nox: image.bin
 	qemu-system-i386 -nographic -drive format=raw,file=$< -serial mon:stdio -qmp unix:qemu-monitor-socket,server,nowait
@@ -106,7 +108,7 @@ debug-nox: image.bin
 		-ex "break _start" \
 		-ex "continue"
 
-USERPROGS=./user/false ./user/greet ./user/div0 ./user/shout ./user/badputs ./user/bss ./user/snake
+USERPROGS=./user/false ./user/greet ./user/div0 ./user/shout ./user/badputs ./user/bss ./user/snake ./user/player
 
 fs.img: ./kernel.bin ./tools/mkfs $(USERPROGS)
 	./tools/mkfs $@ $< $(USERPROGS)

cpu/idt.c

@@ -299,6 +299,13 @@ static void handle_syscall(registers_t* r) {
         case SYS_getc:
             r->eax = handle_getc();
             break;
+        case SYS_set_beep:
+            if (r->ebx > MAX_BEEP_FREQUENCY_HZ) {
+                userspace_panic("Userspace panic: beep frequency out of range\n");
+            }
+            set_beep_frequency_hz(r->ebx);
+            r->eax = 0;
+            break;
         default:
             userspace_panic("Userspace panic: Unknown syscall\n");
     }

drivers/pit.c

@@ -23,6 +23,11 @@ enum {
     PIT_MODES_SQUARE_WAVE_GENERATOR = 0x3,
     PIT_MODES_SW_TRIGGERRED_STROBE = 0x4,
     PIT_MODES_HW_TRIGGERRED_STROBE = 0x5,
+
+    PIT_COMMAND_PORT = 0x43,
+    PIT_CHANNEL0_DATA_PORT = 0x40,
+    PIT_CHANNEL2_DATA_PORT = 0x42,
+    PC_SPEAKER_PORT = 0x61,
 };
 
 
@@ -30,6 +35,7 @@ enum {
 static timer_callback callbacks[100];
 static int registered_callbacks = 0;
 static volatile uint32_t uptime_ms = 0;
+static volatile uint32_t speaker_frequency_hz = 0;
 
 void add_timer_callback(timer_callback tc) {
     callbacks[registered_callbacks++] = tc;
@@ -57,9 +63,9 @@ void init_pit() {
         .operating_mode = PIT_MODES_SQUARE_WAVE_GENERATOR,
         .bcd = 0,
     };
-    port_byte_out(0x43, *(unsigned char *)(&cmd));
-    port_byte_out(0x40, PIT_PROGRAM_REG & 0xff);
-    port_byte_out(0x40, (PIT_PROGRAM_REG & 0xff00) >> 8);
+    port_byte_out(PIT_COMMAND_PORT, *(unsigned char *)(&cmd));
+    port_byte_out(PIT_CHANNEL0_DATA_PORT, PIT_PROGRAM_REG & 0xff);
+    port_byte_out(PIT_CHANNEL0_DATA_PORT, (PIT_PROGRAM_REG & 0xff00) >> 8);
 
     register_interrupt_handler(IRQ0, timer_interrupt_handler);
     add_timer_callback(timer_int_callback);
@@ -76,6 +82,45 @@ uint32_t get_uptime_ms(void) {
     return uptime_ms;
 }
 
+void set_beep_frequency_hz(uint32_t frequency_hz) {
+    if (frequency_hz == 0) {
+        disable_beep();
+        return;
+    }
+
+    uint32_t divisor = PIT_CRYSTAL_HZ / frequency_hz;
+    if (divisor == 0) {
+        divisor = 1;
+    }
+    if (divisor > 0xffff) {
+        divisor = 0xffff;
+    }
+
+    struct pit_command_t cmd = {
+        .select_channel = PIT_SELECT_CHANNEL2,
+        .access_mode = PIT_ACCESS_MODE_LOHIBYTE,
+        .operating_mode = PIT_MODES_SQUARE_WAVE_GENERATOR,
+        .bcd = 0,
+    };
+    port_byte_out(PIT_COMMAND_PORT, *(unsigned char *)(&cmd));
+    port_byte_out(PIT_CHANNEL2_DATA_PORT, divisor & 0xff);
+    port_byte_out(PIT_CHANNEL2_DATA_PORT, (divisor & 0xff00) >> 8);
+
+    uint8_t speaker = port_byte_in(PC_SPEAKER_PORT);
+    port_byte_out(PC_SPEAKER_PORT, speaker | 0x03);
+    speaker_frequency_hz = frequency_hz;
+}
+
+void disable_beep(void) {
+    uint8_t speaker = port_byte_in(PC_SPEAKER_PORT);
+    port_byte_out(PC_SPEAKER_PORT, speaker & 0xfc);
+    speaker_frequency_hz = 0;
+}
+
+uint32_t get_beep_frequency_hz(void) {
+    return speaker_frequency_hz;
+}
+
 void msleep(int ms) {
     sleep_counter = ms / 10;
     while (sleep_counter > 0) {

drivers/pit.h

@@ -2,10 +2,15 @@
 
 #include <stdint.h>
 
+#define MAX_BEEP_FREQUENCY_HZ 44100u
+
 typedef void (*timer_callback)(void);
 
 void init_pit(void);
 void add_timer_callback(timer_callback tc);
 
 uint32_t get_uptime_ms(void);
+void set_beep_frequency_hz(uint32_t frequency_hz);
+void disable_beep(void);
+uint32_t get_beep_frequency_hz(void);
 void msleep(int ms);

proc.c

@@ -1,4 +1,5 @@
 #include "proc.h"
+#include "drivers/pit.h"
 #include "drivers/vga.h"
 
 struct context {
@@ -88,6 +89,7 @@ void run_elf(const char* name) {
 
 _Noreturn void killproc() {
     void* task_stack;
+    disable_beep();
     if (!vga_is_text_mode()) {
         switch_to_text_mode();
         vga_clear_screen();

syscall.h

@@ -14,6 +14,7 @@ enum {
 	SYS_time_ms = 7,
 	SYS_halt = 8,
 	SYS_getc = 9,
+	SYS_set_beep = 10,
 };
 
 int syscall(int call, uintptr_t arg);

user/player.c

@@ -0,0 +1,24 @@
+#include "../syscall.h"
+#include <stdint.h>
+
+static uint32_t time_ms(void) {
+    return (uint32_t)syscall(SYS_time_ms, 0);
+}
+
+static void wait_ms(uint32_t duration_ms) {
+    uint32_t start = time_ms();
+    while ((uint32_t)(time_ms() - start) < duration_ms) {
+        syscall(SYS_halt, 0);
+    }
+}
+
+int main(void) {
+    syscall(SYS_set_beep, 10000);
+    wait_ms(1000);
+
+    syscall(SYS_set_beep, 15000);
+    wait_ms(1000);
+
+    // syscall(SYS_set_beep, 0);
+    return 0;
+}