SVC calls

.gitignore

@@ -1,2 +1,3 @@
 out/*
 main.hex
+initrd.img

include/lcd.h

@@ -3,6 +3,9 @@
 
 #include <stdint.h>
 
+/**
+ * Direct access
+ */
 void lcd_init(void);
 
 void lcd_puts(const char *s);
@@ -11,4 +14,10 @@ void lcd_puth(int h);
 void lcd_putb(uint8_t b);
 void lcd_clear(void);
 
+/**
+ * Buffered/async access
+ */
+void lcd_handler(void);
+void lcd_put(const char *s);
+
 #endif // LCD_H_

src/lcd.c

@@ -1,6 +1,7 @@
 #include <lcd.h>
 #include <clock.h>
 #include <gpio.h>
+#include <string.h>
 
 #define LCD_D0 GPIO_PORT(A, 0)
 #define LCD_D1 GPIO_PORT(A, 1)
@@ -115,3 +116,38 @@ void lcd_init(void)
 	delay(5);
 	lcd_clear();
 }
+
+/**
+ * Task code
+ */
+
+static int bufpos = 0;
+static char buf[64];
+void lcd_clearbuf(void)
+{
+	bufpos = 0;
+	for (int i = 0; i < 32; i++)
+		buf[i] = 0;
+}
+
+void lcd_put(const char *s)
+{
+	int len = strlen(s);
+	int off = (bufpos + len < 64) ? len : 64 - bufpos;
+	strncpy(buf + bufpos, s, off);
+	bufpos += off;
+}
+
+void lcd_handler(void)
+{
+	lcd_init();
+	lcd_clearbuf();
+
+	while (1) {
+		if (buf[0] != '\0') {
+			lcd_puts(buf);
+			lcd_clearbuf();
+		}
+		delay(100);
+	}
+}

src/main.c

@@ -45,12 +45,20 @@ void kmain(void)
 {
 	asm("cpsie i");
 
-	lcd_init();
+	task_start(lcd_handler, 128);
+	delay(200);
 
 	char *s = initrd_getfile("test.txt");
-	lcd_puts(s);
+	const char *t = "Yoyoyo";
 
-	while (1)
+	asm("mov r0, %0; svc 2" :: "r" (s));
-		delay(100);
+	asm("mov r0, %0; svc 2" :: "r" (t));
+
+	while (1) {
+		gpio_dout(GPIOA, 5, 1);
+		delay(500);
+		gpio_dout(GPIOA, 5, 0);
+		delay(500);
+	}
 }
 

src/stm32l4xx_it.c

@@ -4,31 +4,27 @@ void NMI_Handler(void) {}
 
 void HardFault_Handler(void)
 {
-	GPIOA->BSRR |= (1 << 5) | (1 << 6);
+	GPIOA->BSRR |= (1 << 5);
 	while (1);
 }
 
 void MemManage_Handler(void)
 {
-	GPIOA->BSRR |= (1 << 5) | (1 << 6);
+	GPIOA->BSRR |= (1 << 5);
 	while (1);
 }
 
 void BusFault_Handler(void)
 {
-	GPIOA->BSRR |= (1 << 5) | (1 << 6);
+	GPIOA->BSRR |= (1 << 5);
 	while (1);
 }
 
 void UsageFault_Handler(void)
 {
-	GPIOA->BSRR |= (1 << 5) | (1 << 6);
+	GPIOA->BSRR |= (1 << 5);
 	while (1);
 }
 
-void SVC_Handler(void) {
-
-}
-
 void DebugMon_Handler(void) {}
 

src/svc.c

@@ -0,0 +1,33 @@
+#include <stdint.h>
+#include <gpio.h>
+#include <clock.h>
+#include <lcd.h>
+
+void SVC_Handler(void) {
+	uint32_t *stack;
+	uint8_t index;
+
+	asm("\
+		mrs r0, psp; \
+		mov %0, r0; \
+		ldr r0, [r0, #24]; \
+		ldr %1, [r0, #-2]; \
+	" : "=r" (stack), "=r" (index));
+
+	gpio_mode(GPIOA, 6, OUTPUT);
+
+	switch (index) {
+	case 1:
+		gpio_dout(GPIOA, 6, 1);
+		for (int i = 0; i < 100000; i++)
+			asm("");
+		gpio_dout(GPIOA, 6, 0);
+		break;
+	case 2:
+		lcd_put((char *)stack[0]);
+		break;
+	default:
+		break;
+	}
+}
+