Add font rendering

Makefile

@@ -7,7 +7,6 @@ CFLAGS=-Wall -Wextra -ffreestanding -march=armv8-a+crc -mcpu=cortex-a53
 DEBUG_FLAGS += -g -Og -DDEBUG -fno-omit-frame-pointer -fno-inline
 LDSCRIPT=rpi3.ld
 
-OBJS=crt0.o uart.o hello.o
 gasmsrc=$(wildcard *.S)
 gasmobj=$(gasmsrc:%.S=%.o)
 csrc=$(wildcard *.c)
@@ -18,12 +17,15 @@ KERNEL=kernel.bin
 
 all:$(KERNEL)
 
-kernel.elf: $(cobj) $(gasmobj) $(LDSCRIPT)
-	$(LD) $(LDFLAGS) -o $@ $(gasmobj) $(cobj) -T$(LDSCRIPT) -Map kernel.map
+kernel.elf: $(cobj) $(gasmobj) font_psf.o $(LDSCRIPT)
+	$(LD) $(LDFLAGS) -o $@ $(gasmobj) $(cobj) font_psf.o -T$(LDSCRIPT) -Map kernel.map
 
 $(KERNEL): kernel.elf
 	$(CROSS)objcopy -O binary $< $@
 
+font_psf.o: font.psf
+	$(LD) -r -b binary -o font_psf.o font.psf
+
 clean:
 	rm -rf $(cobj) $(gasmobj) $(deps) *.bin *.elf *.map
 

fb.c

@@ -12,7 +12,24 @@
 #define MBOX_TAG_FBSETPIXORD 0x48006
 #define MBOX_TAG_FBSETOFF 0x48009
 
-unsigned char *init_fb(struct fbst *fb) {
+/* PC Screen Font as used by Linux Console */
+typedef struct {
+  unsigned int magic;
+  unsigned int version;
+  unsigned int headersize;
+  unsigned int flags;
+  unsigned int numglyph;
+  unsigned int bytesperglyph;
+  unsigned int height;
+  unsigned int width;
+  unsigned char glyphs;
+} __attribute__((packed)) psf_t;
+extern volatile unsigned char _binary_font_psf_start;
+
+static struct fbst fb;
+
+unsigned char *fb_init()
+{
   // sending many tags at once
   mbox[0]  = 35 * 4;
   mbox[1]  = MBOX_REQUEST;
@@ -52,15 +69,64 @@ unsigned char *init_fb(struct fbst *fb) {
 
   if (mbox_call(MBOX_CH_PROP, mbox) == 0 && mbox[20] == 32 && mbox[28] != 0) {
     mbox[28] &= 0x3FFFFFFF; // convert GPU address to ARM address
-    fb->width = mbox[5];    // get actual physical width
-    fb->height = mbox[6];   // get actual physical height
-    fb->pitch = mbox[33];   // get number of bytes per line
-    fb->isrgb = mbox[24];   // get the actual channel order
-    fb->fbp = (void *)((unsigned long)mbox[28]);
+    fb.width  = mbox[5];   // get actual physical width
+    fb.height = mbox[6];   // get actual physical height
+    fb.pitch  = mbox[33];  // get number of bytes per line
+    fb.isrgb  = mbox[24];  // get the actual channel order
+    fb.fbp    = (void *)((unsigned long)mbox[28]);
   } else {
     puts("Unable to set framebuffer!\r\n");
     return 0;
   }
 
-  return fb->fbp;
+  return fb.fbp;
+}
+
+struct fbst * fb_get(){
+  return &fb;
+}
+
+void fb_print(int x, int y, char *s)
+{
+  // get our font
+  psf_t *font = (psf_t *)&_binary_font_psf_start;
+  // draw next character if it's not zero
+  while (*s) {
+    // get the offset of the glyph. Need to adjust this to support unicode table
+    unsigned char *glyph =
+        (unsigned char *)&_binary_font_psf_start + font->headersize +
+        (*((unsigned char *)s) < font->numglyph ? *s : 0) * font->bytesperglyph;
+    // calculate the offset on screen
+    int offs = (y * fb.pitch) + (x * 4);
+    // variables
+    int line, mask, bytesperline = (font->width + 7) / 8;
+    // handle carrige return
+    if (*s == '\r') {
+      x = 0;
+    } else
+      // new line
+      if (*s == '\n') {
+        x = 0;
+        y += font->height;
+      } else {
+        // display a character
+        for (unsigned int j = 0; j < font->height; j++) {
+          // display one row
+          line = offs;
+          mask = 1 << (font->width - 1);
+          for (unsigned int i = 0; i < font->width; i++) {
+            // if bit set, we use white color, otherwise black
+            *((unsigned int *)(fb.fbp + line)) = ((int)*glyph) & mask ? 0xFFFFFF : 0;
+            mask >>= 1;
+            line += 4;
+          }
+          // adjust to next line
+          glyph += bytesperline;
+          offs += fb.pitch;
+        }
+        x += (font->width + 1);
+      }
+    // next character
+    s++;
+  }
 }

fb.h

@@ -8,4 +8,6 @@ struct fbst {
     unsigned int isrgb;
 };
 
-unsigned char *init_fb(struct fbst *fb);
+unsigned char *fb_init();
+struct fbst * fb_get();
+void fb_print(int x, int y, char *s);

hello.c

@@ -3,11 +3,13 @@
 #include "uart.h"
 #include "utils.h"
 
-struct fbst fb;
 int kernelmain(void)
 {
-  init_uart();
-  if (init_fb(&fb) == 0) {
+  struct fbst *fb;
+  unsigned char *ptr;
+
+  uart_init();
+  if (fb_init() == 0) {
     puts("Fail to init framebuffer");
   }
   mbox[0] = 8 * 4;
@@ -32,10 +34,11 @@ int kernelmain(void)
 
   printclock();
 
-  unsigned char *ptr = fb.fbp;
+  fb  = fb_get();
+  ptr = fb->fbp;
 
-  for (unsigned int y = 0; y < fb.height; y++) {
-    for (unsigned int x = 0; x < fb.width; x++) {
+  for (unsigned int y = 0; y < fb->height; y++) {
+    for (unsigned int x = 0; x < fb->width; x++) {
       if (y % 60 == 0)
         *((unsigned int *)ptr) = 0x00FF0000;
       else if (y % 40 == 0)
@@ -47,5 +50,7 @@ int kernelmain(void)
       ptr += 4;
     }
   }
+
+  fb_print(0, 0, "Hello Dude\n");
   return 0;
 }

uart.c

@@ -4,7 +4,7 @@
 #include "gpio.h"
 
 
-void init_uart(void )
+void uart_init(void )
 {
 	//Active waiting
 	while(UART0_FR & (1<<3)){}

uart.h

@@ -11,6 +11,6 @@
 #define UART0_IMSC (*(volatile unsigned *)(UART0_BASE + 0x38))
 #define UART0_ICR (*(volatile unsigned *)(UART0_BASE + 0x44))
 
-void init_uart(void);
+void uart_init(void);
 void putc(char c);
 void puts(const char *s);