Improved framebuffer text scrolling mechanism

common/cmdline.c

@@ -70,6 +70,9 @@ string_cmd("com3", opt_com3);
 static char opt_com4[20];
 string_cmd("com4", opt_com4);
 
+bool opt_fb_scroll = true;
+bool_cmd("fb_scroll", opt_fb_scroll);
+
 const char *kernel_cmdline;
 
 void __text_init cmdline_parse(const char *cmdline) {

drivers/fb/fb.c

@@ -32,7 +32,11 @@
 
 extern uint64_t fonts[];
 
+#define FONT_SIZE           sizeof(fonts[0])
+#define TEXT_AREA_FIRST_ROW (((LOGO_HEIGHT + FONT_SIZE) / FONT_SIZE) * FONT_SIZE)
+
 static bool has_fb = false;
+static bool scroll = false;
 
 static uint32_t width;
 static uint32_t height;
@@ -43,6 +47,10 @@ static size_t buffer_size;
 static size_t banner_size;
 static void *video_memory;
 
+static void *first_line_addr;
+static void *last_line_addr;
+static uint64_t line_width;
+
 static void (*put_pixel)(uint32_t x, uint32_t y, uint32_t color);
 
 static void map_fb_area(paddr_t start, size_t size) {
@@ -82,7 +90,7 @@ void init_framebuffer(const struct multiboot2_tag_framebuffer *fb) {
     bpp = fb->common.framebuffer_bpp;
 
     buffer_size = (size_t) width * height;
-    banner_size = (size_t) width * LOGO_HEIGHT;
+    banner_size = (size_t) width * (LOGO_HEIGHT + FONT_SIZE);
 
     switch (bpp) {
     case 0 ... 7:
@@ -112,6 +120,10 @@ void init_framebuffer(const struct multiboot2_tag_framebuffer *fb) {
         BUG();
     }
 
+    line_width = pitch * FONT_SIZE;
+    first_line_addr = (uint8_t *) video_memory + TEXT_AREA_FIRST_ROW * pitch;
+    last_line_addr = (uint8_t *) video_memory + buffer_size - line_width;
+
     has_fb = true;
 }
 
@@ -123,14 +135,15 @@ bool setup_framebuffer(void) {
     memset(video_memory, 0, buffer_size);
 
     register_console_callback(fb_console_write, video_memory);
+    scroll = opt_fb_scroll;
     return true;
 }
 
 void put_char(char c, uint32_t x, uint32_t y, uint32_t color) {
     uint64_t font = fonts[(uint8_t) c];
 
-    for (int yy = 0; yy < 8; yy++) {
-        for (int xx = 0; xx < 8; xx++, font >>= 1) {
+    for (unsigned int yy = 0; yy < FONT_SIZE; yy++) {
+        for (unsigned int xx = 0; xx < FONT_SIZE; xx++, font >>= 1) {
             if (font & 1)
                 put_pixel(x + xx, y + yy, color);
         }
@@ -155,34 +168,54 @@ void draw_logo(void) {
             put_pixel(x, y, *px++);
     }
 
-    draw_line(0, LOGO_HEIGHT + 4, width, LOGO_HEIGHT + 4, FB_WHITE);
+    draw_line(0, LOGO_HEIGHT + 2, width, LOGO_HEIGHT + 2, FB_WHITE);
 }
 
-static void clear_screen(void *fb_addr) {
-    memset((uint8_t *) video_memory + banner_size, 0, buffer_size - banner_size);
+void set_fb_scroll(bool state) {
+    scroll = state;
+}
+
+static inline void scroll_up_line(void) {
+    memmove(first_line_addr, first_line_addr + line_width,
+            last_line_addr - first_line_addr);
+}
+
+static inline void clear_screen(void) {
+    memset(first_line_addr, 0, last_line_addr - first_line_addr);
 }
 
 void fb_write(void *fb_addr, const char *buf, size_t len, uint32_t color) {
-    static uint32_t row = LOGO_HEIGHT + 8, col = 0;
+    static uint32_t row = TEXT_AREA_FIRST_ROW, col = 0;
 
     for (unsigned int i = 0; i < len; i++) {
         char c = buf[i];
 
-        if ((col + 8) > width || c == '\n') {
-            row += sizeof(fonts[0]);
+        if ((col + FONT_SIZE) >= width || c == '\n') {
+            row += FONT_SIZE;
             col = 0;
         }
 
-        if ((row + 8) > height) {
-            clear_screen(fb_addr);
-            row = LOGO_HEIGHT + 8;
+        if ((row + FONT_SIZE) >= height) {
+            if (scroll) {
+                scroll_up_line();
+                row -= FONT_SIZE;
+            }
+            else {
+                clear_screen();
+                row = TEXT_AREA_FIRST_ROW;
+            }
             col = 0;
         }
 
+        if (c == '\r') {
+            col = 0;
+            continue;
+        }
+
         if (c == '\n')
             continue;
 
         put_char(c, col, row, color);
-        col += sizeof(fonts[0]);
+        col += FONT_SIZE;
     }
 }

include/cmdline.h

@@ -67,6 +67,7 @@ extern bool opt_hpet;
 extern bool opt_fpu;
 extern bool opt_qemu_console;
 extern bool opt_poweroff;
+extern bool opt_fb_scroll;
 
 extern const char *kernel_cmdline;
 

include/drivers/fb.h

@@ -36,5 +36,6 @@ extern void draw_line(uint32_t x1, uint32_t y1, uint32_t x2, uint32_t y2, uint32
 extern void draw_logo(void);
 extern void fb_write(void *fb_addr, const char *buf, size_t len, uint32_t color);
 extern bool setup_framebuffer(void);
+extern void set_fb_scroll(bool state);
 
 #endif /* KTF_DRV_FB_H */