diff --git a/include/bga.h b/include/bga.h
index 5e42e41..06ea44d 100644
--- a/include/bga.h
+++ b/include/bga.h
@@ -2,11 +2,15 @@
 #include "pci.h"
 #include "type.h"
 
-#define BGA_SWAP_BUFFERS 0x0101
-#define BGA_GET_HEIGHT 0x0102
-#define BGA_GET_WIDTH 0x0103
-#define BGA_GET_SCALE 0x0104
-#define BGA_DISABLE 0x0105
+#define BGA_SWAP_BUFFERS    0x0101
+#define BGA_GET_HEIGHT      0x0102
+#define BGA_GET_WIDTH       0x0103
+#define BGA_GET_SCALE       0x0104
+#define BGA_DISABLE         0x0105
+#define BGA_SET_WIDTH       0x0106
+#define BGA_SET_HEIGHT      0x0107
+#define BGA_SET_UPDATE      0x0108
+#define BGA_GET_BUFFER      0x0109
 
-int bga_init_with_dev(pci_dev_t* dev);
+int init_bga(pci_dev_t* dev);
 int bga_ioctl(uintptr_t cmd, uintptr_t arg);
\ No newline at end of file
diff --git a/kernel/bga.c b/kernel/bga.c
index 9028eb6..dda6038 100644
--- a/kernel/bga.c
+++ b/kernel/bga.c
@@ -1,19 +1,20 @@
-#include "type.h"
+#include "bga.h"
+
 #include "assert.h"
 #include "console.h"
 #include "const.h"
+#include "global.h"
 #include "keyboard.h"
 #include "memman.h"
+#include "pci.h"
 #include "proc.h"
 #include "protect.h"
 #include "proto.h"
 #include "stdio.h"
 #include "string.h"
-#include "x86.h"
-#include "global.h"
 #include "tty.h"
-#include "pci.h"
-#include "bga.h"
+#include "type.h"
+#include "x86.h"
 
 #define VBE_DISPI_IOPORT_INDEX 0x01CE
 #define VBE_DISPI_IOPORT_DATA 0x01CF
@@ -37,20 +38,17 @@ static uint16_t bga_screen_width, bga_screen_height;
 static uint32_t bga_screen_line_size, bga_screen_buffer_size;
 static uint32_t bga_buf_paddr;
 
-static inline void _bga_write_reg(uint16_t cmd, uint16_t data)
-{
+static inline void _bga_write_reg(uint16_t cmd, uint16_t data) {
     outw(VBE_DISPI_IOPORT_INDEX, cmd);
     outw(VBE_DISPI_IOPORT_DATA, data);
 }
 
-static inline uint16_t _bga_read_reg(uint16_t cmd)
-{
+static inline uint16_t _bga_read_reg(uint16_t cmd) {
     outw(VBE_DISPI_IOPORT_INDEX, cmd);
     return inw(VBE_DISPI_IOPORT_DATA);
 }
 
-static void _bga_set_resolution(uint16_t width, uint16_t height)
-{
+static void _bga_set_resolution(uint16_t width, uint16_t height) {
     _bga_write_reg(VBE_DISPI_INDEX_ENABLE, VBE_DISPI_DISABLED);
     _bga_write_reg(VBE_DISPI_INDEX_XRES, width);
     _bga_write_reg(VBE_DISPI_INDEX_YRES, height);
@@ -59,82 +57,79 @@ static void _bga_set_resolution(uint16_t width, uint16_t height)
     _bga_write_reg(VBE_DISPI_INDEX_BPP, 32);
     _bga_write_reg(VBE_DISPI_INDEX_X_OFFSET, 0);
     _bga_write_reg(VBE_DISPI_INDEX_Y_OFFSET, 0);
-    _bga_write_reg(VBE_DISPI_INDEX_ENABLE, VBE_DISPI_ENABLED | VBE_DISPI_LFB_ENABLED);
+    _bga_write_reg(VBE_DISPI_INDEX_ENABLE,
+                   VBE_DISPI_ENABLED | VBE_DISPI_LFB_ENABLED);
     _bga_write_reg(VBE_DISPI_INDEX_BANK, 0);
 
     bga_screen_line_size = (uint32_t)width * 4;
 }
 
-int bga_ioctl(uintptr_t cmd, uintptr_t arg)
-{
-    uint32_t y_offset = 0;
-    switch (cmd) {
-    case BGA_GET_HEIGHT:
-        return bga_screen_height;
-    case BGA_GET_WIDTH:
-        return bga_screen_width;
-    case BGA_GET_SCALE:
-        return 1;
-    case BGA_SWAP_BUFFERS:
-        y_offset = bga_screen_height * (arg & 1);
-        _bga_write_reg(VBE_DISPI_INDEX_Y_OFFSET, (uint16_t)y_offset);
-        return 0;
-    case BGA_DISABLE:
-        _bga_write_reg(VBE_DISPI_INDEX_ENABLE, VBE_DISPI_DISABLED);
-        return 0;
-    default:
-        return -1;
-    }
-}
-
-// static memzone_t* _bga_mmap(file_t* file, mmap_params_t* params)
-// {
-//     bool map_shared = ((params->flags & MAP_SHARED) > 0);
-
-//     if (!map_shared) {
-//         return 0;
-//     }
-
-//     memzone_t* zone = memzone_new_random(RUNNING_THREAD->process->address_space, bga_screen_buffer_size);
-//     if (!zone) {
-//         return 0;
-//     }
-
-//     zone->mmu_flags |= MMU_FLAG_PERM_WRITE | MMU_FLAG_PERM_READ | MMU_FLAG_UNCACHED;
-//     zone->type |= ZONE_TYPE_DEVICE;
-//     zone->file = file_duplicate(file);
-//     zone->ops = &mmap_file_vm_ops;
-
-//     for (int offset = 0; offset < bga_screen_buffer_size; offset += VMM_PAGE_SIZE) {
-//         vmm_map_page(zone->vaddr + offset, bga_buf_paddr + offset, zone->mmu_flags);
-//     }
-
-//     return zone;
-// }
-
-
-static void bga_set_resolution(uint32_t width, uint32_t height)
-{
+static void bga_set_resolution(uint32_t width, uint32_t height) {
     _bga_set_resolution(width, height);
     bga_screen_width = width;
     bga_screen_height = height;
     bga_screen_buffer_size = bga_screen_line_size * height * 2;
 }
 
+int bga_ioctl(uintptr_t cmd, uintptr_t arg) {
+    uint32_t y_offset = 0;
+    switch (cmd) {
+        case BGA_GET_HEIGHT:
+            return bga_screen_height;
+        case BGA_GET_WIDTH:
+            return bga_screen_width;
+        case BGA_GET_SCALE:
+            return 1;
+        case BGA_GET_BUFFER:
+            if (arg == 0)
+                return bga_buf_paddr;
+            else
+                return bga_buf_paddr + bga_screen_buffer_size / 2;
+        case BGA_SWAP_BUFFERS:
+            y_offset = bga_screen_height * (arg & 1);
+            _bga_write_reg(VBE_DISPI_INDEX_Y_OFFSET, (uint16_t)y_offset);
+            return 0;
+        case BGA_DISABLE:
+            _bga_write_reg(VBE_DISPI_INDEX_ENABLE, VBE_DISPI_DISABLED);
+            return 0;
+        case BGA_SET_WIDTH:
+            bga_screen_width = arg;
+            return 0;
+        case BGA_SET_HEIGHT:
+            bga_screen_height = arg;
+            return 0;
+        case BGA_SET_UPDATE:
+            bga_set_resolution(bga_screen_width, bga_screen_height);
+            return 0;
+        default:
+            return -1;
+    }
+}
 
-int bga_init_with_dev(pci_dev_t* dev)
-{
+int init_bga(pci_dev_t *dev) {
     if (dev->type != DEVICE_DISPLAY) {
         return -1;
     }
 
     bga_buf_paddr = pci_read_bar(dev, 0) & 0xfffffff0;
     bga_set_resolution(1024, 768);
-    kprintf("bga buf paddr=%p; buf size= %d KB\n", bga_buf_paddr, bga_screen_buffer_size / 1024);
+    kprintf("bga buf paddr=%p; buf size= %d KB\n", bga_buf_paddr,
+            bga_screen_buffer_size / 1024);
     for (int k = 0; k < bga_screen_buffer_size; k += 4096) {
-	    klin_mapping_phy(bga_buf_paddr + k, bga_buf_paddr + k, PG_P | PG_USU | PG_RWW, PG_P | PG_USU | PG_RWW);
+        klin_mapping_phy(bga_buf_paddr + k, bga_buf_paddr + k,
+                         PG_P | PG_USU | PG_RWW, PG_P | PG_USU | PG_RWW);
     }
-    uint32_t *test = (uint32_t *)bga_buf_paddr;
-    for (int i = 0; i <= 1024*20; ++ i) test[i] = 0xff3312;
+    // uint32_t *test = (uint32_t *)bga_buf_paddr;
+    // uint32_t *test2 = (uint32_t *)(bga_buf_paddr + bga_screen_buffer_size / 2);
+    // for (int i = 0; i <= 1024 * 20; ++i) test[i] = 0x00ff12;
+    // for (int i = 1024 * 20; i <= 1024 * 40; ++i) test2[i] = 0x0000ff;
+    // while (1) {
+    //     bga_ioctl(BGA_SWAP_BUFFERS, 1);
+    //     for (volatile int i = 0; i < 0x03ffffff; ++i)
+    //         ;
+    //     bga_ioctl(BGA_SWAP_BUFFERS, 0);
+    //     for (volatile int i = 0; i < 0x03ffffff; ++i)
+    //         ;
+    // }
     return 0;
 }
\ No newline at end of file
diff --git a/kernel/main.c b/kernel/main.c
index 93d8cd9..bd1ebd4 100644
--- a/kernel/main.c
+++ b/kernel/main.c
@@ -47,7 +47,7 @@ int kernel_main()
 	init_tty_main();
 	init_pci();
 	pci_dev_t* dev_bga = get_pci_bga();
-	bga_init_with_dev(dev_bga);
+	init_bga(dev_bga);
 	kprintf("cr3 ready= %p\n", cr3_ready);
 	// initialize PCBs, added by xw, 18/5/26
 	error = initialize_processes();