linux驱动开发之应用程序控制LCD屏

1, 打开设备

int fd = open(“/dev/fb0”, O_RDWR);

2, 获取到lcd屏的信息xres, yres, bpp

struct fb_var_screeninfo var;//var是容器，用来存放数据

ioctl(fd, FBIOGET_VSCREENINFO, &var);//FBIOGET_VSCREENINFO表示获取可变屏幕信息，以后看到GET，一般表示拿东西，这里向驱动拿
|
.unlocked_ioctl = fb_ioctl,
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struct fb_info *info = file_fb_info(file);//
|//从registered_fb数组中得到fb_info
struct fb_info *info = registered_fb[fbidx];
do_fb_ioctl(info, cmd, arg);
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void __user *argp = (void __user *)arg;
switch (cmd) {
case FBIOGET_VSCREENINFO:
var = info->var;
copy_to_user(argp, &var, sizeof(var)) ? -EFAULT : 0;

size_t length = var.xres * var.yres * var.bits_per_pixel / 8

3,映射显存（一帧）到用户空间

//返回一个地址
char *addr = mmap(NULL, size_t length, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);

framebuffer_ptr =(char *)mmap(  NULL,//如果此值为NULL,则表示用内核来自动给你分配一块虚拟空间
screensize,        //空间大小
PROT_READ|PROT_WRITE,//权限
MAP_SHARED,        //是否可以共享
framebuffer_fd,        //文件描述符
0);            //从哪个地方开始

4, 得到图片数据,将数据写入到addr

/*1.打开一副图片*/
pic_fd =open(argv[2],O_RDWR);
printf("pic_fd=%d\n",pic_fd);

/*2.获取图片大小*/
len =lseek(pic_fd, 0, SEEK_END);//SEEK_END表示定位到一个文件的末尾
printf("len =%ld\n",len);

buffer =(char *)malloc(len);

lseek(pic_fd, 0, SEEK_SET);
/*3.读取图片数据*/
read(pic_fd,buffer,len);

// buffer 存了bmp的图片数据, framebuffer_ptr映射之后的显存位置
draw_bmp(buffer,(unsigned short *) framebuffer_ptr);
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bmp_read_file(bmpfilename, &bmpdata);//跳过bmp文件头
bmp2fb16_rgb565(bmpdata, fb);
|//bmp2fb16_rgb565(unsigned char *bmpdata,unsigned short *fb16)
fb16_buff = fb16; //  fb16_buff就是framebuffer_ptr,映射之后的显存位置
for (y = ysize; y > 0 ; y--)
{
for (x = 0 ; x < xsize; x++) /*copy one line to frame buffer*/
{
/*copy one pixel to frame buffer*/
b = *bmpdata;
bmpdata++;
b >>= 3;
g = *bmpdata;
bmpdata++;
g >>= 2;
r = *bmpdata;
bmpdata++;
r >>= 3;
pixel16 = (unsigned short) ((r << 11) | (g << 5) | b);
*( fb16_buff +  (y* xsize + x)  ) = pixel16;//将一个像素填写到显存
}
}

程序文件：链接：https://pan.baidu.com/s/1ggeHO1H 密码：yfvz



lcd.test是主程序

jpeg2bmp.o是图片数据格式的解析

framebuffer.o是初始化framebuffer子系统

把lcd_test复制到指定路径中：cp lcd_test *.bmp /opt/rootfs/drv_module/

在开发板执行命令./lcd_test /dev/fb0 logo_girl_800*480.bmp

出现以下调试信息



程序阻塞在这里，等待用户的输出（输入1显示图片，输入2显示文字）

附录：

readme.txt

1.用bmp文件 800*480
2.注意 x,y参数 800 ,480
unsigned int bpp    =16;
unsigned int xsize  =800;
unsigned int ysize  =480;

在mach-smkv210.c 查看并修改.
static struct s3c_fb_pd_win smdkv210_fb_win0 = {
/*
.win_mode = {
.left_margin    = 13,
.right_margin   = 8,
.upper_margin   = 7,
.lower_margin   = 5,
.hsync_len  = 3,
.vsync_len  = 1,
.xres       = 800,
.yres       = 480,
},
.max_bpp    = 32,
.default_bpp    = 24,
*/

.win_mode = {
.left_margin       = 46,
.right_margin   = 219,
.upper_margin   = 23,
.lower_margin   = 22,
.hsync_len  = 10,
.vsync_len  = 10,
.xres       = 800,
.yres       = 480,
},
.max_bpp    = 32,
.default_bpp    = 16,//这是16bpp

};

3.main()中
buffer =(char *)malloc(1152054); //不要小于bmp文件大小

运行:
[root@farsight /]# ./lcd_test /dev/fb0 logo_icer_800x480.bmp
pic_fd=3
len =1152054
xres =800
yres =480
screensize =768000
framebuffer_ptr is mmaped ok!
1
test picture!
loadjpeg00000!!!!
bmpread0000000!!!!
bm2fb1600000000000!!!!
2
length1 =23
length =23
length =23