1.framebuffer接口层(fbmem.c)
功能:给用户提供接口
fbmem_init //入口函数/*1.申请主设备号,注册字符设备*/
register_chrdev(FB_MAJOR(29),"fb",&fb_fops)
/*2.创建一个设备类*/
fb_class = class_create(THIS_MODULE, "graphics");
static const struct file_operations fb_fops = {
.owner = THIS_MODULE,
.read = fb_read,
.write = fb_write,
.unlocked_ioctl = fb_ioctl,
#ifdef CONFIG_COMPAT
.compat_ioctl = fb_compat_ioctl,
#endif
.mmap = fb_mmap,
.open = fb_open,
.release = fb_release,
#ifdef HAVE_ARCH_FB_UNMAPPED_AREA
.get_unmapped_area = get_fb_unmapped_area,
#endif
#ifdef CONFIG_FB_DEFERRED_IO
.fsync = fb_deferred_io_fsync,
#endif
};
2.从应用层往下分析
open
app: open("/dev/xxx",xxx)===============================
vfs: sys_open
...
...
fbmem.c struct file_operations fb_fops
.open = fb_open,
/*1.获取此设备号*/
int fbidx = iminor(inode);
struct fb_info *info;
/*2.以此设备号为下标,从register_fb数组中取出fb_info结构体*/
info = registered_fb[fbidx];
file->private_data = info;
if (info->fbops->fb_open) {
res = info->fbops->fb_open(info,1);
ioctl
app: ioctl(fd,FBIOGET_VSCREENINFO,args)===========================================
vfs: sys_ioctl
...
...
fbmem.c struct file_operations fb_fops
.unlocked_ioctl = fb_ioctl,
/*1.获取此设备号*/
struct inode *inode = file->f_path.dentry->d_inode;
int fbidx = iminor(inode);
/*2.以此设备号为下标,从register_fb数组中取出fb_info结构体*/
struct fb_info *info = registered_fb[fbidx];
do_fb_ioctl(info, cmd, arg);
struct fb_var_screeninfo var; //表示可变参数
struct fb_fix_screeninfo fix; //表示固定参数
switch (cmd) {
case FBIOGET_VSCREENINFO:
if (!lock_fb_info(info))
return -ENODEV;
var = info->var; //取出fb_info中的可变参数
unlock_fb_info(info);
ret = copy_to_user(argp, &var, sizeof(var)) ? -EFAULT : 0;
break;
}
搜索registered_fb数组,看在哪里被设置了?
s3c_fb_probe(struct platform_device *pdev)...
...
for (win = 0; win < S3C_FB_MAX_WIN; win++) {
/*设置一个硬件窗口:一个窗口就是一个帧缓冲设备,一个帧缓冲设备用struct fb_info来描述*/
s3c_fb_probe_win //drivers\video\s3c-fb.c
/*构建fb_info:表示一个帧缓冲设备*/
/*设置fb_info*/
/*设置它的可变参数*/
/*设置它的固定参数*/
/*设置它的操作方法*/
/*注册一个fb_info结构体*/
register_framebuffer(struct fb_info *fb_info)
/*将fb_info加入数组项*/
registered_fb[i] = fb_info;
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