【Linux高级驱动】LCD驱动框架分析-白红宇

【Linux高级驱动】LCD驱动框架分析

阅读量：5773 次

发布时间：2019-06-18

本文共 2173 字，大约阅读时间需要 7 分钟。

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) 
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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) 
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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; 