LCD驱动程序

假设
app:  open("/dev/fb0", ...)   主设备号: 29, 次设备号: 0
--------------------------------------------------------------
kernel:
         fb_open
         	int fbidx = iminor(inode);
         	struct fb_info *info = = registered_fb[0];

app:  read()
---------------------------------------------------------------
kernel:
		fb_read
			int fbidx = iminor(inode);
			struct fb_info *info = registered_fb[fbidx];
			if (info->fbops->fb_read)
				return info->fbops->fb_read(info, buf, count, ppos);
         	
			src = (u32 __iomem *) (info->screen_base + p);
			dst = buffer;
			*dst++ = fb_readl(src++);
			copy_to_user(buf, buffer, c)         	

问1. registered_fb在哪里被设置？
答1. register_framebuffer

怎么写LCD驱动程序？
1. 分配一个fb_info结构体: framebuffer_alloc
2. 设置
3. 注册: register_framebuffer
4. 硬件相关的操作

测试：
1. make menuconfig去掉原来的驱动程序
-> Device Drivers
  -> Graphics support
<M> S3C2410 LCD framebuffer support

2. make uImage
   make modules  

3. 使用新的uImage启动开发板:

4. 
insmod cfbcopyarea.ko 
insmod cfbfillrect.ko 
insmod cfbimgblt.ko 
insmod lcd.ko

echo hello > /dev/tty1  // 可以在LCD上看见hello
cat lcd.ko > /dev/fb0   // 花屏

5. 修改 /etc/inittab
tty1::askfirst:-/bin/sh
用新内核重启开发板

insmod cfbcopyarea.ko 
insmod cfbfillrect.ko 
insmod cfbimgblt.ko 
insmod lcd.ko
insmod buttons.ko