Lcd

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
   cp arch/arm/boot/uImage  /work/nfs_root/uImage_nolcd

   make modules 
   cp drives/video/cfb*.ko  /work/nfs_root/first_fs

3. 使用新的uImage启动开发板:
   root
   nfs 30000000 192.168.3.108:/work/nfs_root/uImage_nolcd
   bootm 30000000

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

echo hello > /dev/tty1
cat lcd.ko > /dev/fb0