LCD驱动程序

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
   S3C2410 LCD framebuffer support

2. make uImage
   make modules
   cp arch/arm/boot/uImage /work/nfs_root/uImage_nolcd

3. 使用新的uImage启动开发板:
   nfs 30000000 192.168.31.202:/work/nfs_root/uImage_nolcd
   bootm 30000000

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vi /etc/inittab
   tty1::askfirst:-/bin/sh
   用新内核重启开发板
   nfs 30000000 192.168.31.202:/work/nfs_root/uImage_nolcd
   bootm 30000000

mount -t nfs -o nolock,vers=2 192.168.31.202:/work/nfs_root/first_fs /mnt
cd /mnt/

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

在开发板上按ls 回车，液晶屏则列出所在目录的文件