hi yang,
在 2012年3月10日 下午10:37，yang gqyang hustgqyang@gmail.com 写道：
Thanks for your comment. Finally, i find out that i made a mistake. The uart(8250) have not been restore after resume, instead, it use the configuration got from boot. The uart have not been restored correctly, so that "ls" can not output result correctly resulting in it seems that the busybox can not work correctly. Now, i still have a question about the uart: why the "printk" can work correctly, but the "printf" not?
Before this, i believe that the "printk" work correctly, then the uart work ok. but now, i need more reconsidaration about the relation between the "printk", "printf" and "uart". Can anyone give me some suggestion? Any comment is welcome, thanks a lot.
printk use "struct console" driver, it doesn't depend on a device node for userspace. printf actaully depends on uart_driver and a /dev/ttySx device node, stdout and stderr are redirected to /dev/ttySx uart is just a hardware which can be a tty or kernel console output.
-barry