问题
最近在做嵌入式文件体系时运用了如下的inittab文件：
#/etc/inittab
::sysinit:/etc/init.d/rcS
::respawn:-/bin/sh
s3c2410_serial0::askfirst:-/bin/sh
::ctrlaltdel:/sbin/reboot
::shutdown:/bin/umount -a -r
::sysinit:/etc/init.d/rcS
::respawn:-/bin/sh
s3c2410_serial0::askfirst:-/bin/sh
::ctrlaltdel:/sbin/reboot
::shutdown:/bin/umount -a -r
成果呈现了：/bin/sh: cant access tty; job control turned off
剖析
BusyBox经过体系控制台来做些作业, 假如咱们的shell发动在 /dev/console(5,1)上, tty_io.c 函数open中noctty就被设置成1,导致这个问题,详细原因还不知道。总归要发动在一个实在的串口就没有关系。
Job control will be turned off since your shell can not obtain a controlling terminal. This typically happens when you run your shell on /dev/console. The kernel will not provide a controlling terminal on the /dev/console device. Your should run your shell on a normal tty such as tty1 or ttyS0 and everything will work perfectly. If you REALLY want your shell to run on /dev/console, then you can hack your kernel (if you are into that sortof thing) by changing drivers/char/tty_io.c to change the lines where it sets "noctty = 1;" to instead set it to "0". I recommend you instead run your shell on a real console...
解决方法
能够经过BusyBox的init指定shell的设备, 留意, S3C2410上, 串口0是s3c2410_serial0。也就是说去掉::respawn:-/bin/sh就能够啦~~
串口称号
串口称号能够是s3c2410_serialx、ttySACx和ttySx等，但底层运用的是设备的主设备号和次设备号来定位详细设备的。所以不管是串口的称号是什么
，只需主设备号和次设备号对了就能够。此外，经过mdev生成设备节点时，串口的称号是s3c2410_serialx。
S3C2410的串口驱动文件drivers/serial/s3c2410.c中，有如下数据结构：
[plain] view plain copy
print?
- staticstructuart_drivers3c24xx_uart_drv={
- .owner=THIS_MODULE,
- .dev_name=”s3c2410_serial”,
- .nr=3,
- .cons=S3C24XX_SERIAL_CONSOLE,
- .driver_name=S3C24XX_SERIAL_NAME,
- .major=S3C24XX_SERIAL_MAJOR,//主设备号为204
- .minor=S3C24XX_SERIAL_MINOR,//次设备号为64，这指第1个串口；第2个为65
- };
经过这个结构体就能够确认串口设备的主设备号和次设备号。
