code:sgtty - ikarishinjieva/unixV6-code-analyze-chs GitHub Wiki

8194 /* Stuff common to stty and gtty.

8196 * device routine.

8197 * v is 0 for stty; the parameters are taken from u.u_arg\[].

8198 * c is non-zero for gtty and is the place in which the

8199 * device routines place their information.

8200 */

8201 sgtty(v)

8202 int *v;

8203 {

8204 register struct file *fp;

8205 register struct inode *ip;

8206 if ((fp = getf(u.u_ar0[R0])) == NULL)

8207 return;

根据传入的文件描述号找到其对应的file结构
若不能找到便直接返回

8208 ip = fp->f_inode;

8209 if ((ip->i_mode&IFMT) != IFCHR) {

8210 u.u_error = ENOTTY;

8211 return;

根据file结构找到对应的文件INODE

若该INODE不是字符设备装载INODE
抛出错误,错误代码:ENOTTY

8212 }

8213 (*cdevsw[ip->i_addr[0].d_major].d_sgtty)(ip->i_addr[0],v);

根据字符设备装载INODE找到设备号,并启动该设备的d_sgtty函数

比如klsgtty

8214 }

8215 /* ------------------------- */