修改串口节点名称

需求：3368的老主板更换为3568的新主板，为了app兼容两款主板，要求串口号一致。有个ttyS0的口，需要对应改为ttySWK0

　　跟踪驱动代码：

dw8250_probe(drivers\tty\serial\8250\8250_dw.c)
        -->serial8250_register_8250_port(drivers\tty\serial\8250\8250_core.c)
            -->uart_add_one_port(drivers\tty\serial\serial_core.c)
                -->tty_port_register_device_attr_serdev(drivers\tty\tty_port.c)
                    -->tty_register_device_attr
                        -->tty_line_name(drivers\tty\tty_io.c)

tty_line_name函数：

1 static ssize_t tty_line_name(struct tty_driver *driver, int index, char *p)
2         {
3             if (driver->flags & TTY_DRIVER_UNNUMBERED_NODE)
4                 return sprintf(p, "%s", driver->name);
5             else
6                 return sprintf(p, "%s%d", driver->name,
7                            index + driver->name_base);
8                 
9         }

可知ttySx串口节点设备名称是由驱动名称 driver->name和串口序号index 组成的。

这里做一个判断，index是0，串口节点设备名称则为ttySWK0即可满足需求：

 1 diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
 2         index b6f42d0ee626..fb6750ad356d 100644
 3         --- a/drivers/tty/tty_io.c
 4         +++ b/drivers/tty/tty_io.c
 5         @@ -1135,9 +1135,14 @@ static ssize_t tty_line_name(struct tty_driver *driver, int index, char *p)
 6          {
 7                 if (driver->flags & TTY_DRIVER_UNNUMBERED_NODE)
 8                         return sprintf(p, "%s", driver->name);
 9         -       else
10         +       else{
11         +               if(index == 0){
12         +                       return sprintf(p, "ttySWK%d",index);
13         +               }else
14                         return sprintf(p, "%s%d", driver->name,
15                                        index + driver->name_base);
16         +       }
17         +               
18          }

　编译好重新烧录，ttyS改为ttySWK0：

 设置串口权限：

/device/rockchip/common
diff --git a/ueventd.rockchip.rc b/ueventd.rockchip.rc
index f16524a..9408538 100755
--- a/ueventd.rockchip.rc
+++ b/ueventd.rockchip.rc
@@ -75,6 +75,7 @@
 /dev/ttyS7                0666   root  root
 /dev/ttyS8                0666   root  root
 /dev/ttyS9                0666   root  root
+/dev/ttySWK0              0666   root  root

参考：

https://www.jianshu.com/p/c345576b94a1?ivk_sa=1024320u
https://www.ngui.cc/article/show-884649.html?action=onClick