标签：for string mnt ... 指定 ddr ifconf 文件属性 address
目录
title: hotplug/mdev机制
date: 2019/1/9 19:35:14
toc: true
---
我们以前创建设备的时候，使用class_create来自动创建设备，是利用了mdev根据我们的提供的信息来创建设备节点
我们使用drv_class_dev来创建设备,具体的实例如下
drv_class = class_create(THIS_MODULE, "drv");
drv_class_dev = class_device_create(drv_class, NULL, MKDEV(major, 0), NULL, "xyz%d", minor);继续分析class_device_create,可以看到最后调用kobject_uevent_env来调用我们自己设置的辅助函数uevent_helper,可以在内核加入打印函数打印这个变量
drv_class = class_create(THIS_MODULE, "drv");
drv_class_dev = class_device_create(drv_class, NULL, MKDEV(major, 0), NULL, "xyz%d", minor);
class_device_register(class_dev);
class_device_initialize(class_dev);
class_device_add(class_dev);
//KOBJ_ADD = (__force kobject_action_t) 0x01, /* exclusive to core */
sysfs_create_link(&class_dev->kobj,&class_dev->dev->kobj, "device");
kobject_uevent(&class_dev->kobj, KOBJ_ADD);
// 设置环境变量后调用辅助函数
kobject_uevent_env(kobj, action, NULL)
{
action_string = action_to_string(action); //return "add";
/* environment index */
envp = kzalloc(NUM_ENVP * sizeof (char *), GFP_KERNEL);
/* environment values */
buffer = kmalloc(BUFFER_SIZE, GFP_KERNEL);
/* complete object path */
devpath = kobject_get_path(kobj, GFP_KERNEL);
/* event environemnt for helper process only */
envp[i++] = "HOME=/";
envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
// 先将指针scratch指向分配到的buffer
// 再赋值到envp 环境变量中
/* default keys */
scratch = buffer;
envp [i++] = scratch;
scratch += sprintf(scratch, "ACTION=%s", action_string) + 1;
envp [i++] = scratch;
scratch += sprintf (scratch, "DEVPATH=%s", devpath) + 1;
envp [i++] = scratch;
scratch += sprintf(scratch, "SUBSYSTEM=%s", subsystem) + 1;
for (j = 0; envp_ext && envp_ext[j]; j++)
envp[i++] = envp_ext[j];
...
//我们自己在这里加入打印函数,查看下环境变量和uevent_helper
printk("userhelp=%s\n",uevent_helper);
for (i=0;envp[i];i++) {
printk("envp[%d]=%s\n",i,envp[i]);
}
printk("argv[1]=%s\n",subsystem);
// 辅助函数,也就是我们自动创建设备的mdev
/* call uevent_helper, usually only enabled during early boot */
if (uevent_helper[0]) {
char *argv [3];
argv [0] = uevent_helper;
argv [1] = (char *)subsystem;
argv [2] = NULL;
call_usermodehelper (argv[0], argv, envp, 0);
}
}启动后加载一个驱动,打印如下,起始启动内核的时候也有许多的打印,userhelp=/sbin/hotplug
// filename =dri_src.c
major=register_chrdev(0, "drv_register", &drv_fops); // 注册, 告诉内核
drv_class = class_create(THIS_MODULE, "drv_class");
drv_class_dev = class_device_create(drv_class, NULL, MKDEV(major, 0), NULL, "xyz%d", minor);可以看到个信息包含了主次设备号,文件路径,模块的名字等,这里注意一下,当你修改了一个模块 a.ko 为 b.ko ,加载b.ko 后使用lsmod显示的依然是 a 模块,这里的信息也是 a 模块的
这里的argv[1]其实就是envp[4]也就是类名
# insmod dri_src.ko
userhelp=/sbin/mdev
envp[0]=HOME=/
envp[1]=PATH=/sbin:/bin:/usr/sbin:/usr/bin
envp[2]=ACTION=add
envp[3]=DEVPATH=/module/dri_src #模块名,一般就是文件名,但这个文件名指的是当时编译好的名字,也就是C文件的名字,生成ko后修改名字无效
envp[4]=SUBSYSTEM=module
envp[5]=SEQNUM=754
argv[1]=module
userhelp=/sbin/mdev
envp[0]=HOME=/
envp[1]=PATH=/sbin:/bin:/usr/sbin:/usr/bin
envp[2]=ACTION=add
envp[3]=DEVPATH=/class/drv_class/xyz0 #设备文件的描述,最终会生成文件 /dev/xyz0
#输入子系统这里是 envp[3]=DEVPATH=/class/input/input1/event1
envp[4]=SUBSYSTEM=drv_class #类的名字 class_create创建,如果是输入子系统这里是
# envp[4]=SUBSYSTEM=input
envp[5]=SEQNUM=755
envp[6]=MAJOR=252
envp[7]=MINOR=0
argv[1]=drv_class #就是类名
# rmmod dri_src #卸载模块的时候使用ACTION=remove
userhelp=/sbin/mdev
envp[0]=HOME=/
envp[1]=PATH=/sbin:/bin:/usr/sbin:/usr/bin
envp[2]=ACTION=remove
envp[3]=DEVPATH=/class/drv_class/xyz0
envp[4]=SUBSYSTEM=drv_class
envp[5]=SEQNUM=756
envp[6]=MAJOR=252
envp[7]=MINOR=0
userhelp=/sbin/mdev
envp[0]=HOME=/
envp[1]=PATH=/sbin:/bin:/usr/sbin:/usr/bin
envp[2]=ACTION=remove
envp[3]=DEVPATH=/class/drv_class
envp[4]=SUBSYSTEM=class
envp[5]=SEQNUM=757
userhelp=/sbin/mdev
envp[0]=HOME=/
envp[1]=PATH=/sbin:/bin:/usr/sbin:/usr/bin
envp[2]=ACTION=remove
envp[3]=DEVPATH=/module/dri_src
envp[4]=SUBSYSTEM=module
envp[5]=SEQNUM=758
接下来就去执行函数/sbin/mdev,也就是busybox的应用程序,定义在busybox-1.7.0\util-linux\mdev.c
匹配后执行make_device(temp, 0);,getenv是个库函数,我们之前在kobject_uevent_env设置了参数
mdev_main(int argc, char **argv)
//扫描模式,一般是上电用的
scan
//我们自己实际用的
action = getenv("ACTION");
env_path = getenv("DEVPATH");
sprintf(temp, "/sys%s", env_path);
if (!strcmp(action, "remove"))
make_device(temp, 1);
else if (!strcmp(action, "add")) {
make_device(temp, 0);
kernel 传递的DEVPATH是envp[3]=DEVPATH=/class/drv_class/xyz0,也就是参数实际是/sys/class/drv_class/xyz0
/sys/class/drv_class/xyz0/dev是否存在 这个文件包含了主次设备号// 先判断是否设备文件已经存在,也就是判断 /sys/class/drv_class/xyz0/dev是否存在 这个文件包含了主次设备号
//# cat /sys/class/drv_class/xyz0/dev
//252:0
// strcat 拼接字符串
if (!delete) {
strcat(path, "/dev");
len = open_read_close(path, temp + 1, 64);
*temp++ = 0;
if (len < 1) return;
}class的c字符,就判断是字符设备了 /// sys/class/drv_class/xyz0
device_name = bb_basename(path);
//bb_basename 从前往后找到最后一个"/",这里就是找到文件名
type = path[5]==‘c‘ ? S_IFCHR : S_IFBLK; if (ENABLE_FEATURE_MDEV_CONF)
{
fd = open("/etc/mdev.conf", O_RDONLY);
} if (!delete) {
// 从设备文件的描述读取主次设备号 /sys/class/drv_class/xyz0/dev
if (sscanf(temp, "%d:%d", &major, &minor) != 2) return;
// mknod 创建设备文件 type=c 就是字符设备 makedev 包含了主次设备号
if (mknod(device_name, mode | type, makedev(major, minor)) && errno != EEXIST)
if (major == root_major && minor == root_minor)
symlink(device_name, "root");
// 如果有配置文件,还需要手动更改设备文件属性
if (ENABLE_FEATURE_MDEV_CONF) chown(device_name, uid, gid);
}ENABLE_FEATURE_MDEV_CONF,在make menuconfig 搜索mdev,可以看到已经启用了│ -> Linux System Utilities │
│ -> mdev (MDEV [=y]) │
│ -> Support /etc/mdev.conf (FEATURE_MDEV_CONF [=y]) 如何使用这个配置文件去自动创建设备文件? 我们搜索文档busybox-1.7.0/docs/mdev.txt查看如下格式,也就是发现设备文件(前/后)来执行命令
The file has the format:
<device regex> <uid>:<gid> <octal permissions>
For example:
hd[a-z][0-9]* 0:3 660
<device regex> <uid>:<gid> <octal permissions> [<@|$|*> <command>]
The special characters have the meaning:
@ Run after creating the device.
$ Run before removing the device.
* Run both after creating and before removing the device.
device regex：正则表达式，表示哪一个设备
uid: owner
gid: 组ID
octal permissions：以八进制表示的属性
用户组 读写执行+读写执行+读写执行 110+110+000=660=crwcrw---
@：创建设备节点之后执行命令
$：删除设备节点之前执行命令
*: 创建设备节点之后 和 删除设备节点之前 执行命令
command：要执行的命令存在这样一个驱动,自动创建4个设备文件,代码仓库的4th
for (minor = 0; minor < 4; minor++)
{
firstdrv_class_dev[minor] = class_device_create(firstdrv_class, NULL, MKDEV(major, minor), NULL, "xyz%d", minor);
}自动创建设备如下
# ls /dev/xyz* -l
crw-rw---- 1 0 0 252, 0 Jan 4 07:13 /dev/xyz0
crw-rw---- 1 0 0 252, 1 Jan 4 07:13 /dev/xyz1
crw-rw---- 1 0 0 252, 2 Jan 4 07:13 /dev/xyz2
crw-rw---- 1 0 0 252, 3 Jan 4 07:13 /dev/xyz3使用字符全匹配,更改权限为777,先卸载驱动
# vi /etc/mdev.conf
xyz0 0:0 777
xyz1 0:0 777
xyz2 0:0 777
# ls /dev/xyz* -l
crwxrwxrwx 1 0 0 252, 0 Jan 4 07:21 /dev/xyz0
crwxrwxrwx 1 0 0 252, 1 Jan 4 07:21 /dev/xyz1
crwxrwxrwx 1 0 0 252, 2 Jan 4 07:21 /dev/xyz2
crw-rw---- 1 0 0 252, 3 Jan 4 07:21 /dev/xyz3使用正则匹配
# vi /etc/mdev.conf
xyz[0123]? 0:0 777
# ls /dev/xyz* -l
crwxrwxrwx 1 0 0 252, 0 Jan 4 07:25 /dev/xyz0
crwxrwxrwx 1 0 0 252, 1 Jan 4 07:25 /dev/xyz1
crwxrwxrwx 1 0 0 252, 2 Jan 4 07:25 /dev/xyz2
crwxrwxrwx 1 0 0 252, 3 Jan 4 07:25 /dev/xyz3
这里使用@表示在创建设备节点后执行命令
# vi /etc/mdev.conf
xyz[0123]? 0:0 777 @ echo create /dev/$MDEV > /dev/console
insmod dri.ko
# create /dev/xyz2
create /dev/xyz3
create /dev/xyz0
create /dev/xyz1# vi /etc/mdev.conf
xyz[0123]? 0:0 777 $ echo del /dev/$MDEV > /dev/console
insmod dri.ko
# del /dev/xyz2
del /dev/xyz3
del /dev/xyz0
del /dev/xyz1注意 在$ACTION前有个空格,不能少
# cat /etc/mdev.conf
xyz[0123]? 0:0 777 * if [ $ACTION = "add" ];then echo create /dev/$MDEV > /dev/console; else echo del /dev/$MDEV > dev/console ;fi
#insmod dri_4th.ko
# create /dev/xyz2
create /dev/xyz3
create /dev/xyz0
create /dev/xyz1
#rmmod dri
del /dev/xyz1
del /dev/xyz0
del /dev/xyz2
del /dev/xyz3创建一个脚本文件mdev.sh,放到一个指定的目录,加入执行权限hmod +x /mnt/mdev.sh
#!/bin/sh
if [ $ACTION = "add" ];
then
echo create /dev/$MDEV > /dev/console;
else
echo remove /dev/$MDEV > /dev/console;
fi修改配置文件
# chmod +x /mnt/mdev.sh
# cat /etc/mdev.conf
xyz[0123]? 0:0 777 * /mnt/mdev.sh然后会和上面同样的结果
usb 1-1: new full speed USB device using s3c2410-ohci and address 3
usb 1-1: configuration #1 chosen from 1 choice
scsi1 : SCSI emulation for USB Mass Storage devices
sd 1:0:0:0: [sda] 60555264 512-byte hardware sectors (31004 MB)
sd 1:0:0:0: [sda] Write Protect is off
sd 1:0:0:0: [sda] Assuming drive cache: write through
sd 1:0:0:0: [sda] 60555264 512-byte hardware sectors (31004 MB)
sd 1:0:0:0: [sda] Write Protect is off
sd 1:0:0:0: [sda] Assuming drive cache: write through
sda: sda1 sda2查看下U盘设备,这个u盘有两个分区,一个是PE,所以sda1是第一个分区,sda2是第二个分区
# ls -l /dev/sda*
brw-rw---- 1 0 0 8, 0 Jan 4 06:57 /dev/sda
brw-rw---- 1 0 0 8, 1 Jan 4 06:57 /dev/sda1
brw-rw---- 1 0 0 8, 2 Jan 4 06:57 /dev/sda2 mount /dev/sda1 /mnt创建文件,加入配置文件vi /etc/mdev.conf
sda[1-9]+ 0:0 660 * if [ $ACTION = "add" ]; then mount /dev/$MDEV /mnt; else umount /mnt; fi0:0 uid,默认为0就好了660权限*,创建设备节点之后 和 删除设备节点之前 执行命令/dev/$MDEV,表示要创建/注销的那个设备节点或者使用脚本mdev.sh,更好看
#!/bin/sh
if [ $ACTION = "add" ];
then
mount /dev/$MDEV /mnt;
else
umount /mnt;
fiifconfig eth0 192.168.95.200
mount -t nfs -o nolock,vers=2 192.168.95.222:/home/book/stu /mnt
使用nfs在uboot下下载内核
nfs 30000000 12.16.45.222:/uimage
bootm 30000000输入env可以查看当前shell的环境变量
# env
USER=root
OLDPWD=/etc
HOME=/
TERM=vt102
PATH=/sbin:/usr/sbin:/bin:/usr/bin
SHELL=/bin/sh
PWD=/mnt
# env
USER=root
OLDPWD=/mnt
HOME=/
TERM=vt102
PATH=/sbin:/usr/sbin:/bin:/usr/bin
SHELL=/bin/sh
PWD=/
# usb 1-1: new full speed USB device using s3c2410-ohci and address 3
userhelp=/sbin/mdev
envp[0]=HOME=/
envp[1]=PATH=/sbin:/bin:/usr/sbin:/usr/bin
envp[2]=ACTION=add
envp[3]=DEVPATH=/devices/platform/s3c2410-ohci/usb1/1-1
envp[4]=SUBSYSTEM=usb
envp[5]=SEQNUM=761
envp[6]=MAJOR=189
envp[7]=MINOR=2
envp[8]=DEVTYPE=usb_device
envp[9]=PHYSDEVBUS=usb
envp[10]=DEVICE=/proc/bus/usb/001/003
envp[11]=PRODUCT=951/1666/100
envp[12]=TYPE=0/0/0
envp[13]=BUSNUM=001
envp[14]=DEVNUM=003
argv[1]=usb
userhelp=/sbin/mdev
envp[0]=HOME=/
envp[1]=PATH=/sbin:/bin:/usr/sbin:/usr/bin
envp[2]=ACTION=add
envp[3]=DEVPATH=/class/usb_endpoint/usbdev1.3_ep00
envp[4]=SUBSYSTEM=usb_endpoint
envp[5]=SEQNUM=762
envp[6]=MAJOR=253
envp[7]=MINOR=2
envp[8]=PHYSDEVPATH=/devices/platform/s3c2410-ohci/usb1/1-1
envp[9]=PHYSDEVBUS=usb
envp[10]=PHYSDEVDRIVER=usb
argv[1]=usb_endpoint
usb 1-1: configuration #1 chosen from 1 choice
userhelp=/sbin/mdev
envp[0]=HOME=/
envp[1]=PATH=/sbin:/bin:/usr/sbin:/usr/bin
envp[2]=ACTION=add
envp[3]=DEVPATH=/devices/platform/s3c2410-ohci/usb1/1-1/1-1:1.0
envp[4]=SUBSYSTEM=usb
envp[5]=SEQNUM=763
envp[6]=DEVTYPE=usb_interface
envp[7]=PHYSDEVBUS=usb
envp[8]=DEVICE=/proc/bus/usb/001/003
envp[9]=PRODUCT=951/1666/100
envp[10]=TYPE=0/0/0
envp[11]=INTERFACE=8/6/80
envp[12]=MODALIAS=usb:v0951p1666d0100dc00dsc00dp00ic08isc06ip50
argv[1]=usb
scsi1 : SCSI emulation for USB Mass Storage devices
userhelp=/sbin/mdev
envp[0]=HOME=/
envp[1]=PATH=/sbin:/bin:/usr/sbin:/usr/bin
envp[2]=ACTION=add
envp[3]=DEVPATH=/class/scsi_host/host1
envp[4]=SUBSYSTEM=scsi_host
envp[5]=SEQNUM=764
envp[6]=PHYSDEVPATH=/devices/platform/s3c2410-ohci/usb1/1-1/1-1:1.0/host1
argv[1]=scsi_host
userhelp=/sbin/mdev
envp[0]=HOME=/
envp[1]=PATH=/sbin:/bin:/usr/sbin:/usr/bin
envp[2]=ACTION=add
envp[3]=DEVPATH=/class/usb_endpoint/usbdev1.3_ep81
envp[4]=SUBSYSTEM=usb_endpoint
envp[5]=SEQNUM=765
envp[6]=MAJOR=253
envp[7]=MINOR=3
envp[8]=PHYSDEVPATH=/devices/platform/s3c2410-ohci/usb1/1-1/1-1:1.0
envp[9]=PHYSDEVBUS=usb
envp[10]=PHYSDEVDRIVER=usb-storage
argv[1]=usb_endpoint
userhelp=/sbin/mdev
envp[0]=HOME=/
envp[1]=PATH=/sbin:/bin:/usr/sbin:/usr/bin
envp[2]=ACTION=add
envp[3]=DEVPATH=/class/usb_endpoint/usbdev1.3_ep02
envp[4]=SUBSYSTEM=usb_endpoint
envp[5]=SEQNUM=766
envp[6]=MAJOR=253
envp[7]=MINOR=4
envp[8]=PHYSDEVPATH=/devices/platform/s3c2410-ohci/usb1/1-1/1-1:1.0
envp[9]=PHYSDEVBUS=usb
envp[10]=PHYSDEVDRIVER=usb-storage
argv[1]=usb_endpoint
scsi 1:0:0:0: Direct-Access Kingston DataTraveler 3.0 PMAP PQ: 0 ANSI: 6
userhelp=/sbin/mdev
envp[0]=HOME=/
envp[1]=PATH=/sbin:/bin:/usr/sbin:/usr/bin
envp[2]=ACTION=add
envp[3]=DEVPATH=/devices/platform/s3c2410-ohci/usb1/1-1/1-1:1.0/host1/target1:0:0/1:0:0:0
envp[4]=SUBSYSTEM=scsi
envp[5]=SEQNUM=767
envp[6]=PHYSDEVBUS=scsi
envp[7]=MODALIAS=scsi:t-0x00
argv[1]=scsi
userhelp=/sbin/mdev
envp[0]=HOME=/
envp[1]=PATH=/sbin:/bin:/usr/sbin:/usr/bin
envp[2]=ACTION=add
envp[3]=DEVPATH=/class/scsi_disk/1:0:0:0
envp[4]=SUBSYSTEM=scsi_disk
envp[5]=SEQNUM=768
envp[6]=PHYSDEVPATH=/devices/platform/s3c2410-ohci/usb1/1-1/1-1:1.0/host1/target1:0:0/1:0:0:0
envp[7]=PHYSDEVBUS=scsi
envp[8]=PHYSDEVDRIVER=sd
argv[1]=scsi_disk
sd 1:0:0:0: [sda] 60555264 512-byte hardware sectors (31004 MB)
sd 1:0:0:0: [sda] Write Protect is off
sd 1:0:0:0: [sda] Assuming drive cache: write through
sd 1:0:0:0: [sda] 60555264 512-byte hardware sectors (31004 MB)
sd 1:0:0:0: [sda] Write Protect is off
sd 1:0:0:0: [sda] Assuming drive cache: write through
sda: sda1 sda2
userhelp=/sbin/mdev
envp[0]=HOME=/
envp[1]=PATH=/sbin:/bin:/usr/sbin:/usr/bin
envp[2]=ACTION=add
envp[3]=DEVPATH=/block/sda
envp[4]=SUBSYSTEM=block
envp[5]=SEQNUM=769
envp[6]=MINOR=0
envp[7]=MAJOR=8
envp[8]=PHYSDEVPATH=/devices/platform/s3c2410-ohci/usb1/1-1/1-1:1.0/host1/target1:0:0/1:0:0:0
envp[9]=PHYSDEVBUS=scsi
envp[10]=PHYSDEVDRIVER=sd
argv[1]=block
userhelp=/sbin/mdev
envp[0]=HOME=/
envp[1]=PATH=/sbin:/bin:/usr/sbin:/usr/bin
envp[2]=ACTION=add
envp[3]=DEVPATH=/block/sda/sda1
envp[4]=SUBSYSTEM=block
envp[5]=SEQNUM=770
envp[6]=MINOR=1
envp[7]=MAJOR=8
envp[8]=PHYSDEVPATH=/devices/platform/s3c2410-ohci/usb1/1-1/1-1:1.0/host1/target1:0:0/1:0:0:0
envp[9]=PHYSDEVBUS=scsi
envp[10]=PHYSDEVDRIVER=sd
argv[1]=block
userhelp=/sbin/mdev
envp[0]=HOME=/
envp[1]=PATH=/sbin:/bin:/usr/sbin:/usr/bin
envp[2]=ACTION=add
envp[3]=DEVPATH=/block/sda/sda2
envp[4]=SUBSYSTEM=block
envp[5]=SEQNUM=771
envp[6]=MINOR=2
envp[7]=MAJOR=8
envp[8]=PHYSDEVPATH=/devices/platform/s3c2410-ohci/usb1/1-1/1-1:1.0/host1/target1:0:0/1:0:0:0
envp[9]=PHYSDEVBUS=scsi
envp[10]=PHYSDEVDRIVER=sd
argv[1]=block
sd 1:0:0:0: [sda] Attached SCSI removable disk
userhelp=/sbin/mdev
envp[0]=HOME=/
envp[1]=PATH=/sbin:/bin:/usr/sbin:/usr/bin
envp[2]=ACTION=add
envp[3]=DEVPATH=/class/scsi_device/1:0:0:0
envp[4]=SUBSYSTEM=scsi_device
envp[5]=SEQNUM=772
envp[6]=PHYSDEVPATH=/devices/platform/s3c2410-ohci/usb1/1-1/1-1:1.0/host1/target1:0:0/1:0:0:0
envp[7]=PHYSDEVBUS=scsi
envp[8]=PHYSDEVDRIVER=sd
argv[1]=scsi_device
标签：for string mnt ... 指定 ddr ifconf 文件属性 address
原文地址：https://www.cnblogs.com/zongzi10010/p/10246447.html
