DEVT（devt币为什么会大跌）

2023年05月29日 08:47

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很多朋友在找时都会咨询DEVT和devt币为什么会大跌，这说明有一部分人对这个问题不太了解，您了解吗？那么什么是devt币为什么会大跌？下面就由小编带大家详细了解一下吧！

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不是。

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The Career Planning Process

Taking It Step-By-Step

By Dawn Rosenberg McKay, About.com

What is Career Planning?

Career planning is a lifelong process, which includes choosing an occupation, getting a job, growing in our job, possibly changing careers, and eventually retiring. The Career Planning Site offers coverage of all these areas. This article will focus on career choice and the process one goes through in selecting an occupation. This may happen once in our lifetimes, but it is more likely to happen several times as we first define and then redefine ourselves and our goals.

Career Planning: A Four Step Process

The career planning process is comprised of four steps. One might seek the services of a career development professional to help facilitate his or her journey through this process. Whether or not you choose to work with a professional, or work through the process on your own is less important than the amount of thought and energy you put into choosing a career.

Self

Gather information about yourself (self assessment)

* Interests

* Values

* Roles

* Skills/Aptitudes

* Preferred Environments

* Developmental Needs

* Your realities

Options

* Explore the occupations in which you are interested

* Research the industries in which you would like to work

* Research the Labor Market

Get more specific information after you narrow down your options by:

* Job Shadowing

* Part time work, internships, or volunteer opportunities

* Written materials

* Informational interviews

Match

During this phase of the process, you will:

* Identify possible occupations

* Evaluate these occupations

* Explore alternatives

* Choose both a short term and a long term option

Action

You will develop the steps you need to take in order to reach your goal, for example:

* Investigating sources of additional training and education, if needed

* Developing a job search strategy

* Writing your resume

* Gathering company information

* Composing cover letters

* Preparing for job interviews

Using Your Network

Thursday September 25, 2008

Many people think about networking only when it comes to a job search. The saying “it’s not what you know, it’s who you know” usually refers to using your connections to get a job or to move up the corporate ladder. Smart people, though, use their network in many other ways.

Take for example a colleague of mine who needed some information about the pre-teen and teen phenomenon, High School Musical. Having no children that age herself, she was not well-acquainted with this series of television movies, an upcoming feature film and a gizillion licensed products (some of us know a little too much about it). I guess she could have done some research and found information on the Web. There is certainly plenty — a Google search yields 66,500,000 hits. Smart as my colleague is, she knew she could do better than that. Why should she have to sift through all that stuff, much of it irrelevant, when she could go directly to the source — the actual fans.

So, my colleague went to her network to find out if any of us have kids who are High School Musical fans. She hit the jackpot and got many responses to her request. Several of us had kids who are fans of HSM, as it is known to its target audience. She was able to ask them some very focused questions in order to get just what she needed. What a great example of using your network for something other than job searching.

字符设备驱动程序框架 1、写出open、write函数 2、告诉内核 1）、定义一个struct file_operations结构并填充好 static struct file_operations first_drv_fops = { .owner = THIS_MODULE, /* 这是一个宏，推向编译模块时自动创建的__this_module变量 */ .open = first_drv_open, .write = first_drv_write, }; 2）、把struct file_operations结构体告诉内核 major = register_chrdev(0, “first_drv”, first_drv_fops); // 注册, 告诉内核相关参数：第一个，设备号，0自动分配主设备号，否则为主设备号0－255 第二个：设备名第二个：struct file_operations结构体 4）、register_chrdev由谁调用（入口函数调用） static int first_drv_init(void) 5）、入口函数须使用内核宏来修饰 module_init(first_drv_init); module_init会定义一个结构体，这个结构体里面有一个函数指针指向first_drv_init这个函数，当我们加载或安装一个驱动时，内核会自动找到这个结构体，然后调用里面的函数指针，这个函数指针指向first_drv_init这个函数，first_drv_init这个函数就是把struct file_operations结构体告诉内核 6）、有入口函数就有出口函数 module_exit(first_drv_exit); 最后加上协议 MODULE_LICENSE(“GPL”); 3、mdev根据系统信息自动创建设备节点：每次写驱动都要手动创建设备文件过于麻烦，使用设备管理文件系统则方便很多。在2.6的内核以前一直使用的是devfs，但是它存在许多缺陷。它创建了大量的设备文件，其实这些设备更本不存在。而且设备与设备文件的映射具有不确定性，比如U盘即可能对应sda，又可能对应sdb。没有足够的主/辅设备号。2.6之后的内核引入了sysfs文件系统，它挂载在/sys上，配合udev使用，可以很好的完成devfs的功能，并弥补了那些缺点。（这里说一下，当今内核已经使用netlink了）。 udev是用户空间的一个应用程序，在嵌入式中用的是mdev，mdev在busybox中。mdev是udev的精简版。首先在busybox中添加支持mdev的选项： Linux System Utilities — [*] mdev [*] Support /etc/mdev.conf [*] Support subdirs/symlinks [*] Support regular expressions substitutions when renaming device [*] Support command execution at device addition/removal 然后修改/etc/init.d/rcS: echo /sbin/mdev /proc/sys/kernel/hotplug /sbin/mdev -s 执行mdev -s ：以‘-s’为参数调用位于 /sbin目录写的mdev（其实是个链接，作用是传递参数给/bin目录下的busybox程序并调用它），mdev扫描 /sys/class 和 /sys/block 中所有的类设备目录，如果在目录中含有名为“dev”的文件，且文件中包含的是设备号，则mdev就利用这些信息为这个设备在/dev 下创建设备节点文件。一般只在启动时才执行一次 “mdev -s”。热插拔事件：由于启动时运行了命令：echo /sbin/mdev /proc/sys/kernel/hotplug ，那么当有热插拔事件产生时，内核就会调用位于 /sbin目录的mdev。这时mdev通过环境变量中的 ACTION 和 DEVPATH，来确定此次热插拔事件的动作以及影响了/sys中的那个目录。接着会看看这个目录中是否“dev”的属性文件，如果有就利用这些信息为这个设备在/dev 下创建设备节点文件重新打包文件系统，这样/sys目录，/dev目录就有东西了下面是create_class的原型： #define class_create(owner, name) / ({ / static struct lock_class_key __key; / __class_create(owner, name, __key); / }) extern struct class * __must_check __class_create(struct module *owner, const char *name, struct lock_class_key *key); class_destroy的原型如下： extern void class_destroy(struct class *cls); device_create的原型如下： extern struct device *device_create(struct class *cls, struct device *parent, dev_t devt, void *drvdata, const char *fmt, …) __attribute__((format(printf, 5, 6))); device_destroy的原型如下： extern void device_destroy(struct class *cls, dev_t devt); 具体使用如下，可参考后面的实例： static struct class *firstdrv_class; static struct class_device *firstdrv_class_dev; firstdrv_class = class_create(THIS_MODULE, “firstdrv”); firstdrv_class_dev = class_device_create(firstdrv_class, NULL, MKDEV(major, 0), NULL, “xyz”); /* /dev/xyz */ class_device_unregister(firstdrv_class_dev); class_destroy(firstdrv_class); 下面再来看一下应用程序如何找到这个结构体的在应用程序中我们使用open打开一个设备：如：open(/dev/xxx, O_RDWR); xxx有一个属性，如字符设备为c,后面为读写权限，还有主设备名、次设备名，我们注册时通过register_chrdev(0, “first_drv”, first_drv_fops)（有主设备号，设备名，struct file_operations结构体）将first_drv_fops结构体注册到内核数组chrdev中去的，结构体中有open,write函数，那么应用程序如何找到它的，事实上是根据打开的这个文件的属性中的设备类型及主设备号在内核数组chrdev里面找到我们注册的first_drv_fops，实例代码： #include #include #include #include #include #include #include #include #include #include static struct class *firstdrv_class; static struct class_device *firstdrv_class_dev; volatile unsigned long *gpfcon = NULL; volatile unsigned long *gpfdat = NULL; static int first_drv_open(struct inode *inode, struct file *file) { //printk(“first_drv_open

“); /* 配置GPF4,5,6为输出 */ *gpfcon = ~((0x3(4*2)) | (0x3(5*2)) | (0x3(6*2))); *gpfcon |= ((0x1(4*2)) | (0x1(5*2)) | (0x1(6*2))); return 0; } static ssize_t first_drv_write(struct file *file, const char __user *buf, size_t count, loff_t * ppos) { int val; //printk(“first_drv_write

“); copy_from_user(val, buf, count); // copy_to_user(); if (val == 1) { // 点灯 *gpfdat = ~((14) | (15) | (16)); } else { // 灭灯 *gpfdat |= (14) | (15) | (16); } return 0; } static struct file_operations first_drv_fops = { .owner = THIS_MODULE, /* 这是一个宏，推向编译模块时自动创建的__this_module变量 */ .open = first_drv_open, .write = first_drv_write, }; int major; static int first_drv_init(void) { major = register_chrdev(0, “first_drv”, first_drv_fops); // 注册, 告诉内核 firstdrv_class = class_create(THIS_MODULE, “firstdrv”); firstdrv_class_dev = class_device_create(firstdrv_class, NULL, MKDEV(major, 0), NULL, “xyz”); /* /dev/xyz */ gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16); gpfdat = gpfcon + 1; return 0; } static void first_drv_exit(void) { unregister_chrdev(major, “first_drv”); // 卸载 class_device_unregister(firstdrv_class_dev); class_destroy(firstdrv_class); iounmap(gpfcon); } module_init(first_drv_init); module_exit(first_drv_exit); MODULE_LICENSE(“GPL”); 编译用Makefile文件 KERN_DIR = /work/system/linux-2.6.22.6 all: make -C $(KERN_DIR) M=`pwd` modules clean: make -C $(KERN_DIR) M=`pwd` modules clean rm -rf modules.order obj-m += first_drv.o 测试程序： #include #include #include #include /* firstdrvtest on * firstdrvtest off */ int main(int argc, char **argv) { int fd; int val = 1; fd = open(“/dev/xyz”, O_RDWR); if (fd 0) { printf(“can’t open!

“); } if (argc != 2) { printf(“Usage :

“); printf(“%s

“, argv[0]); return 0; } if (strcmp(argv[1], “on”) == 0) { val = 1; } else { val = 0; } write(fd, val, 4); return 0; }

DEVT的数量取决于持有者的地址数量、DEVT的价格以及质押智能合约的发布日期。从合约发布的第一天起，DEVT最低质押数将线性缓慢增加。

OKEx代币OKB的持有者将能够通过质押OKB来赚取DEVT。

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Linux下生成驱动设备节点文件的方法有3个：1、手动mknod；2、利用devfs；3、利用udev

在刚开始写Linux设备驱动程序的时候，很多时候都是利用mknod命令手动创建设备节点，实际上Linux内核为我们提供了一组函数，可以用来在模块加载的时候自动在/dev目录下创建相应设备节点，并在卸载模块时删除该节点。

在2.6.17以前，在/dev目录下生成设备文件很容易，

devfs_mk_bdev

devfs_mk_cdev

devfs_mk_symlink

devfs_mk_dir

devfs_remove

这几个是纯devfs的api，2.6.17以前可用，但后来devfs被sysfs+udev的形式取代，同时期sysfs文件系统可以用的api：

class_device_create_file，在2.6.26以后也不行了，现在，使用的是device_create ，从2.6.18开始可用

struct device *device_create(struct class *class, struct device *parent,

dev_t devt, const char *fmt, …)

从2.6.26起又多了一个参数drvdata： the data to be added to the device for callbacks

不会用可以给此参数赋NULL

struct device *device_create(struct class *class, struct device *parent,

dev_t devt, void *drvdata, const char *fmt, …)

下面着重讲解第三种方法udev

在驱动用加入对udev的支持主要做的就是：在驱动初始化的代码里调用class_create(…)为该设备创建一个class，再为每个设备调用device_create(…)( 在2.6较早的内核中用class_device_create)创建对应的设备。

内核中定义的struct class结构体，顾名思义，一个struct class结构体类型变量对应一个类，内核同时提供了class_create(…)函数，可以用它来创建一个类，这个类存放于sysfs下面，一旦创建好了这个类，再调用 device_create(…)函数来在/dev目录下创建相应的设备节点。这样，加载模块的时候，用户空间中的udev会自动响应 device_create(…)函数，去/sysfs下寻找对应的类从而创建设备节点。

struct class和class_create(…) 以及device_create(…)都包含在在/include/linux/device.h中，使用的时候一定要包含这个头文件，否则编译器会报错。

struct class定义在头文件include/linux/device.h中

class_create(…)在/drivers/base/class.c中实现

device_create(…)函数在/drivers/base/core.c中实现

class_destroy(…),device_destroy(…)也在/drivers/base/core.c中实现调用过程类似如下：

static struct class *spidev_class;

/*————————————————————————-*/

static int __devinit spidev_probe(struct spi_device *spi)

{

….

dev =device_create(spidev_class, spi-dev, spidev-devt,

spidev, “spidev%d.%d”,

spi-master-bus_num, spi-chip_select);

…

}

static int __devexit spidev_remove(struct spi_device *spi)

{

……

device_destroy(spidev_class, spidev-devt);

…..

return 0;

}

static struct spi_driver spidev_spi = {

.driver = {

.name = “spidev”,

.owner = THIS_MODULE,

.probe = spidev_probe,

.remove = __devexit_p(spidev_remove),

};

/*————————————————————————-*/

static int __init spidev_init(void)

{

….

spidev_class =class_create(THIS_MODULE, “spidev”);

if (IS_ERR(spidev_class)) {

unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);

return PTR_ERR(spidev_class);

}

….

}

module_init(spidev_init);

static void __exit spidev_exit(void)

{

……

class_destroy(spidev_class);

……

}

module_exit(spidev_exit);

MODULE_DESCRIPTION(“User mode SPI device interface”);

MODULE_LICENSE(“GPL”);

下面以一个简单字符设备驱动来展示如何使用这几个函数

#include linux/module.h

#include linux/kernel.h

#include linux/init.h

#include linux/fs.h

#include linux/cdev.h

#include linux/device.h

int HELLO_MAJOR = 0;

int HELLO_MINOR = 0;

int NUMBER_OF_DEVICES = 2;

struct class *my_class;

//struct cdev cdev;

//dev_t devno;

struct hello_dev {

struct device *dev;

dev_t chrdev;

struct cdev cdev;

};

static struct hello_dev *my_hello_dev = NULL;

struct file_operations hello_fops = {

.owner = THIS_MODULE

};

static int __init hello_init (void)

{

int err = 0;

struct device *dev;

my_hello_dev = kzalloc(sizeof(struct hello_dev), GFP_KERNEL);

if (NULL == my_hello_dev) {

printk(“%s kzalloc failed!

“,__func__);

return -ENOMEM;

}

devno = MKDEV(HELLO_MAJOR, HELLO_MINOR);

if (HELLO_MAJOR)

err= register_chrdev_region(my_hello_dev-chrdev, 2, “memdev”);

else

{

err = alloc_chrdev_region(my_hello_dev-chrdev, 0, 2, “memdev”);

HELLO_MAJOR = MAJOR(devno);

}

if (err) {

printk(“%s alloc_chrdev_region failed!

“,__func__);

goto alloc_chrdev_err;

}

printk(“MAJOR IS %d

“,HELLO_MAJOR);

cdev_init((my_hello_dev-cdev), hello_fops);

my_hello_dev-cdev.owner = THIS_MODULE;

err = cdev_add((my_hello_dev-cdev), my_hello_dev-chrdev, 1);

if (err) {

printk(“%s cdev_add failed!

“,__func__);

goto cdev_add_err;

}

printk (KERN_INFO “Character driver Registered

“);

my_class =class_create(THIS_MODULE,”hello_char_class”); //类名为hello_char_class

if(IS_ERR(my_class))

{

err = PTR_ERR(my_class);

printk(“%s class_create failed!

“,__func__);

goto class_err;

}

dev = device_create(my_class,NULL,my_hello_dev-chrdev,NULL,”memdev%d”,0); //设备名为memdev

if (IS_ERR(dev)) {

err = PTR_ERR(dev);

gyro_err(“%s device_create failed!

“,__func__);

goto device_err;

}

printk(“hello module initialization

“);

return 0;

device_err:

device_destroy(my_class, my_hello_dev-chrdev);

class_err:

cdev_del(my_hello_dev-chrdev);

cdev_add_err:

unregister_chrdev_region(my_hello_dev-chrdev, 1);

alloc_chrdev_err:

kfree(my_hello_dev);

return err;

}

static void __exit hello_exit (void)

{

cdev_del ((my_hello_dev-cdev));

unregister_chrdev_region (my_hello_dev-chrdev,1);

device_destroy(my_class, devno); //delete device node under /dev//必须先删除设备，再删除class类

class_destroy(my_class); //delete class created by us

printk (KERN_INFO “char driver cleaned up

“);

}

module_init (hello_init);

module_exit (hello_exit);

MODULE_LICENSE (“GPL”);

这样，模块加载后，就能在/dev目录下找到memdev这个设备节点了。

例2:内核中的drivers/i2c/i2c-dev.c

在i2cdev_attach_adapter中调用device_create(i2c_dev_class, adap-dev,

MKDEV(I2C_MAJOR, adap-nr), NULL,

“i2c-%d”, adap-nr);

这样在dev目录就产生i2c-0 或i2c-1节点

下面就是udev应用，udev是应用层的东西，udev需要内核sysfs和tmpfs的支持，sysfs为udev提供设备入口和uevent通道，tmpfs为udev设备文件提供存放空间

udev的源码可以在去相关网站下载，然后就是对其在运行环境下的移植，指定交叉编译环境，修改Makefile下的CROSS_COMPILE，如为mipsel-linux-，DESTDIR=xxx，或直接make CROSS_COMPILE=mipsel-linux-,DESTDIR=xxx 并install

把主要生成的udevd、udevstart拷贝rootfs下的/sbin/目录内，udev的配置文件udev.conf和rules.d下的rules文件拷贝到rootfs下的/etc/目录内

并在rootfs/etc/init.d/rcS中添加以下几行：

echo “Starting udevd…”

/sbin/udevd –daemon

/sbin/udevstart

（原rcS内容如下：

# mount filesystems

/bin/mount -t proc /proc /proc

/bin/mount -t sysfs sysfs /sys

/bin/mount -t tmpfs tmpfs /dev

# create necessary devices

/bin/mknod /dev/null c 1 3

/bin/mkdir /dev/pts

/bin/mount -t devpts devpts /dev/pts

/bin/mknod /dev/audio c 14 4

/bin/mknod /dev/ts c 10 16

）

这样当系统启动后，udevd和udevstart就会解析配置文件，并自动在/dev下创建设备节点文件

以上就是小编对DEVT和devt币为什么会大跌的总结，更多devt币为什么会大跌方面的知识可以关注我们，在网站首页进行搜索你想知道的！

DEVT（devt币为什么会大跌）

欧易okx交易所下载

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