长春电商网站建设公司排名,网站顶部有空白,wordpress cpu检查,网络优化需要哪些知识linux设备驱动模型
为什么需要设备驱动模型
早期内核#xff08;2.4之前#xff09;没有统一的设备驱动模型#xff0c;但照样可以用2.4~2.6期间使用devfs#xff0c;挂载在/dev目录。 需要在内核驱动中创建设备文件(devfs_register)#xff0c;命名死板 2.6以后使用sys…linux设备驱动模型
为什么需要设备驱动模型
早期内核2.4之前没有统一的设备驱动模型但照样可以用2.4~2.6期间使用devfs挂载在/dev目录。 需要在内核驱动中创建设备文件(devfs_register)命名死板 2.6以后使用sysfs挂载在/sys目录 将设备分类、分层次统一进行管理配合udev/mdev守护进程动态创建设备文件命令规则自由制定
sysfs概述
linux系统通过sysfs体现出设备驱动模型
sysfs是一个虚拟文件系统类似proc文件系统目录对应的inode节点会记录基本驱动对象(kobject)从而将系统中的设备组成层次结构用户可以读写目录下的不同文件来配置驱动对象(kobject)的不同属性
设备驱动模型基本元素 kobjectsysfs中的一个目录常用来表示基本驱动对象不允许发送消息到用户空间 ksetsysfs中的一个目录常用来管理kobject允许发送消息到用户空间 kobj_type目录下属性文件的操作接口
驱动模型一 kset可批量管理kobject
kobject无法批量管理kobject
驱动模型二 上层kobject节点无法遍历查找下层kobject
kobject
sysfs中每一个目录都对应一个kobject
include/linux/kobject.h
struct kobject {//用来表示该kobject的名称const char *name;//链表节点struct list_head entry;//该kobject的上层节点构建kobject之间的层次关系struct kobject *parent;//该kobject所属的kset对象用于批量管理kobject对象struct kset *kset;//该Kobject的sysfs文件系统相关的操作和属性struct kobj_type *ktype;//该kobject在sysfs文件系统中对应目录项struct kernfs_node *sd; /* sysfs directory entry *///该kobject的引用次数struct kref kref;
#ifdef CONFIG_DEBUG_KOBJECT_RELEASEstruct delayed_work release;
#endif//记录内核对象的初始化状态unsigned int state_initialized:1;//表示该kobject所代表的内核对象有没有在sysfs建立目录unsigned int state_in_sysfs:1;unsigned int state_add_uevent_sent:1;unsigned int state_remove_uevent_sent:1;unsigned int uevent_suppress:1;
};kset
struct kset {//用来将起中的object对象构建成链表struct list_head list;//自旋锁spinlock_t list_lock;//当前kset内核对象的kobject变量struct kobject kobj;//定义了一组函数指针当kset中的某些kobject对象发生状态变化需要通知用户空间时调用其中的函数来完成const struct kset_uevent_ops *uevent_ops;
}kobj_type
struct kobj_type {//销毁kobject对象时调用void (*release)(struct kobject *kobj);//kobject对象属性文件统一操作接口const struct sysfs_ops *sysfs_ops;//kobject默认属性文件的名字、文件具体操作接口struct attribute **default_attrs; const struct kobj_ns_type_operations *(*child_ns_type)(struct kobject *kobj);const void *(*namespace)(struct kobject *kobj);void (*get_ownership)(struct kobject *kobj, kuid_t *uid, kgid_t *gid);
};kobject驱动的基石
构建一个kobject对象构建一个sysfs中的目录项(kernfs_node)把他们关联起来
重点 关注sysfs目录项与kobject对象的关联过程关注kobject对象默认的属性文件操作接口
kobject_create_and_add()函数
掌握这一个函数即可
lib/kobject.c
struct kobject *kobject_create_and_add(const char *name, struct kobject *parent)
{struct kobject *kobj;int retval;/*创建并初始化一个kobject对象*/kobj kobject_create();if (!kobj)return NULL;/*sysfs创建一个目录项并与kobject对象关联*/retval kobject_add(kobj, parent, %s, name);if (retval) {pr_warn(%s: kobject_add error: %d\n, __func__, retval);kobject_put(kobj);kobj NULL;}return kobj;
}kobject_create()函数
lib/kobject.c
struct kobject *kobject_create(void)
{struct kobject *kobj;/*动态申请内存存放kobject对象*/kobj kzalloc(sizeof(*kobj), GFP_KERNEL);if (!kobj)return NULL;kobject_init(kobj, dynamic_kobj_ktype);return kobj;
}static struct kobj_type dynamic_kobj_ktype {.release dynamic_kobj_release,.sysfs_ops kobj_sysfs_ops,
};const struct sysfs_ops kobj_sysfs_ops {.show kobj_attr_show,.store kobj_attr_store,
};kobject_init()函数
lib/kobject.c
void kobject_init(struct kobject *kobj, struct kobj_type *ktype)
{
...kobject_init_internal(kobj);/*设置目录属性文件的操作接口*/kobj-ktype ktype;return;
...
}kobject_init_internal()函数
lib/kobject.c
static void kobject_init_internal(struct kobject *kobj)
{if (!kobj)return;\/*将kobject的引用计数设置为1*/kref_init(kobj-kref);/*初始化链表节点*/INIT_LIST_HEAD(kobj-entry);/*该kobject对象还没和sysfs目录项关联*/kobj-state_in_sysfs 0;kobj-state_add_uevent_sent 0;kobj-state_remove_uevent_sent 0;/*kobject对象的初始化标志*/kobj-state_initialized 1;
}kobject_add()函数
lib/kobject.c
retval kobject_add(kobj, parent, “%s”, name);
int kobject_add(struct kobject *kobj, struct kobject *parent,const char *fmt, ...)
{va_list args;int retval;
.../*获取第一个可变参数可变参数函数的实现与函数传参的栈结构有关*/va_start(args, fmt);retval kobject_add_varg(kobj, parent, fmt, args);va_end(args);
...return retval;
}kobject_add_varg()函数
lib/kobject.c
static __printf(3, 0) int kobject_add_varg(struct kobject *kobj,struct kobject *parent,const char *fmt, va_list vargs)
{int retval;retval kobject_set_name_vargs(kobj, fmt, vargs);if (retval) {pr_err(kobject: can not set name properly!\n);return retval;}/*第一次设置kobj的parent指针*/kobj-parent parent;return kobject_add_internal(kobj);
}kobject_set_name_vargs()函数
lib/kobject.c
int kobject_set_name_vargs(struct kobject *kobj, const char *fmt,va_list vargs)
{const char *s;.../*参数格式化打印到s字符串中*/s kvasprintf_const(GFP_KERNEL, fmt, vargs);.../*设置kobject对象的名称*/kobj-name s;...
}
kobject_add_internal()函数
lib/kobject.c
static int kobject_add_internal(struct kobject *kobj)
{struct kobject *parent;...parent kobject_get(kobj-parent);if (kobj-kset) {/*如果parent为空parent设置为kobj-kset-kobj*/if (!parent)parent kobject_get(kobj-kset-kobj);/*把该kobject加入到kset链表的末尾*/kobj_kset_join(kobj);/*第二次设置kobj的parent指针*/kobj-parent parent;}...error create_dir(kobj);...kobj-state_in_sysfs 1;...
}create_dir()函数
lib/kobject.c
static int create_dir(struct kobject *kobj)
{const struct kobj_ns_type_operations *ops;int error;error sysfs_create_dir_ns(kobj, kobject_namespace(kobj));...
}sysfs_create_dir_ns()函数
fs/sysfs/dir.c
int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
{struct kernfs_node *parent, *kn;kuid_t uid;kgid_t gid;BUG_ON(!kobj);if (kobj-parent)/*获取上一层节点的目录项*/parent kobj-parent-sd;else/*设置上一层节点的目录项为sysfs根目录*/parent sysfs_root_kn;if (!parent)return -ENOENT;kn kernfs_create_dir_ns(parent, kobject_name(kobj),S_IRWXU | S_IRUGO | S_IXUGO, uid, gid,kobj, ns);.../*kobj对象关联sysfs目录项*/kobj-sd kn;return 0;
}kernfs_create_dir_ns()函数
struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,const char *name, umode_t mode,kuid_t uid, kgid_t gid,void *priv, const void *ns)
{struct kernfs_node *kn;int rc;/* allocate */kn kernfs_new_node(parent, name, mode | S_IFDIR,uid, gid, KERNFS_DIR);.../*sysfs目录项关联kobject对象*/kn-priv priv;...
}kernfs_new_node()函数
struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,const char *name, umode_t mode,kuid_t uid, kgid_t gid,unsigned flags)
{struct kernfs_node *kn;kn __kernfs_new_node(kernfs_root(parent),name, mode, uid, gid, flags);if (kn) {kernfs_get(parent);kn-parent parent;}return kn;
}kobj_type用户空间的法宝 为kobject对象构建多个属性文件为每个属性文件设置具体操作接口vfs的inode对象与sysfs的kernfs_node对象的绑定过程
重点
关注属性文件具体操作接口的赋值过程关注open()、read()、write函数的底层机制
第一阶段属性文件操作接口赋值
sysfs_create_group()函数
fs/sysfs/group.c
创建接口文件并且绑定接口
int sysfs_create_group(struct kobject *kobj,const struct attribute_group *grp)
{return internal_create_group(kobj, 0, grp);
}attribute_group结构体 include/linux/sysfs.h
struct attribute_group {const char *name;umode_t (*is_visible)(struct kobject *,struct attribute *, int);umode_t (*is_bin_visible)(struct kobject *,struct bin_attribute *, int);struct attribute **attrs;struct bin_attribute **bin_attrs;
};struct attribute结构体 include/linux/sysfs.h
struct attribute {const char *name;umode_t mode;
};kobj_attribute结构体
struct kobj_attribute {struct attribute attr;ssize_t (*show)(struct kobject *kobj, struct kobj_attribute *attr,char *buf);ssize_t (*store)(struct kobject *kobj, struct kobj_attribute *attr,const char *buf, size_t count);
};internal_create_group()函数
fs/sysfs/group.c
tatic int internal_create_group(struct kobject *kobj, int update,const struct attribute_group *grp)
{struct kernfs_node *kn;kuid_t uid;kgid_t gid;int error;...if (grp-name)...elsekn kobj-sd;...error create_files(kn, kobj, uid, gid, grp, update);...
} create_files()函数
fs/sysfs/group.c
static int create_files(struct kernfs_node *parent, struct kobject *kobj,kuid_t uid, kgid_t gid,const struct attribute_group *grp, int update)
{struct attribute *const *attr;struct bin_attribute *const *bin_attr;int error 0, i;if (grp-attrs) {for (i 0, attr grp-attrs; *attr !error; i, attr) {umode_t mode (*attr)-mode;...error sysfs_add_file_mode_ns(parent, *attr, false,mode, uid, gid, NULL);...}...
}sysfs_add_file_mode_ns()函数
fs/sysfs/file.c
int sysfs_add_file_mode_ns(struct kernfs_node *parent,const struct attribute *attr, bool is_bin,umode_t mode, kuid_t uid, kgid_t gid, const void *ns)
{struct lock_class_key *key NULL;const struct kernfs_ops *ops;struct kernfs_node *kn;loff_t size;if (!is_bin) {struct kobject *kobj parent-priv;/*kobj_sysfs_ops*/const struct sysfs_ops *sysfs_ops kobj-ktype-sysfs_ops;...if (sysfs_ops-show sysfs_ops-store) {if (mode SYSFS_PREALLOC)ops sysfs_prealloc_kfops_rw;elseops sysfs_file_kfops_rw;else if...}...kn __kernfs_create_file(parent, attr-name, mode 0777, uid, gid,size, ops, (void *)attr, ns, key);...
}kernfs_ops节点的操作函数
static const struct kernfs_ops sysfs_file_kfops_rw {.seq_show sysfs_kf_seq_show,.write sysfs_kf_write,
};__kernfs_create_file()函数
struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,const char *name,umode_t mode, kuid_t uid, kgid_t gid,loff_t size,const struct kernfs_ops *ops,void *priv, const void *ns,struct lock_class_key *key)
{struct kernfs_node *kn;unsigned flags;int rc;flags KERNFS_FILE;kn kernfs_new_node(parent, name, (mode S_IALLUGO) | S_IFREG,uid, gid, flags);if (!kn)return ERR_PTR(-ENOMEM);/*操作接口赋值*/kn-attr.ops ops;kn-attr.size size;kn-ns ns;/*文件属性赋值*/kn-priv priv;if (ops-seq_show)kn-flags | KERNFS_HAS_SEQ_SHOW;...
}第二阶段open()\read()\write()的底层机制
kernfs_init_inode()函数
static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
{kernfs_get(kn);/*sysfs的kernels_node赋值给vfs的inode*/inode-i_private kn;inode-i_mapping-a_ops kernfs_aops;inode-i_op kernfs_iops;inode-i_generation kn-id.generation;set_default_inode_attr(inode, kn-mode);kernfs_refresh_inode(kn, inode);/* 判断sysfs的kernels_node类型 */switch (kernfs_type(kn)) {case KERNFS_DIR:inode-i_op kernfs_dir_iops;inode-i_fop kernfs_dir_fops;if (kn-flags KERNFS_EMPTY_DIR)make_empty_dir_inode(inode);break;case KERNFS_FILE:inode-i_size kn-attr.size;/*文件的操作接口*/inode-i_fop kernfs_file_fops;break;case KERNFS_LINK:inode-i_op kernfs_symlink_iops;break;default:BUG();}unlock_new_inode(inode);
}const struct file_operations kernfs_file_fops {.read kernfs_fop_read,.write kernfs_fop_write,.llseek generic_file_llseek,.mmap kernfs_fop_mmap,.open kernfs_fop_open,.release kernfs_fop_release,.poll kernfs_fop_poll,.fsync noop_fsync,
};kernfs_fop_open()函数
static int kernfs_fop_open(struct inode *inode, struct file *file)
{struct kernfs_node *kn inode-i_private;struct kernfs_open_file *of;...of kzalloc(sizeof(struct kernfs_open_file), GFP_KERNEL);.../*sysfs中文件的kernfs_node赋值给of-kn*/of-kn kn;/*进程的struct file赋值给of-file/of-file file;...if (ops-seq_show)error seq_open(file, kernfs_seq_ops);.../*struct file的私有指针赋值给of-seq_file */of-seq_file file-private_data;/*of赋值给of-seq_file-private*/of-seq_file-private of;...}static const struct seq_operations kernfs_seq_ops {.start kernfs_seq_start,.next kernfs_seq_next,.stop kernfs_seq_stop,.show kernfs_seq_show,
};seq_open
int seq_open(struct file *file, const struct seq_operations *op)
{struct seq_file *p;WARN_ON(file-private_data);p kmem_cache_zalloc(seq_file_cache, GFP_KERNEL);if (!p)return -ENOMEM;file-private_data p;...p-op op;...
}kernfs_fop_read()函数
static ssize_t kernfs_fop_read(struct file *file, char __user *user_buf,size_t count, loff_t *ppos)
{struct kernfs_open_file *of kernfs_of(file);if (of-kn-flags KERNFS_HAS_SEQ_SHOW)return seq_read(file, user_buf, count, ppos);elsereturn kernfs_file_direct_read(of, user_buf, count, ppos);
}
kernfs_of()函数
static struct kernfs_open_file *kernfs_of(struct file *file)
{return ((struct seq_file *)file-private_data)-private;
}seq_read()函数
ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
{struct seq_file *m file-private_data;...err m-op-show(m, p);...err copy_to_user(buf, m-buf, n);...
}kernfs_seq_show()函数
static int kernfs_seq_show(struct seq_file *sf, void *v)
{struct kernfs_open_file *of sf-private;...return of-kn-attr.ops-seq_show(sf, v);
}sysfs_kf_seq_show()函数
static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
{struct kernfs_open_file *of sf-private;struct kobject *kobj of-kn-parent-priv;const struct sysfs_ops *ops sysfs_file_ops(of-kn);ssize_t count;char *buf;count seq_get_buf(sf, buf);if (count PAGE_SIZE) {seq_commit(sf, -1);return 0;}memset(buf, 0, PAGE_SIZE);/** Invoke show(). Control may reach here via seq file lseek even* if ops-show() isnt implemented.*/if (ops-show) {count ops-show(kobj, of-kn-priv, buf);if (count 0)return count;}/** The code works fine with PAGE_SIZE return but its likely to* indicate truncated result or overflow in normal use cases.*/if (count (ssize_t)PAGE_SIZE) {printk(fill_read_buffer: %pS returned bad count\n,ops-show);/* Try to struggle along */count PAGE_SIZE - 1;}seq_commit(sf, count);return 0;
}sysfs_file_ops()函数
static const struct sysfs_ops *sysfs_file_ops(struct kernfs_node *kn)
{struct kobject *kobj kn-parent-priv;if (kn-flags KERNFS_LOCKDEP)lockdep_assert_held(kn);return kobj-ktype ? kobj-ktype-sysfs_ops : NULL;
}seq_get_buf()函数
static inline size_t seq_get_buf(struct seq_file *m, char **bufp)
{BUG_ON(m-count m-size);if (m-count m-size)*bufp m-buf m-count;else*bufp NULL;return m-size - m-count;
}kobj_attr_show()函数
static ssize_t kobj_attr_show(struct kobject *kobj, struct attribute *attr,char *buf)
{struct kobj_attribute *kattr;ssize_t ret -EIO;/*根据结构体成员的内存地址获取结构体的地址*/kattr container_of(attr, struct kobj_attribute, attr);if (kattr-show)ret kattr-show(kobj, kattr, buf);return ret;
}设备驱动模型实验1-kobject点灯
实验思路
内核模块led驱动kobjectkobj_attribute
内核模块
动态加载功能
led驱动
控制硬件led
kobject
在/sys创建目录项
kobj_attribute
为kobject对象的属性文件提供独有的读写接口
kset驱动的骨架
kobject的容器体现设备驱动的层次关系 kset_create_and_add()函数
lib/kobject.c
struct kset *kset_create_and_add(const char *name,
const struct kset_uevent_ops *uevent_ops,struct kobject *parent_kobj)
{struct kset *kset;int error;kset kset_create(name, uevent_ops, parent_kobj);if (!kset)return NULL;error kset_register(kset);if (error) {kfree(kset);return NULL;}return kset;
}kset_create()函数
lib/kobject.c
static struct kset *kset_create(const char *name,const struct kset_uevent_ops *uevent_ops,struct kobject *parent_kobj)
{struct kset *kset;int retval;kset kzalloc(sizeof(*kset), GFP_KERNEL);if (!kset)return NULL;retval kobject_set_name(kset-kobj, %s, name);if (retval) {kfree(kset);return NULL;}/*注册消息发送接口*/kset-uevent_ops uevent_ops;kset-kobj.parent parent_kobj;kset-kobj.ktype kset_ktype;kset-kobj.kset NULL;return kset;
}kset_init()函数
lib/kobject.c
void kset_init(struct kset *k)
{kobject_init_internal(k-kobj);INIT_LIST_HEAD(k-list);spin_lock_init(k-list_lock);
}kset_register()函数
lib/kobject.c
int kset_register(struct kset *k)
{int err;if (!k)return -EINVAL;kset_init(k);err kobject_add_internal(k-kobj);if (err)return err;/*发送驱动模型消息到应用层*/kobject_uevent(k-kobj, KOBJ_ADD);return 0;
}
