“asm/semaphore.h: No such file or directory”
今天编译发现一个error: “asm/semaphore.h: No such file or directory” ,发现2.6.19和2.6.31对这个信号量声明并不相同
[patch] include linux/semaphore.h for kernel 2.6.26 and onwards
Description
The kernel/xpp/xpd.h includes
As of Linux kernel version 2.6.26, the asm/semaphore.h has been deprecated, favoring an include of
When attempting to compile zaptel in Linux 2.6.27, as the current sources are, we get an error 'unable to include
This patch performs the check for Linux kernel version 2.6.26, if the version is before this, the existing #include
but if Linux kernel version >= 2.6.26 is found, then #include
https://issues.asterisk.org/jira/browse/ZAP-353
一些参考文章:
声明一个信号量，使用DECLARE_MUTEX(ADC_LOCK)或DEFINE_SEMAPHORE(ADC_LOCK)，这很好懂，但是这个宏到底做了些什么呢？这就要深入到这个宏定义所在文件中研究了(在
对于这两宏，想说几句，因为最近一次移植新版本的内核(2.6.37.3)，就是因为DECLARE_MUTEX不再使用而导致我浪费了几天的时间。据本人考查，最早说要将DECLARE_MUTEX改为DEFINE_SEMAPHORE是在08年10月底，参见地址http://lwn.net/Articles/304725/。而在Linux Cross Reference(网站如http://lxr.free-electrons.com/等等)中发现，直到2.6.36才出现DEFINE_SEMAPHORE，而且这个版本中两个宏同时存在。但是到了2.6.37，DECLARE_MUTEX这个宏却不存在了。
不由得想到某个论坛的签名，原文是英文的，原文及出自一时不知道去哪找了。大意是说UNIX最好的地方是什么？答曰有社区，再问UNIX不好的地方是什么？答曰有太多的社区。像Linux内核这东西，版本更新太快了，各种结构体名称变化、成员变化及新增函数、删除函数，让人目不暇接。虽说一味追求新版本不好，但是心理作用，还是选择新的版本来移植。新的东西当然有它的好，像买台android的手机，就得不停的刷机，不断折腾，这跟搞Linux在某种程度上是一样的。
http://www.latelee.org/embedded-linux/127-mutil-channel-adc-of-s3c2410-write.html
http://71151461.cn/
Linux 2.6.36以后file_operations和DECLARE_MUTEX 和kmem_cache_create的变化
今天尝试在2.6.39内核上编译一个驱动, 在编译驱动时发现从2.6.36的内核开始，include/linux/semaphore.h 和 include/linux/fs.h中有了两处变化与驱动相关：
1， 在include/linux/semaphore.h 中
在编译阶段初始化的变化：
将#define DECLARE_MUTEX(name) 改成了 #define DEFINE_SEMAPHORE(name)
#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,36)
DECLARE_MUTEX(led_sem);
#else
DEFINE_SEMAPHORE(led_sem);
#endif
在运行时初始化得变化（动态分配）：
以去除：
void init_MUTEX(struct semaphore *sem);
void init_MUTEX_LOCKED(struct semaphore *sem);
可通过以下初始：
void sema_init(struct semaphore *sem, int val);
2，后备缓存：include/linux/slab.h
kmem_cache_t 类型已改为：
struct kmem_cache
创建缓存对象函数
kmem_cache_t *kmem_cache_create(const char *name, size_t size,
size_t offset,
unsigned long flags,
void (*constructor)(void *, kmem_cache_t *,
unsigned long flags), void (*destructor)(void *, kmem_cache_t *, unsigned long flags));
已改为(参数少了一个，返回值内型变化)：
struct kmem_cache *kmem_cache_create(const char *name, size_t size,
size_t offset,
unsigned long flags,
void (*)(void ));
2， file_operations结构体有了一些变化，它去掉了：
int (*ioctl) (struct inode *, struct file *, unsigned int, unsigned long);
另外添加了：
long (*fallocate)(struct file *file, int mode, loff_t offset,loff_t len);
这是2.6.36的内核里的定义include/linux/fs.h：
struct file_operations {
struct module *owner;
loff_t (*llseek) (struct file *, loff_t, int);
ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
ssize_t (*aio_read) (struct kiocb *, const struct iovec *, unsigned long, loff_t);
ssize_t (*aio_write) (struct kiocb *, const struct iovec *, unsigned long, loff_t);
int (*readdir) (struct file *, void *, filldir_t);
unsigned int (*poll) (struct file *, struct poll_table_struct *);
//从2.6.36开始删除ioctl(), 2.6.35中有
long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
int (*mmap) (struct file *, struct vm_area_struct *);
int (*open) (struct inode *, struct file *);
int (*flush) (struct file *, fl_owner_t id);
int (*release) (struct inode *, struct file *);
int (*fsync) (struct file *, int datasync);
int (*aio_fsync) (struct kiocb *, int datasync);
int (*fasync) (int, struct file *, int);
int (*lock) (struct file *, int, struct file_lock *);
ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);
unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
int (*check_flags)(int);
int (*flock) (struct file *, int, struct file_lock *);
ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
int (*setlease)(struct file *, long, struct file_lock **);
// long (*fallocate)(struct file *file, int mode, loff_t offset, loff_t len); 从2.6.38内核开始添加该项，2.6.37以下无
};
下面是Linux-2.6.35里的file_operations
struct file_operations {
struct module *owner;
loff_t (*llseek) (struct file *, loff_t, int);
ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
ssize_t (*aio_read) (struct kiocb *, const struct iovec *, unsigned long, loff_t);
ssize_t (*aio_write) (struct kiocb *, const struct iovec *, unsigned long, loff_t);
int (*readdir) (struct file *, void *, filldir_t);
unsigned int (*poll) (struct file *, struct poll_table_struct *);
int (*ioctl) (struct inode *, struct file *, unsigned int, unsigned long);
long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
int (*mmap) (struct file *, struct vm_area_struct *);
int (*open) (struct inode *, struct file *);
int (*flush) (struct file *, fl_owner_t id);
int (*release) (struct inode *, struct file *);
int (*fsync) (struct file *, struct dentry *, int datasync);
int (*aio_fsync) (struct kiocb *, int datasync);
int (*fasync) (int, struct file *, int);
int (*lock) (struct file *, int, struct file_lock *);
ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);
unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
int (*check_flags)(int);
int (*flock) (struct file *, int, struct file_lock *);
ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
int (*setlease)(struct file *, long, struct file_lock **);
};
[guowenxue@localhost at91sam9260]$ make
make[1]: Entering directory `/usr/.devices_group/guowenxue/l350-dev06/src/kernel/linux-2.6.38'
CC [M] /usr/.devices_group/guowenxue/embedded_project/drivers/at91sam9260/dev_skeleton.o
/usr/.devices_group/guowenxue/embedded_project/drivers/at91sam9260/dev_skeleton.c:93: error: unknown field 'ioctl' specified in initializer
/usr/.devices_group/guowenxue/embedded_project/drivers/at91sam9260/dev_skeleton.c:93: warning: initialization from incompatible pointer type
make[2]: *** [/usr/.devices_group/guowenxue/embedded_project/drivers/at91sam9260/dev_skeleton.o] Error 1
make[1]: *** [_module_/usr/.devices_group/guowenxue/embedded_project/drivers/at91sam9260] Error 2
make[1]: Leaving directory `/usr/.devices_group/guowenxue/l350-dev06/src/kernel/linux-2.6.38'
make: *** [modules] Error 2
参考别的字符设备的驱动drivers/char/ppdev.c：
static const struct file_operations pp_fops = {
.owner = THIS_MODULE,
.llseek = no_llseek,
.read = pp_read,
.write = pp_write,
.poll = pp_poll,
.unlocked_ioctl = pp_ioctl,
.open = pp_open,
.release = pp_release,
};
这里ioctl()已使用unlocked_ioctl代替。
但这里不是一个简单的替换，要注意unlocked_ioctl和ioctl的函数原型并不一致。
unlocked_ioctl: long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
ioctl: int(*ioctl) (struct inode *,struct file *, unsigned int, unsigned long);
The 'inode' value that was passed to 'ioctl' function is available for use with the 'unlocked_ioctl' function by way of filp->d_entry->d_inode:
long (*unlocked_ioctl) (struct file *filp, unsigned int cmd, unsigned long arg);
...
struct inode *inode = filp->f_path.dentry->d_inode
There is a nice explanation of this at http://lwn.net/Articles/119652/
如：
static long dev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
int index = NUM(file->f_path.dentry->d_inode->i_rdev); /*Which LED*/
.....
}
--------------------------------------
在file_operations 结构体中，会看到许多函数指针所指向的函数都必须传进struct file 结构体指针struct file * 作为参数。struct file 结构体定义在
引用
struct file {
union {
struct list_head fu_list;
struct rcu_head fu_rcuhead;
} f_u;
struct path f_path;
#definef_dentry f_path.dentry
#definef_vfsmnt f_path.mnt
const struct file_operations *f_op;
spinlock_t f_lock;
atomic_long_t f_count;
unsigned int f_flags;
fmode_t f_mode;
loff_t f_pos;
struct fown_struct f_owner;
const struct cred *f_cred;
struct file_ra_state f_ra;
u64 f_version;
#ifdef CONFIG_SECURITY
void *f_security;
#endif
void *private_data;
#ifdef CONFIG_EPOLL
struct list_head f_ep_links;
#endif
struct address_space *f_mapping;
#ifdef CONFIG_DEBUG_WRITECOUNT
unsigned long f_mnt_write_state;
#endif
};
在设备驱动中，struct file 结构体也是一个非常重要的数据结构。注意的是，这里的file 和应用程序中的FILE 流指针没有什么关系，FILE 定义在C 库中，它永远不会出现在内核代码中。
file structure 结构代表一个打开的文件(open file).(打开的文件并没有确切的指定到哪个设备驱动，实际上每个打开的文件都与内核空间中的struct file 结构相关联)。
file structure 结构在调用open 打开一个文件时由内核创建，并会被传递给任一个对这个打开文件进行操作的函数；当所有事情都做完后，会调用close() 关闭掉文件，此时内核释放这个数据结构。
一般地，在内核源码中，struct file 结构体的指针往往写成filp 。
struct file 中的几个重要成员：
mode_t f_mode;
文件模式根据FMMODE_READ 和FMODE_WRITE 位来识别文件是否可读或可写，或是可读可写。在read() 和write() 系统调用中，没有必要对此权限进行检查，因为内核已经在你的系统调用之前已经做了检查。如果文件没有相应的读或写权限，那么如果尝试读写都将被拒绝，驱动程序甚至对此情况毫无知觉。
loff_t f_pos;
此变量表示当前的文件读写位置。loff_t 在所有的平台上都是64 位的变量( long long 型, gcc 专用术语)。驱动程序如果想知道当前在文件中所处位置，那么可以通过读取此变量得知，但是一般地不应直接对此进行更改。通过llseek() 方法可以改变文件位置。
unsigned int f_flags;
这是表示如O_RDONLY, O_NONBLOCK与O_SYNC 这样的标志。一个驱动程序应该检查O_NONBLOCK 标志，以查看是否有非阻塞操作的请求。其它的标志用得比较少。需要注意的是，检查read/write 权限应该是通过检查f_mode 得到而不是f_flags 。所有的标志定义在头文件linux/fcntl.h 中可以看到。
struct file_operations*f_op;
内核安排这个指针作为它的open 实现的一部分，当需要分派什么操作时，会读取它。filp->f_op 因为不会被内核保存起来以在其后之用，所以我们可以改变我们对相关文件的操作，在对文件使用新的操作方法时，我们就会转移到相应调用上。
void *private_data;
在对驱动调用open 方法之前，open() 系统调用会这个指针设置为NULL 。用户可以自由使用这个域，或者对其忽略。可以使用这个域之想分配的数据空间，但必须记得在内核销毁file structure 之前在release 方法里释放掉原来分配的内存。private_data 对于系统调用之间信息的保存会显得非常有用。
struct dentry*f_dentry;
目录入口(dentry) 结构与文件相关。一般的，除了在以filp->f_dentry->d_inode 来访问inode 结构时，我们不太关心dentry 这个结构。
http://blog.csdn.net/yhguo2008/article/details/6424855