Uevent 上报event事件给上层的详细讲解
2013-12-06 16:41
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http://blog.csdn.net/sunweizhong1024/article/details/7928530
headphone_event 上报事件的分析
本文章讲解插入headphone的时候，向上层上报event函数的整个过程
headphone_event(wm8903->hp_state);
当有headphone 插入的时候，那么就将hp_state的状态设置为1
#ifdef CONFIG_I_LOVE_PBJ30
void headphone_event(int state)
{
switch_set_state(&wired_switch_dev, state);
}
EXPORT_SYMBOL_GPL(headphone_event);
#endif
headphone_event 函数会调用switch_set_state函数进行上报事件
staticstruct switch_dev wired_switch_dev = {
.name = "h2w",
};
void switch_set_state(struct switch_dev *sdev, int state)
{
char name_buf[120];
char state_buf[120];
char *prop_buf;
char *envp[3];
int env_offset = 0;
int length;
if (sdev->state != state) {
sdev->state = state;
prop_buf = (char *)get_zeroed_page(GFP_KERNEL);
if (prop_buf) {
length = name_show(sdev->dev, NULL, prop_buf);
if (length > 0) {
if (prop_buf[length - 1] == '\n')
prop_buf[length - 1] = 0;
snprintf(name_buf, sizeof(name_buf),
"SWITCH_NAME=%s", prop_buf);
envp[env_offset++] = name_buf;
}
length = state_show(sdev->dev, NULL, prop_buf);
if (length > 0) {
if (prop_buf[length - 1] == '\n')
prop_buf[length - 1] = 0;
snprintf(state_buf, sizeof(state_buf),
"SWITCH_STATE=%s", prop_buf);
envp[env_offset++] = state_buf;
}
envp[env_offset] = NULL;
kobject_uevent_env(&sdev->dev->kobj, KOBJ_CHANGE,
envp);
free_page((unsignedlong)prop_buf);
} else {
printk(KERN_ERR "out of memory in switch_set_state\n");
kobject_uevent(&sdev->dev->kobj, KOBJ_CHANGE);
}
}
}
EXPORT_SYMBOL_GPL(switch_set_state);
讲解下上的switch_set_state函数
我们首先会判断sdev里面的状态和我们需要设置的状态是否一样，如果一样的话，那么就不需要去管它，如果不一样的话，那么就将state的值修改
上面主要会调用以下几个函数：
name_show:
state_show:
kobject_uevent_env:
在switch_set_state函数里面，会申请一个buffer，然后调用name_show函数
static ssize_t name_show(struct device *dev, struct device_attribute
*attr,
char *buf)
{
struct switch_dev *sdev = (struct switch_dev
*)
dev_get_drvdata(dev);
if (sdev->print_name) {
int ret = sdev->print_name(sdev, buf);
if (ret >= 0)
return ret;
}
return sprintf(buf, "%s\n", sdev->name);
}
name_show函数会判断sdev里面的print_name函数有没有被实现，如果没有实现的话，那么就将sdev->name的值输入到buf中去
我们的sdev里面实现的如下：
staticstruct switch_dev wired_switch_dev = {
.name = "h2w",
};
所以就直接将name 输入到buf中去
然后将输入到buf里面的值赋值到envp数组里面去：envp[env_offset++] = name_buf;
接下来的state_show函数的执行和上面的name_show函数是一样的，只是一个输出的是name，另外一个是state
也是将state的值赋值到envp 的数组里面去
接下来会调用kobject_uevent_env函数进行上报事件
kobject_uevent_env(&sdev->dev->kobj, KOBJ_CHANGE,
envp);
kobject_uevent_env函数会首先判断 我这个kobject是属于哪个kset里面的，然后找出这个kset里面的uevent_ops
kobject_uevent_env函数的实现全部过程如下：
int kobject_uevent_env(struct kobject *kobj, enum kobject_action
action,
char *envp_ext[])
{
struct kobj_uevent_env *env;
constchar *action_string = kobject_actions[action];
constchar *devpath = NULL;
constchar *subsystem;
struct kobject *top_kobj;
struct kset *kset;
conststruct kset_uevent_ops *uevent_ops;
u64 seq;
int i = 0;
int retval = 0;
#ifdef CONFIG_NET
struct uevent_sock *ue_sk;
#endif
pr_debug("kobject: '%s' (%p): %s\n",
kobject_name(kobj), kobj, __func__);
/* search the kset we belong to */
top_kobj = kobj;
while (!top_kobj->kset && top_kobj->parent)//取出这个kobject属于哪一个kset
top_kobj = top_kobj->parent;
if (!top_kobj->kset) {
pr_debug("kobject: '%s' (%p): %s: attempted to send uevent "
"without kset!\n", kobject_name(kobj), kobj,
__func__);
return -EINVAL;
}
kset = top_kobj->kset;//找到这个kobject的kset成员
uevent_ops = kset->uevent_ops; //找到这个kset创建的时候，kset里面的uevent_ops成员
/* skip the event, if uevent_suppress is set*/
if (kobj->uevent_suppress) {//判断kobject里面有没有uvent_supress，如果有那么就代表这个
event是忽略的
pr_debug("kobject: '%s' (%p): %s: uevent_suppress "
"caused the event to drop!\n",
kobject_name(kobj), kobj, __func__);
return 0;
}
/* skip the event, if the filter returns zero. */
if (uevent_ops && uevent_ops->filter)
if (!uevent_ops->filter(kset, kobj)) {//kset里面的uevent_ops里面的filter成员决定是否将事件传递到用户空间去，如果返回0的话，那么就直接忽略，通过代码看的出来
pr_debug("kobject: '%s' (%p): %s: filter function "
"caused the event to drop!\n",
kobject_name(kobj), kobj, __func__);
return 0;
}
/* originating subsystem */
if (uevent_ops && uevent_ops->name)
subsystem = uevent_ops->name(kset, kobj);//调用uevent_ops里面的name成员将字符串传递给用户空间的热插拔程序
else
subsystem = kobject_name(&kset->kobj);
if (!subsystem) {
pr_debug("kobject: '%s' (%p): %s: unset subsystem caused the "
"event to drop!\n", kobject_name(kobj), kobj,
__func__);
return 0;
}
/* environment buffer */
env = kzalloc(sizeof(struct kobj_uevent_env),
GFP_KERNEL);
if (!env)
return -ENOMEM;
/* complete object path */
devpath = kobject_get_path(kobj, GFP_KERNEL);
if (!devpath) {
retval = -ENOENT;
goto exit;
}
/* default keys */
retval = add_uevent_var(env, "ACTION=%s", action_string);
if (retval)
goto exit;
retval = add_uevent_var(env, "DEVPATH=%s", devpath);
if (retval)
goto exit;
retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem);
if (retval)
goto exit;
/* keys passed in from the caller */
if (envp_ext) {
for (i = 0; envp_ext[i]; i++) {
retval = add_uevent_var(env, "%s", envp_ext[i]);//将我们设置的参数，添加到环境变量中去
if (retval)
goto exit;
}
}
/* let the kset specific function add its stuff */
if (uevent_ops && uevent_ops->uevent) {
retval = uevent_ops->uevent(kset, kobj, env);
if (retval) {
pr_debug("kobject: '%s' (%p): %s: uevent() returned "
"%d\n", kobject_name(kobj), kobj,
__func__, retval);
goto exit;
}
}
/*
* Mark "add" and "remove" events in the object to ensure proper
* events to userspace during automatic cleanup. If the object did
* send an "add" event, "remove" will automatically generated by
* the core, if not already done by the caller.
*/
if (action == KOBJ_ADD)
kobj->state_add_uevent_sent = 1;
elseif (action == KOBJ_REMOVE)
kobj->state_remove_uevent_sent = 1;
/* we will send an event, so request a new sequence number */
spin_lock(&sequence_lock);
seq = ++uevent_seqnum;
spin_unlock(&sequence_lock);
retval = add_uevent_var(env, "SEQNUM=%llu", (unsignedlonglong)seq);
if (retval)
goto exit;
#if defined(CONFIG_NET)
/* send netlink message */
mutex_lock(&uevent_sock_mutex);
list_for_each_entry(ue_sk, &uevent_sock_list, list) {
struct sock *uevent_sock = ue_sk->sk;
struct sk_buff *skb;
size_t len;
/* allocate message with the maximum possible size */
len = strlen(action_string) + strlen(devpath) + 2;
skb = alloc_skb(len + env->buflen, GFP_KERNEL);
if (skb) {
char *scratch;
/* add header */
scratch = skb_put(skb, len);
sprintf(scratch, "%s@%s", action_string, devpath);
/* copy keys to our continuous event payload buffer */
for (i = 0; i < env->envp_idx; i++) {
len = strlen(env->envp[i]) + 1;
scratch = skb_put(skb, len);
strcpy(scratch, env->envp[i]);
}
NETLINK_CB(skb).dst_group = 1;
retval = netlink_broadcast_filtered(uevent_sock, skb,
0, 1, GFP_KERNEL,
kobj_bcast_filter,
kobj);
/* ENOBUFS should be handled in userspace */
if (retval == -ENOBUFS)
retval = 0;
} else
retval = -ENOMEM;
}
mutex_unlock(&uevent_sock_mutex);
#endif
/* call uevent_helper, usually only enabled during early boot */
if (uevent_helper[0] && !kobj_usermode_filter(kobj)) {
char *argv [3];
argv [0] = uevent_helper;
argv [1] = (char *)subsystem;
argv [2] = NULL;
retval = add_uevent_var(env, "HOME=/");
if (retval)
goto exit;
retval = add_uevent_var(env,
"PATH=/sbin:/bin:/usr/sbin:/usr/bin");
if (retval)
goto exit;
retval = call_usermodehelper(argv[0], argv,
env->envp, UMH_WAIT_EXEC);
}
exit:
kfree(devpath);
kfree(env);
return retval;
}
EXPORT_SYMBOL_GPL(kobject_uevent_env);
看下如何将用户空间需要的参数添加到环境变量中去的？？
传进去需要的参数
add_uevent_var(env, "%s", envp_ext[i]);
**
* add_uevent_var - add key value string to the environment buffer
* @env: environment buffer structure
* @format: printf format for the key=value pair
*
* Returns 0 if environment variable was added successfully or -ENOMEM
* if no space was available.
*/
int add_uevent_var(struct kobj_uevent_env *env, constchar *format,
...)
{
va_list args;
int len;
if (env->envp_idx >= ARRAY_SIZE(env->envp))
{
WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
return -ENOMEM;
}
va_start(args, format);
len = vsnprintf(&env->buf[env->buflen],
sizeof(env->buf) - env->buflen,
format, args);
va_end(args);
if (len >= (sizeof(env->buf)
- env->buflen)) {
WARN(1, KERN_ERR "add_uevent_var: buffer size too small\n");
return -ENOMEM;
}
env->envp[env->envp_idx++] = &env->buf[env->buflen];
env->buflen += len + 1;
return 0;
}
EXPORT_SYMBOL_GPL(add_uevent_var);
上面的函数在将参数添加到环境变量中去，如果添加添加成功的话，那么就返回0
headphone_event 上报事件的分析
本文章讲解插入headphone的时候，向上层上报event函数的整个过程
headphone_event(wm8903->hp_state);
当有headphone 插入的时候，那么就将hp_state的状态设置为1
#ifdef CONFIG_I_LOVE_PBJ30
void headphone_event(int state)
{
switch_set_state(&wired_switch_dev, state);
}
EXPORT_SYMBOL_GPL(headphone_event);
#endif
headphone_event 函数会调用switch_set_state函数进行上报事件
staticstruct switch_dev wired_switch_dev = {
.name = "h2w",
};
void switch_set_state(struct switch_dev *sdev, int state)
{
char name_buf[120];
char state_buf[120];
char *prop_buf;
char *envp[3];
int env_offset = 0;
int length;
if (sdev->state != state) {
sdev->state = state;
prop_buf = (char *)get_zeroed_page(GFP_KERNEL);
if (prop_buf) {
length = name_show(sdev->dev, NULL, prop_buf);
if (length > 0) {
if (prop_buf[length - 1] == '\n')
prop_buf[length - 1] = 0;
snprintf(name_buf, sizeof(name_buf),
"SWITCH_NAME=%s", prop_buf);
envp[env_offset++] = name_buf;
}
length = state_show(sdev->dev, NULL, prop_buf);
if (length > 0) {
if (prop_buf[length - 1] == '\n')
prop_buf[length - 1] = 0;
snprintf(state_buf, sizeof(state_buf),
"SWITCH_STATE=%s", prop_buf);
envp[env_offset++] = state_buf;
}
envp[env_offset] = NULL;
kobject_uevent_env(&sdev->dev->kobj, KOBJ_CHANGE,
envp);
free_page((unsignedlong)prop_buf);
} else {
printk(KERN_ERR "out of memory in switch_set_state\n");
kobject_uevent(&sdev->dev->kobj, KOBJ_CHANGE);
}
}
}
EXPORT_SYMBOL_GPL(switch_set_state);
讲解下上的switch_set_state函数
我们首先会判断sdev里面的状态和我们需要设置的状态是否一样，如果一样的话，那么就不需要去管它，如果不一样的话，那么就将state的值修改
上面主要会调用以下几个函数：
name_show:
state_show:
kobject_uevent_env:
在switch_set_state函数里面，会申请一个buffer，然后调用name_show函数
static ssize_t name_show(struct device *dev, struct device_attribute
*attr,
char *buf)
{
struct switch_dev *sdev = (struct switch_dev
*)
dev_get_drvdata(dev);
if (sdev->print_name) {
int ret = sdev->print_name(sdev, buf);
if (ret >= 0)
return ret;
}
return sprintf(buf, "%s\n", sdev->name);
}
name_show函数会判断sdev里面的print_name函数有没有被实现，如果没有实现的话，那么就将sdev->name的值输入到buf中去
我们的sdev里面实现的如下：
staticstruct switch_dev wired_switch_dev = {
.name = "h2w",
};
所以就直接将name 输入到buf中去
然后将输入到buf里面的值赋值到envp数组里面去：envp[env_offset++] = name_buf;
接下来的state_show函数的执行和上面的name_show函数是一样的，只是一个输出的是name，另外一个是state
也是将state的值赋值到envp 的数组里面去
接下来会调用kobject_uevent_env函数进行上报事件
kobject_uevent_env(&sdev->dev->kobj, KOBJ_CHANGE,
envp);
kobject_uevent_env函数会首先判断 我这个kobject是属于哪个kset里面的，然后找出这个kset里面的uevent_ops
kobject_uevent_env函数的实现全部过程如下：
int kobject_uevent_env(struct kobject *kobj, enum kobject_action
action,
char *envp_ext[])
{
struct kobj_uevent_env *env;
constchar *action_string = kobject_actions[action];
constchar *devpath = NULL;
constchar *subsystem;
struct kobject *top_kobj;
struct kset *kset;
conststruct kset_uevent_ops *uevent_ops;
u64 seq;
int i = 0;
int retval = 0;
#ifdef CONFIG_NET
struct uevent_sock *ue_sk;
#endif
pr_debug("kobject: '%s' (%p): %s\n",
kobject_name(kobj), kobj, __func__);
/* search the kset we belong to */
top_kobj = kobj;
while (!top_kobj->kset && top_kobj->parent)//取出这个kobject属于哪一个kset
top_kobj = top_kobj->parent;
if (!top_kobj->kset) {
pr_debug("kobject: '%s' (%p): %s: attempted to send uevent "
"without kset!\n", kobject_name(kobj), kobj,
__func__);
return -EINVAL;
}
kset = top_kobj->kset;//找到这个kobject的kset成员
uevent_ops = kset->uevent_ops; //找到这个kset创建的时候，kset里面的uevent_ops成员
/* skip the event, if uevent_suppress is set*/
if (kobj->uevent_suppress) {//判断kobject里面有没有uvent_supress，如果有那么就代表这个
event是忽略的
pr_debug("kobject: '%s' (%p): %s: uevent_suppress "
"caused the event to drop!\n",
kobject_name(kobj), kobj, __func__);
return 0;
}
/* skip the event, if the filter returns zero. */
if (uevent_ops && uevent_ops->filter)
if (!uevent_ops->filter(kset, kobj)) {//kset里面的uevent_ops里面的filter成员决定是否将事件传递到用户空间去，如果返回0的话，那么就直接忽略，通过代码看的出来
pr_debug("kobject: '%s' (%p): %s: filter function "
"caused the event to drop!\n",
kobject_name(kobj), kobj, __func__);
return 0;
}
/* originating subsystem */
if (uevent_ops && uevent_ops->name)
subsystem = uevent_ops->name(kset, kobj);//调用uevent_ops里面的name成员将字符串传递给用户空间的热插拔程序
else
subsystem = kobject_name(&kset->kobj);
if (!subsystem) {
pr_debug("kobject: '%s' (%p): %s: unset subsystem caused the "
"event to drop!\n", kobject_name(kobj), kobj,
__func__);
return 0;
}
/* environment buffer */
env = kzalloc(sizeof(struct kobj_uevent_env),
GFP_KERNEL);
if (!env)
return -ENOMEM;
/* complete object path */
devpath = kobject_get_path(kobj, GFP_KERNEL);
if (!devpath) {
retval = -ENOENT;
goto exit;
}
/* default keys */
retval = add_uevent_var(env, "ACTION=%s", action_string);
if (retval)
goto exit;
retval = add_uevent_var(env, "DEVPATH=%s", devpath);
if (retval)
goto exit;
retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem);
if (retval)
goto exit;
/* keys passed in from the caller */
if (envp_ext) {
for (i = 0; envp_ext[i]; i++) {
retval = add_uevent_var(env, "%s", envp_ext[i]);//将我们设置的参数，添加到环境变量中去
if (retval)
goto exit;
}
}
/* let the kset specific function add its stuff */
if (uevent_ops && uevent_ops->uevent) {
retval = uevent_ops->uevent(kset, kobj, env);
if (retval) {
pr_debug("kobject: '%s' (%p): %s: uevent() returned "
"%d\n", kobject_name(kobj), kobj,
__func__, retval);
goto exit;
}
}
/*
* Mark "add" and "remove" events in the object to ensure proper
* events to userspace during automatic cleanup. If the object did
* send an "add" event, "remove" will automatically generated by
* the core, if not already done by the caller.
*/
if (action == KOBJ_ADD)
kobj->state_add_uevent_sent = 1;
elseif (action == KOBJ_REMOVE)
kobj->state_remove_uevent_sent = 1;
/* we will send an event, so request a new sequence number */
spin_lock(&sequence_lock);
seq = ++uevent_seqnum;
spin_unlock(&sequence_lock);
retval = add_uevent_var(env, "SEQNUM=%llu", (unsignedlonglong)seq);
if (retval)
goto exit;
#if defined(CONFIG_NET)
/* send netlink message */
mutex_lock(&uevent_sock_mutex);
list_for_each_entry(ue_sk, &uevent_sock_list, list) {
struct sock *uevent_sock = ue_sk->sk;
struct sk_buff *skb;
size_t len;
/* allocate message with the maximum possible size */
len = strlen(action_string) + strlen(devpath) + 2;
skb = alloc_skb(len + env->buflen, GFP_KERNEL);
if (skb) {
char *scratch;
/* add header */
scratch = skb_put(skb, len);
sprintf(scratch, "%s@%s", action_string, devpath);
/* copy keys to our continuous event payload buffer */
for (i = 0; i < env->envp_idx; i++) {
len = strlen(env->envp[i]) + 1;
scratch = skb_put(skb, len);
strcpy(scratch, env->envp[i]);
}
NETLINK_CB(skb).dst_group = 1;
retval = netlink_broadcast_filtered(uevent_sock, skb,
0, 1, GFP_KERNEL,
kobj_bcast_filter,
kobj);
/* ENOBUFS should be handled in userspace */
if (retval == -ENOBUFS)
retval = 0;
} else
retval = -ENOMEM;
}
mutex_unlock(&uevent_sock_mutex);
#endif
/* call uevent_helper, usually only enabled during early boot */
if (uevent_helper[0] && !kobj_usermode_filter(kobj)) {
char *argv [3];
argv [0] = uevent_helper;
argv [1] = (char *)subsystem;
argv [2] = NULL;
retval = add_uevent_var(env, "HOME=/");
if (retval)
goto exit;
retval = add_uevent_var(env,
"PATH=/sbin:/bin:/usr/sbin:/usr/bin");
if (retval)
goto exit;
retval = call_usermodehelper(argv[0], argv,
env->envp, UMH_WAIT_EXEC);
}
exit:
kfree(devpath);
kfree(env);
return retval;
}
EXPORT_SYMBOL_GPL(kobject_uevent_env);
看下如何将用户空间需要的参数添加到环境变量中去的？？
传进去需要的参数
add_uevent_var(env, "%s", envp_ext[i]);
**
* add_uevent_var - add key value string to the environment buffer
* @env: environment buffer structure
* @format: printf format for the key=value pair
*
* Returns 0 if environment variable was added successfully or -ENOMEM
* if no space was available.
*/
int add_uevent_var(struct kobj_uevent_env *env, constchar *format,
...)
{
va_list args;
int len;
if (env->envp_idx >= ARRAY_SIZE(env->envp))
{
WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
return -ENOMEM;
}
va_start(args, format);
len = vsnprintf(&env->buf[env->buflen],
sizeof(env->buf) - env->buflen,
format, args);
va_end(args);
if (len >= (sizeof(env->buf)
- env->buflen)) {
WARN(1, KERN_ERR "add_uevent_var: buffer size too small\n");
return -ENOMEM;
}
env->envp[env->envp_idx++] = &env->buf[env->buflen];
env->buflen += len + 1;
return 0;
}
EXPORT_SYMBOL_GPL(add_uevent_var);
上面的函数在将参数添加到环境变量中去，如果添加添加成功的话，那么就返回0
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