linux设备模型深探(5)

/* 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, \

if (retval)

goto exit;

retval = add_uevent_var(env, \

if (retval)

goto exit;

retval = add_uevent_var(env, \

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, envp_ext[i]);

if (retval)

goto exit;

}

}

接下来,就应该设置为调用hotplug设置环境变量了.首先,分配一个struct kobj_uevent_env结构用来存放环境变量的值.然后调用kobject_get_path()用来获得引起事件的kobject在sysfs中的路径.再调用add_uevent_var()将动作代表的字串,kobject路径,子系统名称填充到struct kobj_uevent_env中,如果有指定环境变量,也将其添加进去. kobject_get_path()和add_uevent_var()都比较简单.这里不再详细分析了.请自行查看源代码

/* 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(\

\

__FUNCTION__, retval);

goto exit;

}

}

/*

* Mark \

* events to userspace during automatic cleanup. If the object did

* send an \

* the core, if not already done by the caller.

*/

if (action == KOBJ_ADD)

kobj->state_add_uevent_sent = 1;

else if (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, \

if (retval)

goto exit;

在这里还会调用kobject->kset-> uevent_ops->uevent().让产生事件的kobject添加环境变量.最

后将事件序列添加到环境变量中去.

#if defined(CONFIG_NET)

/* send netlink message */

if (uevent_sock) {

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, \

/* 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;

netlink_broadcast(uevent_sock, skb, 0, 1, GFP_KERNEL);

}

}

#endif

/* 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;

retval = add_uevent_var(env, \

if (retval)

goto exit;

retval = add_uevent_var(env,

\

if (retval)