ueventd: problem loading deferred modules

[Frédéric Lord]

Hi,
I work on a device that has usb connectors and we used them to plugged usb wifi adapter.
The problem I have is that when I reboot the device and the usb wifi adapter is plugged, the kernel module is not loaded (rtl8192cu and is dependency in my case). I must unplugged and replugged the wifi adapter to make them load.

My custom device was started from nougat-x86 but we used it has a traditionnal Android device the most possible.
In devices.cpp file, in device_init() function, the handle_deferred_module_loading() is called after the coldboot and the deferred modules should be loaded in this function by iterating through deferred_module_loading_list. When this function function is called, the modules_aliases_map is always empty, so the deferred modules are never loaded. The kernel events are correctly received and they are added in the deferred_module_loading_list. Here a copy of this function:
static void handle_deferred_module_loading()
{
    /* try to read the module alias mapping if map is empty
     * if succeed, loading all the modules in the queue
     */
    if (!list_empty(&modules_aliases_map)) {
        struct listnode *node = NULL;
        struct listnode *next = NULL;
        struct module_alias_node *alias = NULL;

        list_for_each_safe(node, next, &deferred_module_loading_list) {
            alias = node_to_item(node, struct module_alias_node, list);

            if (alias && alias->pattern) {
                INFO("deferred loading of module for %s\n", alias->pattern);
                load_module_by_device_modalias(alias->pattern, false);
                free(alias->pattern);
                list_remove(node);
                free(alias);
            }
        }
    }
}

The modules_aliases_map is empty because it is filled by reading "/system/lib/modules/4.8.11-android-x86_64+/modules.alias" file, this file cannot be read because the system partition is not mounted at this time, it is mounted later in fs action.
If I modify handle_deferred_module_loading() like below to wait booting before loading deferred modules, the kernel wifi modules are loaded correctly with some others modules that was not loaded before:
static void handle_deferred_module_loading()
{
    pid_t pid = fork();
    if (pid != 0) {
        return;
    }

    if (list_empty(&modules_aliases_map)) {
        read_modules_aliases();
        read_modules_blacklist();
    }
    while (is_booting()) {
        usleep(100000);

        if (list_empty(&modules_aliases_map)) {
            read_modules_aliases();
            read_modules_blacklist();
        }
    }

    /* try to read the module alias mapping if map is empty
     * if succeed, loading all the modules in the queue
     */
    if (!list_empty(&modules_aliases_map)) {
        struct listnode *node = NULL;
        struct listnode *next = NULL;
        struct module_alias_node *alias = NULL;

        list_for_each_safe(node, next, &deferred_module_loading_list) {
            alias = node_to_item(node, struct module_alias_node, list);

            if (alias && alias->pattern) {
                INFO("deferred loading of module for %s\n", alias->pattern);
                load_module_by_device_modalias(alias->pattern, false);
                free(alias->pattern);
                list_remove(node);
                free(alias);
            }
        }
    }
    exit(0);
}

I tried to mount the system partition before "start ueventd" in init.rc with this line "mount ext4 /dev/block/mmcblk0p5 /system ro", but the partition didn't seem to be mounted.
I tried too to revert commit cfa5ded4b3bbec856a14544c06f3148046e7dcca to make ueventd.cpp and devices.cpp like in nougat-release branch, but that doesn't correct the problem.
Maybe I'm missing something.

In nougat-release branch, I didn't see reference to deferred modules, so I was wondering how in traditional Android device the deferred modules are loaded (if they are loaded)?
I would like to know if there is a better solution then modifying handle_deferred_module_loading() and if the change I made could break something?

[Tom Cherry]

handle_deferred_module_loading() and the like are vendor changes to init.  It would be best to ask this question to the vendor themselves.

Traditional Android devices do not have module loading capabilities in this way.  The kernel is either built monolithic with all modules included, init scripts could load the module via insmod, or a daemon may load the module.

Tom

[Satish Patel]

Hi,

Is it because firmware is not found before file system mount ? Could you get dmesg log to look further into this ?

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Regards,
satish patel