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POClarifying on function calling
 

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    <p>I am under learning of Android source code. And I want to know that how the lower level functions are getting calling from application.</p> <p>While learning in this aspect, now I am in the struggle to understand one file which I have given below:</p> <pre><code>static int open_lights(const struct hw_module_t* module, char const* name, struct hw_device_t** device) { int (*set_light)(struct light_device_t* dev, struct light_state_t const* state); if (0 == strcmp(LIGHT_ID_BACKLIGHT, name)) { set_light = set_light_backlight; } else if (0 == strcmp(LIGHT_ID_KEYBOARD, name)) { set_light = set_light_keyboard; } else if (0 == strcmp(LIGHT_ID_BUTTONS, name)) { set_light = set_light_buttons; } else if (0 == strcmp(LIGHT_ID_BATTERY, name)) { set_light = set_light_battery; } else if (0 == strcmp(LIGHT_ID_NOTIFICATIONS, name)) { set_light = set_light_notification; } else if (0 == strcmp(LIGHT_ID_ATTENTION, name)) { set_light = set_light_attention; } else { return -EINVAL; } pthread_once(&amp;g_init, init_globals); struct light_device_t *dev = malloc(sizeof(struct light_device_t)); memset(dev, 0, sizeof(*dev)); dev-&gt;common.tag = HARDWARE_DEVICE_TAG; dev-&gt;common.version = 0; dev-&gt;common.module = (struct hw_module_t*)module; dev-&gt;common.close = (int (*)(struct hw_device_t*))close_lights; dev-&gt;set_light = set_light; *device = (struct hw_device_t*)dev; return 0; } set_light_backlight(struct light_device_t* dev, struct light_state_t const* state) { int err = 0; int brightness = rgb_to_brightness(state); pthread_mutex_lock(&amp;g_lock); err = write_int(LCD_FILE, brightness); pthread_mutex_unlock(&amp;g_lock); return err; } </code></pre> <p>My questions are:</p> <ol> <li>What is the meaning of <code>int (*set_light)(struct light_device_t* dev, struct light_state_t const* state);</code> this statement?</li> <li>We are just assigning <code>set_light_backlight</code> to <code>set_light</code>. Then how can <code>set_light_backlight(struct light_device_t* dev, struct light_state_t const* state)</code> function get called?</li> </ol>
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    1. USJonathan Leffler
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    1. COI don't often see 'c' and 'android' tagged in the same question.
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    2. COYou should at least learn the basics of C and then come back to ask specific questions.
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      1. USSimon
    3. CO@Simon ok sir. I knew somewhat in C. But I do not know much about pointer. Thank you.
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