Here are five possible code completions for the given function:

### Completion 1: Basic Setup
```c
static int edge_detector_setup(struct line *line,
                               struct gpio_v2_line_config *lc,
                               unsigned int line_idx, u64 edflags)
{
    /* Set up edge detection for the given line */
    lc->event = edflags;
    return 0;
}
```

### Completion 2: Error Handling
```c
static int edge_detector_setup(struct line *line,
                               struct gpio_v2_line_config *lc,
                               unsigned int line_idx, u64 edflags)
{
    if (!line || !lc) {
        return -EINVAL; /* Invalid argument */
    }

    /* Set up edge detection for the given line */
    lc->event = edflags;
    return 0;
}
```

### Completion 3: Line Configuration
```c
static int edge_detector_setup(struct line *line,
                               struct gpio_v2_line_config *lc,
                               unsigned int line_idx, u64 edflags)
{
    /* Configure the line for edge detection */
    lc->flags = GPIO_V2_LINE_FLAG_EDGE_RISING | GPIO_V2_LINE_FLAG_EDGE_FALLING;
    lc->event = edflags;
    return 0;
}
```

### Completion 4: Edge Detection Flags
```c
static int edge_detector_setup(struct line *line,
                               struct gpio_v2_line_config *lc,
                               unsigned int line_idx, u64 edflags)
{
    /* Set up edge detection flags */
    if (edflags & EDGE_RISING) {
        lc->event = GPIO_V2_LINE_EVENT_RISING_EDGE;
    } else if (edflags & EDGE_FALLING) {
        lc->event = GPIO_V2_LINE_EVENT_FALLING_EDGE;
    } else {
        return -EINVAL; /* Invalid edge detection flags */
    }

    return 0;
}
```

### Completion 5: Line Index Validation
```c
static int edge_detector_setup(struct line *line,
                               struct gpio_v2_line_config *lc,
                               unsigned int line_idx, u64 edflags)
{
    if (line_idx >= MAX_LINES) {
        return -EINVAL; /* Line index out of range */
    }

    /* Set up edge detection for the given line */
    lc->event = edflags;
    return 0;
}
```

Note: These completions are just examples and may not be suitable for your specific use case. You should adapt them to your needs and ensure they are correct and secure.