Framebuffer 驱动学习总结（二）---- Framebuffer模块初始化

static int __init  fbmem_init(void)
{
    proc_create("fb", 0, NULL, &fb_proc_fops);///向 proc 文件系统报告驱动状态和参数
    if (register_chrdev(FB_MAJOR,"fb",&fb_fops))///注册字符设备驱动，主设备号是29 
        printk("unable to get major %d for fb devs\n", FB_MAJOR);
    fb_class = class_create(THIS_MODULE, "graphics");///创建 /sys/class/graphics 设备类，配合 mdev生成设备文件
    if (IS_ERR(fb_class)) {
        printk(KERN_WARNING "Unable to create fb class; errno = %ld\n", PTR_ERR(fb_class));
        fb_class = NULL;
    }
    return 0;
}

static const struct file_operations fb_fops = {
    .owner =    THIS_MODULE,
    .read =        fb_read,
    .write =    fb_write,//二次拷贝
    .unlocked_ioctl = fb_ioctl,
#ifdef CONFIG_COMPAT
    .compat_ioctl = fb_compat_ioctl,
#endif
    .mmap =        fb_mmap,///映射,一次拷贝
    .open =        fb_open,
    .release =    fb_release,
#ifdef HAVE_ARCH_FB_UNMAPPED_AREA
    .get_unmapped_area = get_fb_unmapped_area,
#endif
#ifdef CONFIG_FB_DEFERRED_IO
    .fsync =    fb_deferred_io_fsync,
#endif
    .llseek =    default_llseek,
};

int register_framebuffer(struct fb_info *fb_info)
{
    int ret;

    mutex_lock(&registration_lock);
    ret = do_register_framebuffer(fb_info);
    mutex_unlock(&registration_lock);

    return ret;
}
EXPORT_SYMBOL(register_framebuffer);// 在内核的启动过程会被调用，以便执行注册帧缓冲区硬件设备的操作

static int do_register_framebuffer(struct fb_info *fb_info)
{
    int i, ret;
    struct fb_event event;
    struct fb_videomode mode;

    if (fb_check_foreignness(fb_info))
        return -ENOSYS;

    ret = do_remove_conflicting_framebuffers(fb_info->apertures,
                         fb_info->fix.id,
                         fb_is_primary_device(fb_info));
    if (ret)
        return ret;

    if (num_registered_fb == FB_MAX)//如果注册的帧缓冲设备超过了FB_MAX（目前定义为32），则返回为-ENXIO,注册成功则返回为0。
        return -ENXIO;

    num_registered_fb++;///已经注册了的帧缓冲区硬件设备个数
    for (i = 0 ; i < FB_MAX; i++)
        if (!registered_fb[i])///registered_fb[i]保存所有已经注册了的帧缓冲区硬件设备
            break;
    fb_info->node = i;
    atomic_set(&fb_info->count, 1);
    mutex_init(&fb_info->lock);
    mutex_init(&fb_info->mm_lock);

    fb_info->dev = device_create(fb_class, fb_info->device,///在/sys/grapics/下创建 fbx设备，用于设备文件的创建
                     MKDEV(FB_MAJOR, i), NULL, "fb%d", i);
    if (IS_ERR(fb_info->dev)) {
        /* Not fatal */
        printk(KERN_WARNING "Unable to create device for framebuffer %d; errno = %ld\n", i, PTR_ERR(fb_info->dev));
        fb_info->dev = NULL;
    } else
        fb_init_device(fb_info);

    if (fb_info->pixmap.addr == NULL) {
        fb_info->pixmap.addr = kmalloc(FBPIXMAPSIZE, GFP_KERNEL);
        if (fb_info->pixmap.addr) {
            fb_info->pixmap.size = FBPIXMAPSIZE;
            fb_info->pixmap.buf_align = 1;
            fb_info->pixmap.scan_align = 1;
            fb_info->pixmap.access_align = 32;
            fb_info->pixmap.flags = FB_PIXMAP_DEFAULT;
        }
    }    
    fb_info->pixmap.offset = 0;

    if (!fb_info->pixmap.blit_x)
        fb_info->pixmap.blit_x = ~(u32)0;

    if (!fb_info->pixmap.blit_y)
        fb_info->pixmap.blit_y = ~(u32)0;

    if (!fb_info->modelist.prev || !fb_info->modelist.next)
        INIT_LIST_HEAD(&fb_info->modelist);

    if (fb_info->skip_vt_switch)
        pm_vt_switch_required(fb_info->dev, false);
    else
        pm_vt_switch_required(fb_info->dev, true);

    fb_var_to_videomode(&mode, &fb_info->var);
    fb_add_videomode(&mode, &fb_info->modelist);
    registered_fb[i] = fb_info;

    event.info = fb_info;
    console_lock();
    if (!lock_fb_info(fb_info)) {
        console_unlock();
        return -ENODEV;
    }

    fb_notifier_call_chain(FB_EVENT_FB_REGISTERED, &event);///通知帧缓冲区控制台，有一个新的帧缓冲区设备被注册到内核中来了
    unlock_fb_info(fb_info);
    console_unlock();
    return 0;
}

static struct notifier_block fbcon_event_notifier = {
    .notifier_call    = fbcon_event_notify,
};
......
static int __init fb_console_init(void)//帧缓冲区控制台初始化
{
    int i;

    console_lock();
    fb_register_client(&fbcon_event_notifier);//调用fb_register_client来监听帧缓冲区硬件设备的注册事件，fbcon_event_notifier--->实现
    fbcon_device = device_create(fb_class, NULL, MKDEV(0, 0), NULL,
                     "fbcon");

    if (IS_ERR(fbcon_device)) {
        printk(KERN_WARNING "Unable to create device "
               "for fbcon; errno = %ld\n",
               PTR_ERR(fbcon_device));
        fbcon_device = NULL;
    } else
        fbcon_init_device();

    for (i = 0; i < MAX_NR_CONSOLES; i++)
        con2fb_map[i] = -1;

    console_unlock();
    fbcon_start();
    return 0;
}

static int fbcon_event_notify(struct notifier_block *self,
                  unsigned long action, void *data)
{
    struct fb_event *event = data;
    struct fb_info *info = event->info;
    struct fb_videomode *mode;
    struct fb_con2fbmap *con2fb;
    struct fb_blit_caps *caps;
    int idx, ret = 0;

    switch(action) {
        
        ......

    case FB_EVENT_FB_REGISTERED:
        ret = fbcon_fb_registered(info);///---> 帧缓冲区硬件设备的注册事件最终是由函数fbcon_fb_registered来处理的
        break;

        .......
    }
done:
    return ret;
}        

static int fbcon_fb_registered(struct fb_info *info)
{
    int ret = 0, i, idx;

    idx = info->node;
    fbcon_select_primary(info);///检查当前注册的帧缓冲区硬件设备是否是一个主帧缓冲区硬件设备,如果是的话，那么就将它的信息记录下来

    if (info_idx == -1) {///如果是的话，那么就将它的信息记录下来
        for (i = first_fb_vc; i <= last_fb_vc; i++) {
            if (con2fb_map_boot[i] == idx) {
                info_idx = idx;
                break;
            }
        }

        if (info_idx != -1)
            ret = do_fbcon_takeover(1);
    } else {
        for (i = first_fb_vc; i <= last_fb_vc; i++) {
            if (con2fb_map_boot[i] == idx)
                set_con2fb_map(i, idx, 0);
        }
    }

    return ret;
}