[移动开发]Android开机画面显示

一、fbcon
fbcon是帧缓冲区控制台，它在帧缓冲系统初始化时初始化：

static int __init
fbmem_init(void)
{
	...
	fb_console_init();

	return 0;

}

void __init fb_console_init(void)
{
	int i;

	console_lock();
	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;

	fbcon_start();
	console_unlock();
}

static void fbcon_start(void)
{
	WARN_CONSOLE_UNLOCKED();

#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DEFERRED_TAKEOVER
	if (conswitchp != &dummy_con)
		deferred_takeover = false;

	if (deferred_takeover) {
		fbcon_output_nb.notifier_call = fbcon_output_notifier;
		dummycon_register_output_notifier(&fbcon_output_nb);
		return;
	}
#endif

	if (num_registered_fb) {
		int i;

		for_each_registered_fb(i) {
			info_idx = i;
			break;
		}

		do_fbcon_takeover(0);
	}
}

在帧缓冲硬件设备注册的函数中，调用fbcon_fb_registered来处理

static int do_register_framebuffer(struct fb_info *fb_info)
{

#ifdef CONFIG_GUMSTIX_AM200EPD
	{
		struct fb_event event;
		event.info = fb_info;
		fb_notifier_call_chain(FB_EVENT_FB_REGISTERED, &event);
	}
#endif

	if (!lockless_register_fb)
		console_lock();
	else
		atomic_inc(&ignore_console_lock_warning);
	lock_fb_info(fb_info);
	ret = fbcon_fb_registered(fb_info);
	unlock_fb_info(fb_info);

	if (!lockless_register_fb)
		console_unlock();
	else
		atomic_dec(&ignore_console_lock_warning);
	return ret;
}

/* called with console_lock held */
int fbcon_fb_registered(struct fb_info *info)
{
	int ret = 0, i, idx;

	WARN_CONSOLE_UNLOCKED();

	idx = info->node;
	fbcon_select_primary(info);

	if (deferred_takeover) {
		pr_info("fbcon: Deferring console take-over\n");
		return 0;
	}

	if (info_idx == -1) {
		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;
}

假设系统只有一个帧缓冲硬件设备，那么当它被注册时，全局变量info_idx 的值就为-1，当在全局数组con2fb_map_boot中发现有一个控制台的编号与这个帧缓冲硬件设备编号idx对应时，接下来会调用do_fbcon_takeover来设置系统所使用的控制台。

static int do_fbcon_takeover(int show_logo)
{
	int err, i;

	if (!num_registered_fb)
		return -ENODEV;

	if (!show_logo)
		logo_shown = FBCON_LOGO_DONTSHOW;

	for (i = first_fb_vc; i <= last_fb_vc; i++)
		con2fb_map[i] = info_idx;

	err = do_take_over_console(&fb_con, first_fb_vc, last_fb_vc,
				fbcon_is_default);

	if (err) {
		for (i = first_fb_vc; i <= last_fb_vc; i++)
			con2fb_map[i] = -1;
		info_idx = -1;
	} else {
		fbcon_has_console_bind = 1;
	}

	return err;
}

该函数实际是向系统注册一系列回调函数

/*
 *  The console `switch' structure for the frame buffer based console
 */

static const struct consw fb_con = {
	.owner			= THIS_MODULE,
	.con_startup 		= fbcon_startup,
	.con_init 		= fbcon_init,
	.con_deinit 		= fbcon_deinit,
	.con_clear 		= fbcon_clear,
	.con_putc 		= fbcon_putc,
	.con_putcs 		= fbcon_putcs,
	.con_cursor 		= fbcon_cursor,
	.con_scroll 		= fbcon_scroll,
	.con_switch 		= fbcon_switch,
	.con_blank 		= fbcon_blank,
	.con_font_set 		= fbcon_set_font,
	.con_font_get 		= fbcon_get_font,
	.con_font_default	= fbcon_set_def_font,
	.con_font_copy 		= fbcon_copy_font,
	.con_set_palette 	= fbcon_set_palette,
	.con_scrolldelta 	= fbcon_scrolldelta,
	.con_set_origin 	= fbcon_set_origin,
	.con_invert_region 	= fbcon_invert_region,
	.con_screen_pos 	= fbcon_screen_pos,
	.con_getxy 		= fbcon_getxy,
	.con_resize             = fbcon_resize,
	.con_debug_enter	= fbcon_debug_enter,
	.con_debug_leave	= fbcon_debug_leave,
};

我们主要关注fbcon_init和fbcon_switch，系统就是通过它来初始化和切换控制台的。在初始化的过程中，会决定是否准备第一个开机画面的内容，而在切换控制台的过程中，会决定是否显示第一个开机画面的内容。

static void fbcon_init(struct vc_data *vc, int init)
{
	struct fb_info *info;
	struct fbcon_ops *ops;
	struct vc_data **default_mode = vc->vc_display_fg;
	struct vc_data *svc = *default_mode;
	struct fbcon_display *t, *p = &fb_display[vc->vc_num];
	int logo = 1, new_rows, new_cols, rows, cols, charcnt = 256;
	int cap, ret;

	...
	if (logo_shown < 0 && console_loglevel <= CONSOLE_LOGLEVEL_QUIET)
		logo_shown = FBCON_LOGO_DONTSHOW;

	if (vc != svc || logo_shown == FBCON_LOGO_DONTSHOW ||
	    (info->fix.type == FB_TYPE_TEXT))
		logo = 0;

	...

	if (logo)
		fbcon_prepare_logo(vc, info, cols, rows, new_cols, new_rows);


	ops->p = &fb_display[fg_console];
}

当logo的值为1时，调用fbcon_prepare_logo来准备要显示的第一个画面内容

#ifdef MODULE
static void fbcon_prepare_logo(struct vc_data *vc, struct fb_info *info,
			       int cols, int rows, int new_cols, int new_rows)
{
	logo_shown = FBCON_LOGO_DONTSHOW;
}
#else
static void fbcon_prepare_logo(struct vc_data *vc, struct fb_info *info,
			       int cols, int rows, int new_cols, int new_rows)
{
	/* Need to make room for the logo */
	struct fbcon_ops *ops = info->fbcon_par;
	int cnt, erase = vc->vc_video_erase_char, step;
	unsigned short *save = NULL, *r, *q;
	int logo_height;

	if (info->fbops->owner) {
		logo_shown = FBCON_LOGO_DONTSHOW;
		return;
	}

	/*
	 * remove underline attribute from erase character
	 * if black and white framebuffer.
	 */
	if (fb_get_color_depth(&info->var, &info->fix) == 1)
		erase &= ~0x400;
	logo_height = fb_prepare_logo(info, ops->rotate);
	logo_lines = DIV_ROUND_UP(logo_height, vc->vc_font.height);
	q = (unsigned short *) (vc->vc_origin +
				vc->vc_size_row * rows);
	step = logo_lines * cols;
	for (r = q - logo_lines * cols; r < q; r++)
		if (scr_readw(r) != vc->vc_video_erase_char)
			break;
	if (r != q && new_rows >= rows + logo_lines) {
		save = kmalloc(array3_size(logo_lines, new_cols, 2),
			       GFP_KERNEL);
		if (save) {
			int i = cols < new_cols ? cols : new_cols;
			scr_memsetw(save, erase, logo_lines * new_cols * 2);
			r = q - step;
			for (cnt = 0; cnt < logo_lines; cnt++, r += i)
				scr_memcpyw(save + cnt * new_cols, r, 2 * i);
			r = q;
		}
	}
	if (r == q) {
		/* We can scroll screen down */
		r = q - step - cols;
		for (cnt = rows - logo_lines; cnt > 0; cnt--) {
			scr_memcpyw(r + step, r, vc->vc_size_row);
			r -= cols;
		}
		if (!save) {
			int lines;
			if (vc->vc_y + logo_lines >= rows)
				lines = rows - vc->vc_y - 1;
			else
				lines = logo_lines;
			vc->vc_y += lines;
			vc->vc_pos += lines * vc->vc_size_row;
		}
	}
	scr_memsetw((unsigned short *) vc->vc_origin,
		    erase,
		    vc->vc_size_row * logo_lines);

	if (con_is_visible(vc) && vc->vc_mode == KD_TEXT) {
		fbcon_clear_margins(vc, 0);
		update_screen(vc);
	}

	if (save) {
		q = (unsigned short *) (vc->vc_origin +
					vc->vc_size_row *
					rows);
		scr_memcpyw(q, save, logo_lines * new_cols * 2);
		vc->vc_y += logo_lines;
		vc->vc_pos += logo_lines * vc->vc_size_row;
		kfree(save);
	}

	if (logo_shown == FBCON_LOGO_DONTSHOW)
		return;

	if (logo_lines > vc->vc_bottom) {
		logo_shown = FBCON_LOGO_CANSHOW;
		printk(KERN_INFO
		       "fbcon_init: disable boot-logo (boot-logo bigger than screen).\n");
	} else {
		logo_shown = FBCON_LOGO_DRAW;
		vc->vc_top = logo_lines;
	}
}
#endif /* MODULE */

通过调用fb_prepare_logo来准备要显示的第一个画面

int fb_prepare_logo(struct fb_info *info, int rotate)
{
	int depth = fb_get_color_depth(&info->var, &info->fix);
	unsigned int yres;
	int height;

	memset(&fb_logo, 0, sizeof(struct logo_data));

	if (info->flags & FBINFO_MISC_TILEBLITTING ||
	    info->fbops->owner)
		return 0;


	/* Return if no suitable logo was found */
	fb_logo.logo = fb_find_logo(depth);


}

const struct linux_logo * __ref fb_find_logo(int depth)
{
	const struct linux_logo *logo = NULL;

	if (nologo || logos_freed)
		return NULL;

	if (depth >= 1) {
#ifdef CONFIG_LOGO_LINUX_MONO
		/* Generic Linux logo */
		logo = &logo_linux_mono;
#endif
#ifdef CONFIG_LOGO_SUPERH_MONO
		/* SuperH Linux logo */
		logo = &logo_superh_mono;
#endif
	}
	
	if (depth >= 4) {
#ifdef CONFIG_LOGO_LINUX_VGA16
		/* Generic Linux logo */
		logo = &logo_linux_vga16;
#endif
#ifdef CONFIG_LOGO_SUPERH_VGA16
		/* SuperH Linux logo */
		logo = &logo_superh_vga16;
#endif
	}
	
	if (depth >= 8) {
#ifdef CONFIG_LOGO_LINUX_CLUT224
		/* Generic Linux logo */
		logo = &logo_linux_clut224;
#endif
#ifdef CONFIG_LOGO_DEC_CLUT224
		/* DEC Linux logo on MIPS/MIPS64 or ALPHA */
		logo = &logo_dec_clut224;
#endif
#ifdef CONFIG_LOGO_MAC_CLUT224
		/* Macintosh Linux logo on m68k */
		if (MACH_IS_MAC)
			logo = &logo_mac_clut224;
#endif
#ifdef CONFIG_LOGO_PARISC_CLUT224
		/* PA-RISC Linux logo */
		logo = &logo_parisc_clut224;
#endif
#ifdef CONFIG_LOGO_SGI_CLUT224
		/* SGI Linux logo on MIPS/MIPS64 */
		logo = &logo_sgi_clut224;
#endif
#ifdef CONFIG_LOGO_SUN_CLUT224
		/* Sun Linux logo */
		logo = &logo_sun_clut224;
#endif
#ifdef CONFIG_LOGO_SUPERH_CLUT224
		/* SuperH Linux logo */
		logo = &logo_superh_clut224;
#endif
	}
	return logo;
}

这一步执行完成之后，第一个开机画面的图形就保存在fbmem的全局变量fb_logo的成员变量logo中了，接下来系统就会执行切换控制台的操作，系统会执行fbcon_switch函数
static int fbcon_switch(struct vc_data *vc)
{
…
if (logo_shown == FBCON_LOGO_DRAW) {

	logo_shown = fg_console;
	/* This is protected above by initmem_freed */
	fb_show_logo(info, ops->rotate);
	update_region(vc,
		      vc->vc_origin + vc->vc_size_row * vc->vc_top,
		      vc->vc_size_row * (vc->vc_bottom -
					 vc->vc_top) / 2);
	return 0;
}
return 1;

}
调用fb_show_logo来显示第一个开机界面

int fb_show_logo(struct fb_info *info, int rotate)
{
	int y;

	y = fb_show_logo_line(info, rotate, fb_logo.logo, 0,
			      num_online_cpus());
	y = fb_show_extra_logos(info, y, rotate);

	return y;
}

static int fb_show_logo_line(struct fb_info *info, int rotate,
			     const struct linux_logo *logo, int y,
			     unsigned int n)
{
	...

	fb_do_show_logo(info, &image, rotate, n);

	kfree(palette);
	if (saved_pseudo_palette != NULL)
		info->pseudo_palette = saved_pseudo_palette;
	kfree(logo_new);
	kfree(logo_rotate);
	return image.dy + logo->height;
}

该函数将linux_logo的数据转换为fb_image结构体的图形，调用fb_do_show_logo

static void fb_do_show_logo(struct fb_info *info, struct fb_image *image,
			    int rotate, unsigned int num)
{
	unsigned int x;

	if (image->width > info->var.xres || image->height > info->var.yres)
		return;

	if (rotate == FB_ROTATE_UR) {
		for (x = 0;
		     x < num && image->dx + image->width <= info->var.xres;
		     x++) {
			info->fbops->fb_imageblit(info, image);
			image->dx += image->width + 8;
		}
	} else if (rotate == FB_ROTATE_UD) {
		u32 dx = image->dx;

		for (x = 0; x < num && image->dx <= dx; x++) {
			info->fbops->fb_imageblit(info, image);
			image->dx -= image->width + 8;
		}
	} else if (rotate == FB_ROTATE_CW) {
		for (x = 0;
		     x < num && image->dy + image->height <= info->var.yres;
		     x++) {
			info->fbops->fb_imageblit(info, image);
			image->dy += image->height + 8;
		}
	} else if (rotate == FB_ROTATE_CCW) {
		u32 dy = image->dy;

		for (x = 0; x < num && image->dy <= dy; x++) {
			info->fbops->fb_imageblit(info, image);
			image->dy -= image->height + 8;
		}
	}
}

回调函数fb_imageblit就是用来在指定的帧缓冲硬件设备渲染图像

struct fb_ops {
	/* open/release and usage marking */
	struct module *owner;
	int (*fb_open)(struct fb_info *info, int user);
	int (*fb_release)(struct fb_info *info, int user);

	/* For framebuffers with strange non linear layouts or that do not
	 * work with normal memory mapped access
	 */
	ssize_t (*fb_read)(struct fb_info *info, char __user *buf,
			   size_t count, loff_t *ppos);
	ssize_t (*fb_write)(struct fb_info *info, const char __user *buf,
			    size_t count, loff_t *ppos);

	/* checks var and eventually tweaks it to something supported,
	 * DO NOT MODIFY PAR */
	int (*fb_check_var)(struct fb_var_screeninfo *var, struct fb_info *info);

	/* set the video mode according to info->var */
	int (*fb_set_par)(struct fb_info *info);

	/* set color register */
	int (*fb_setcolreg)(unsigned regno, unsigned red, unsigned green,
			    unsigned blue, unsigned transp, struct fb_info *info);

	/* set color registers in batch */
	int (*fb_setcmap)(struct fb_cmap *cmap, struct fb_info *info);

	/* blank display */
	int (*fb_blank)(int blank, struct fb_info *info);

	/* pan display */
	int (*fb_pan_display)(struct fb_var_screeninfo *var, struct fb_info *info);

	/* Draws a rectangle */
	void (*fb_fillrect) (struct fb_info *info, const struct fb_fillrect *rect);
	/* Copy data from area to another */
	void (*fb_copyarea) (struct fb_info *info, const struct fb_copyarea *region);
	/* Draws a image to the display */
	void (*fb_imageblit) (struct fb_info *info, const struct fb_image *image);

	/* Draws cursor */
	int (*fb_cursor) (struct fb_info *info, struct fb_cursor *cursor);

	/* wait for blit idle, optional */
	int (*fb_sync)(struct fb_info *info);

	/* perform fb specific ioctl (optional) */
	int (*fb_ioctl)(struct fb_info *info, unsigned int cmd,
			unsigned long arg);

	/* Handle 32bit compat ioctl (optional) */
	int (*fb_compat_ioctl)(struct fb_info *info, unsigned cmd,
			unsigned long arg);

	/* perform fb specific mmap */
	int (*fb_mmap)(struct fb_info *info, struct vm_area_struct *vma);

	/* get capability given var */
	void (*fb_get_caps)(struct fb_info *info, struct fb_blit_caps *caps,
			    struct fb_var_screeninfo *var);

	/* teardown any resources to do with this framebuffer */
	void (*fb_destroy)(struct fb_info *info);

	/* called at KDB enter and leave time to prepare the console */
	int (*fb_debug_enter)(struct fb_info *info);
	int (*fb_debug_leave)(struct fb_info *info);
};