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Souce Code는 다음과 같다.

#include	<stdio.h>
#include	<string.h>	/* for memset */
#include	<unistd.h>	/* for open/close .. */
#include	<fcntl.h>	/* for O_RDWR */
#include	<sys/ioctl.h>	/* for ioctl */
#include	<sys/mman.h>	/* for mmap */
#include	<linux/fb.h>	/* for fb_var_screeninfo, FBIOGET_VSCREENINFO */


#define	DEFAULT_FRAME_BUFFER_FILE "/dev/fb0"

typedef	struct
{
	int				Device;
  	void *				pFrameBuffer;
  	struct	fb_var_screeninfo	var;
	struct	fb_fix_screeninfo	fix;
} FrameBufferContext_t;


void	draw_pixel(	FrameBufferContext_t *pFrameBufferContext,
			unsigned long X,
			unsigned long Y,
			unsigned long Color)
{
	void *	pFrameBuffer;

	pFrameBuffer = pFrameBufferContext->pFrameBuffer;
	if (pFrameBufferContext->var.bits_per_pixel == 8)
	{
		unsigned char *		p;

		pFrameBuffer += pFrameBufferContext->fix.line_length * Y;
		p = pFrameBuffer;
		p += X;

		*p = (unsigned char)Color;
	}
	else if (pFrameBufferContext->var.bits_per_pixel == 16)
	{
		unsigned short *	p;

		pFrameBuffer += pFrameBufferContext->fix.line_length * Y;
		p = pFrameBuffer;
		p += X;

		*p = (unsigned short)(((((Color >> 16) & 0xff) * 32 / 256) << 11) | ((((Color >> 8) & 0xff) * 64 / 256) << 5) | ((((Color >> 0) & 0xff) * 32 / 256) << 0));
	}
	else if (pFrameBufferContext->var.bits_per_pixel == 24)
	{
		unsigned char *		p;

		p = (unsigned char *)pFrameBuffer + pFrameBufferContext->fix.line_length * Y + 3 * X;

		*p++ = (unsigned char)Color;
		*p++ = (unsigned char)(Color >> 8);
		*p = (unsigned char)(Color >> 16);
	}
	else
	{
		unsigned long *		p;

		pFrameBuffer += pFrameBufferContext->fix.line_length * Y;
		p = pFrameBuffer;
		p += X;

		*p = Color;
	}
}


void	fill_screen(FrameBufferContext_t *pFrameBufferContext)
{
	unsigned long	x;
	unsigned long	y;
	unsigned long	h;
	unsigned long	w;

	h = pFrameBufferContext->var.yres;
	w = pFrameBufferContext->var.xres;
	for (y = 0; y < h; y++)
	{
		for (x = 0; x < w; x++)
		{
			if (x < 20 && y < 20)
			{
				draw_pixel(pFrameBufferContext, x, y, 0xffffff);
			}
			else if (x < 20 && (y > 20 && y < h - 20))
			{
				draw_pixel(pFrameBufferContext, x, y, 0xff);
			}
			else if (y < 20 && (x > 20 && x < w - 20))
			{
				draw_pixel(pFrameBufferContext, x, y, 0xff00);
			}
			else if (x > w - 20 && (y > 20 && y < h - 20))
			{
				draw_pixel(pFrameBufferContext, x, y, 0xff0000);
			}
			else if (y > h - 20 && (x > 20 && x < w - 20))
			{
				draw_pixel(pFrameBufferContext, x, y, 0xffff00);
			}
			else if (x == 20 || x == w - 20 ||
					y == 20 || y == h - 20)
			{
				draw_pixel(pFrameBufferContext, x, y, 0xffffff);
			}
			else if (x == y || w - x == h - y)
			{
				draw_pixel(pFrameBufferContext, x, y, 0xff00ff);
			}
			else if (w - x == y || x == h - y)
			{
				draw_pixel(pFrameBufferContext, x, y, 0x00ffff);
			}

			else if (x > 20 && y > 20 && x < w - 20 && y < h - 20)
			{
				int t = x * 3 / w;
				unsigned r = 0, g = 0, b = 0;
				unsigned c;
				if (pFrameBufferContext->var.bits_per_pixel == 16)
				{
					if (t == 0)
					{
						b = (y % 32) * 256 / 32;
					}
					else if (t == 1)
					{
						g = (y % 64) * 256 / 64;
					}
					else if (t == 2)
					{
						r = (y % 32) * 256 / 32;
					}
				}
				else
				{
					if (t == 0)
					{
						b = (y % 256);
					}
					else if (t == 1)
					{
						g = (y % 256);
					}
					else if (t == 2)
					{
						r = (y % 256);
					}
				}
				c = (b << 16) | (g << 8) | (r << 0);
				draw_pixel(pFrameBufferContext, x, y, c);
			}
			else
			{
				draw_pixel(pFrameBufferContext, x, y, 0);
			}
		}
	}
}

void	clear_area(	FrameBufferContext_t *pFrameBufferContext,
			unsigned long X,
			unsigned long Y,
			unsigned long W,
			unsigned long H)
{
	unsigned long	AddressOffsetForH;
	unsigned long	CountForH;
	unsigned char *	pFrameBuffer;

	pFrameBuffer = (unsigned char *)pFrameBufferContext->pFrameBuffer;

	for (CountForH = 0; CountForH < H; CountForH++)
	{
		AddressOffsetForH = (X + pFrameBufferContext->var.xoffset) * (pFrameBufferContext->var.bits_per_pixel / 8) + (Y + CountForH + pFrameBufferContext->var.yoffset) * pFrameBufferContext->fix.line_length;

		memset(pFrameBuffer + AddressOffsetForH, 0, W * pFrameBufferContext->var.bits_per_pixel / 8);
	}
}


int	device_open_mode(FrameBufferContext_t *pFrameBufferContext, int BitPerPixel)
{
	pFrameBufferContext->Device = open(DEFAULT_FRAME_BUFFER_FILE, O_RDWR);
	if(pFrameBufferContext->Device < 0)
	{
		printf("Faile to open : %s \n", DEFAULT_FRAME_BUFFER_FILE);
		return	-1;
	}

	if(ioctl(pFrameBufferContext->Device, FBIOGET_VSCREENINFO, &pFrameBufferContext->var) < 0)
	{
		printf("fbdev ioctl(VSCREENINFO)\n");
		close(pFrameBufferContext->Device);
		return	-1;
	}

	if(ioctl(pFrameBufferContext->Device, FBIOGET_FSCREENINFO, &pFrameBufferContext->fix) < 0)
	{
		printf("fbdev ioctl(FSCREENINFO)\n");
		close(pFrameBufferContext->Device);
		return	-1;
	}

	if(pFrameBufferContext->var.bits_per_pixel != BitPerPixel)
	{
		pFrameBufferContext->var.bits_per_pixel = BitPerPixel;
		if(ioctl(pFrameBufferContext->Device, FBIOPUT_VSCREENINFO, &pFrameBufferContext->var) < 0)
		{
			printf("fbdev ioctl(PUT)\n");
			close(pFrameBufferContext->Device);
			return	-1;
		}
	}

	return	0;
}


int	device_open(FrameBufferContext_t *pFrameBufferContext)
{
	if(device_open_mode(pFrameBufferContext, 8) != 0)
	{
		printf("Faile to open with 8bit: %s \n", DEFAULT_FRAME_BUFFER_FILE);
		return	-1;
	}
	close(pFrameBufferContext->Device);

	if(device_open_mode(pFrameBufferContext, 24) != 0)
	{
		printf("Faile to open with 24bit: %s \n", DEFAULT_FRAME_BUFFER_FILE);
		return	-1;
	}

	printf("x-resolution : %d\n", pFrameBufferContext->var.xres);
	printf("y-resolution : %d\n", pFrameBufferContext->var.yres);
	printf("x-resolution(virtual) : %d\n", pFrameBufferContext->var.xres_virtual);
	printf("y-resolution(virtual) : %d\n", pFrameBufferContext->var.yres_virtual);
	printf("bpp : %d\n", pFrameBufferContext->var.bits_per_pixel);
	printf("length of frame buffer memory : %d\n", pFrameBufferContext->fix.smem_len);

	return	0;
}


int	main()
{
	FrameBufferContext_t	FrameBufferContext;
	int			Error;

	printf("Opening frame buffer device `%s'\n", DEFAULT_FRAME_BUFFER_FILE);

	if(device_open(&FrameBufferContext) != 0)
	{
		printf("Fail to Device Open\n");
		return	0;
	}

	FrameBufferContext.pFrameBuffer = mmap(0,
			FrameBufferContext.var.yres_virtual * FrameBufferContext.fix.line_length,
			PROT_WRITE | PROT_READ,
			MAP_SHARED,
			FrameBufferContext.Device,
			0);

	if(FrameBufferContext.pFrameBuffer == MAP_FAILED)
	{
		printf("Frame buffer MAP fail !\n");
		close(FrameBufferContext.Device);
		return	0;
	}

/* Display pattern to screen */
	fill_screen(&FrameBufferContext);

/* End of... */
	munmap(	FrameBufferContext.pFrameBuffer,
			FrameBufferContext.var.yres_virtual * FrameBufferContext.fix.line_length);


	close(FrameBufferContext.Device);
	return	0;
}

test_app_002.zip

아래와 같이 컴파일 한다.

stephanos@stephanos-VirtualBox:~/VI/App$ /home/stephanos/VI/gcc-linaro-6.2.1-2016.11-x86_64_arm-linux-gnueabihf/bin/arm-linux-gnueabihf-gcc -o test test.c

NFS에 위에서 만들어진 test를 복사한다. Target Board를 NFS로 부팅한다.

로그인 후 아래와 같이 실행한다.