(read(cam_fp, g_yuv, width*height*bpp/8) < 0)의미를 알고

static inline void save_yuv(int width, int height, int bpp, int iter)에서
if (read(cam_fp, g_yuv, width*height*bpp/8) < 0) {
perror("read()");
}
라는 것이 있는데 무슨 의미인지??

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <ctype.h>
#include <errno.h>
#include <sys/mman.h>
#include <sys/time.h>
#include <sys/ioctl.h>

/* maximum */
#define CAM_WIDTH 720
#define CAM_HEIGHT 240

static int cam_fp = -1;

#include "userapp.h"
camif_param_t camif_cfg;

static unsigned char *g_yuv;

#define CODEC_NAME  "/dev/misc/codec"


void fmalloc(int size)
{
	unsigned int i=0;
	unsigned int *ptr32;

	g_yuv = (unsigned char*)malloc(size);
	if(!g_yuv)  {
		printf("Memory Allcation Failed \n");
		exit(1);
	}
	ptr32 = (unsigned int *)g_yuv;
	for (;i<size/4; i++)
		*ptr32++ = 0xff00ff00; /* Red */
}


static inline int cam_init(void)
{
	int dev_fp = -1;

	dev_fp = open(CODEC_NAME, O_RDWR);
	if (dev_fp < 0) {
		perror(CODEC_NAME);
		printf("Open Failed \n");
		return -1;
	}
	return dev_fp;
}

static inline void save_yuv(int width, int height, int bpp, int iter)
{
 	FILE *yuv_fp = NULL;
	char file_name[100];
	
	 /* read from device */
	if (read(cam_fp, g_yuv, width*height*bpp/8) < 0) {
		perror("read()");
	}

	if (bpp == 16 ) {
		sprintf(&file_name[0], "422X%d.yuv", iter);
		printf("422X%d.yuv", iter);
	}
	else { 
		sprintf(&file_name[0], "420X%d.yuv", iter);
		printf("420X%d.yuv\n", iter);
	}
	fflush(stdout);
	/* file create/open, note to "wb" */
	yuv_fp = fopen(&file_name[0], "wb");
	if (!yuv_fp) {
		perror(&file_name[0]);
	}
	fwrite(g_yuv, 1, width * height * bpp / 8, yuv_fp);
	fclose(yuv_fp);
}