fw_env.c

	if (mode == O_RDWR) {
		if (HaveRedundEnv) {
			/* switch to next partition for writing */
			dev_target = !dev_current;
			/* dev_target: fd_target, erase_target */
			fd_target = open (DEVNAME (dev_target), mode);
			if (fd_target < 0) {
				fprintf (stderr,
					 "Can't open %s: %s\n",
					 DEVNAME (dev_target),
					 strerror (errno));
				rc = -1;
				goto exit;
			}
		} else {
			dev_target = dev_current;
			fd_target = fd_current;
		}

		rc = flash_write (fd_current, fd_target, dev_target);

		if (HaveRedundEnv) {
			if (close (fd_target)) {
				fprintf (stderr,
					"I/O error on %s: %s\n",
					DEVNAME (dev_target),
					strerror (errno));
				rc = -1;
			}
		}
	} else {
		rc = flash_read (fd_current);
	}

exit:
	if (close (fd_current)) {
		fprintf (stderr,
			 "I/O error on %s: %s\n",
			 DEVNAME (dev_current), strerror (errno));
		return -1;
	}

	return rc;
}

/*
 * s1 is either a simple 'name', or a 'name=value' pair.
 * s2 is a 'name=value' pair.
 * If the names match, return the value of s2, else NULL.
 */

static char *envmatch (char * s1, char * s2)
{

	while (*s1 == *s2++)
		if (*s1++ == '=')
			return s2;
	if (*s1 == '\0' && *(s2 - 1) == '=')
		return s2;
	return NULL;
}

/*
 * Prevent confusion if running from erased flash memory
 */
int fw_env_open(void)
{
	int crc0, crc0_ok;
	char flag0;
	void *addr0;

	int crc1, crc1_ok;
	char flag1;
	void *addr1;

	struct env_image_single *single;
	struct env_image_redundant *redundant;

	if (parse_config ())		/* should fill envdevices */
		return -1;

	addr0 = calloc (1, CONFIG_ENV_SIZE);
	if (addr0 == NULL) {
		fprintf (stderr,
			"Not enough memory for environment (%ld bytes)\n",
			CONFIG_ENV_SIZE);
		return -1;
	}

	/* read environment from FLASH to local buffer */
	environment.image = addr0;

	if (HaveRedundEnv) {
		redundant = addr0;
		environment.crc		= &redundant->crc;
		environment.flags	= &redundant->flags;
		environment.data	= redundant->data;
	} else {
		single = addr0;
		environment.crc		= &single->crc;
		environment.flags	= NULL;
		environment.data	= single->data;
	}

	dev_current = 0;
	if (flash_io (O_RDONLY))
		return -1;

	crc0 = crc32 (0, (uint8_t *) environment.data, ENV_SIZE);
	crc0_ok = (crc0 == *environment.crc);
	if (!HaveRedundEnv) {
		if (!crc0_ok) {
			fprintf (stderr,
				"Warning: Bad CRC, using default environment\n");
			memcpy(environment.data, default_environment, sizeof default_environment);
		}
	} else {
		flag0 = *environment.flags;

		dev_current = 1;
		addr1 = calloc (1, CONFIG_ENV_SIZE);
		if (addr1 == NULL) {
			fprintf (stderr,
				"Not enough memory for environment (%ld bytes)\n",
				CONFIG_ENV_SIZE);
			return -1;
		}
		redundant = addr1;

		/*
		 * have to set environment.image for flash_read(), careful -
		 * other pointers in environment still point inside addr0
		 */
		environment.image = addr1;
		if (flash_io (O_RDONLY))
			return -1;

		/* Check flag scheme compatibility */
		if (DEVTYPE(dev_current) == MTD_NORFLASH &&
		    DEVTYPE(!dev_current) == MTD_NORFLASH) {
			environment.flag_scheme = FLAG_BOOLEAN;
		} else if (DEVTYPE(dev_current) == MTD_NANDFLASH &&
			   DEVTYPE(!dev_current) == MTD_NANDFLASH) {
			environment.flag_scheme = FLAG_INCREMENTAL;
		} else {
			fprintf (stderr, "Incompatible flash types!\n");
			return -1;
		}

		crc1 = crc32 (0, (uint8_t *) redundant->data, ENV_SIZE);
		crc1_ok = (crc1 == redundant->crc);
		flag1 = redundant->flags;

		if (crc0_ok && !crc1_ok) {
			dev_current = 0;
		} else if (!crc0_ok && crc1_ok) {
			dev_current = 1;
		} else if (!crc0_ok && !crc1_ok) {
			fprintf (stderr,
				"Warning: Bad CRC, using default environment\n");
			memcpy (environment.data, default_environment,
				sizeof default_environment);
			dev_current = 0;
		} else {
			switch (environment.flag_scheme) {
			case FLAG_BOOLEAN:
				if (flag0 == active_flag &&
				    flag1 == obsolete_flag) {
					dev_current = 0;
				} else if (flag0 == obsolete_flag &&
					   flag1 == active_flag) {
					dev_current = 1;
				} else if (flag0 == flag1) {
					dev_current = 0;
				} else if (flag0 == 0xFF) {
					dev_current = 0;
				} else if (flag1 == 0xFF) {
					dev_current = 1;
				} else {
					dev_current = 0;
				}
				break;
			case FLAG_INCREMENTAL:
				if ((flag0 == 255 && flag1 == 0) ||
				    flag1 > flag0)
					dev_current = 1;
				else if ((flag1 == 255 && flag0 == 0) ||
					 flag0 > flag1)
					dev_current = 0;
				else /* flags are equal - almost impossible */
					dev_current = 0;
				break;
			default:
				fprintf (stderr, "Unknown flag scheme %u \n",
					 environment.flag_scheme);
				return -1;
			}
		}

		/*
		 * If we are reading, we don't need the flag and the CRC any
		 * more, if we are writing, we will re-calculate CRC and update
		 * flags before writing out
		 */
		if (dev_current) {
			environment.image	= addr1;
			environment.crc		= &redundant->crc;
			environment.flags	= &redundant->flags;
			environment.data	= redundant->data;
			free (addr0);
		} else {
			environment.image	= addr0;
			/* Other pointers are already set */
			free (addr1);
		}
	}
	return 0;
}


static int parse_config ()
{
	struct stat st;

#if defined(CONFIG_FILE)
	/* Fills in DEVNAME(), ENVSIZE(), DEVESIZE(). Or don't. */
	if (get_config (CONFIG_FILE)) {
		fprintf (stderr,
			"Cannot parse config file: %s\n", strerror (errno));
		return -1;
	}
#else
	strcpy (DEVNAME (0), DEVICE1_NAME);
	DEVOFFSET (0) = DEVICE1_OFFSET;
	ENVSIZE (0) = ENV1_SIZE;
	DEVESIZE (0) = DEVICE1_ESIZE;
	ENVSECTORS (0) = DEVICE1_ENVSECTORS;
#ifdef HAVE_REDUND
	strcpy (DEVNAME (1), DEVICE2_NAME);
	DEVOFFSET (1) = DEVICE2_OFFSET;
	ENVSIZE (1) = ENV2_SIZE;
	DEVESIZE (1) = DEVICE2_ESIZE;
	ENVSECTORS (1) = DEVICE2_ENVSECTORS;
	HaveRedundEnv = 1;
#endif
#endif
	if (stat (DEVNAME (0), &st)) {
		fprintf (stderr,
			"Cannot access MTD device %s: %s\n",
			DEVNAME (0), strerror (errno));
		return -1;
	}

	if (HaveRedundEnv && stat (DEVNAME (1), &st)) {
		fprintf (stderr,
			"Cannot access MTD device %s: %s\n",
			DEVNAME (1), strerror (errno));
		return -1;
	}
	return 0;
}

#if defined(CONFIG_FILE)
static int get_config (char *fname)
{
	FILE *fp;
	int i = 0;
	int rc;
	char dump[128];

	fp = fopen (fname, "r");
	if (fp == NULL)
		return -1;

	while (i < 2 && fgets (dump, sizeof (dump), fp)) {
		/* Skip incomplete conversions and comment strings */
		if (dump[0] == '#')
			continue;

		rc = sscanf (dump, "%s %lx %lx %lx %lx",
			     DEVNAME (i),
			     &DEVOFFSET (i),
			     &ENVSIZE (i),
			     &DEVESIZE (i),
			     &ENVSECTORS (i));

		if (rc < 4)
			continue;

		if (rc < 5)
			/* Default - 1 sector */
			ENVSECTORS (i) = 1;

		i++;
	}
	fclose (fp);

	HaveRedundEnv = i - 1;
	if (!i) {			/* No valid entries found */
		errno = EINVAL;
		return -1;
	} else
		return 0;
}
#endif