/*
 *  Amiga NVRAM tool
 *
 *  (C) Copyright 2009 Geert Uytterhoeven
 *
 *  This file is subject to the terms and conditions of the GNU General Public
 *  License.
 */

#include <fcntl.h>
#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define NVRAM_FILE	"/sys/devices/platform/rtc-rp5c01/nvram"

#define ARRAY_SIZE(a)	(sizeof(a) / sizeof((a)[0]))


static const char *program_name;

static const char *opt_nvram = NVRAM_FILE;
static _Bool opt_checksum;
static _Bool opt_quiet;
static char *opt_field;

struct nvram {
	union {
		uint32_t words[3];
		uint8_t bytes[12];
		struct {
			uint32_t amiga;
			uint32_t amix;
			uint32_t shared;
		} bits;
	};
	uint8_t checksum;
} __attribute__ ((packed));

static struct nvram nvram, backup;

static const struct nvram_field {
	const char *name;
	unsigned int addr;
	unsigned int len;
} nvram_fields[] = {
	{ "amiga",			 0,	32 },
	{ "amiga.amnesia",		 0,	 1 },
	{ "amiga.scsi_timeout",		 1,	 1 },
	{ "amiga.scsi_luns",		 2,	 1 },
	{ "amix",			32,	32 },
	{ "shared",			64,	32 },
	{ "shared.amnesia",		64,	 1 },
	{ "shared.scsi_host_id",	65,	 3 },
	{ "shared.scsi_sync_xfer",	68,	 1 },
	{ "shared.scsi_fast_sync",	69,	 1 },
	{ "shared.scsi_tag_queues",	70,	 1 },
	{ "shared.ide_extra_wait_addr",	71,	 1 },
};


static void msg(const char *fmt, ...) __attribute__((format(printf, 1, 2)));
static void msg(const char *fmt, ...)
{
	va_list ap;

	if (!opt_quiet) {
		va_start(ap, fmt);
		vprintf(fmt, ap);
		va_end(ap);
	}
}

static int nvram_read(void)
{
	int file;
	ssize_t n;

	file = open(opt_nvram, O_RDONLY);
	if (file < 0) {
		perror("Cannot open NVRAM for reading");
		return -1;
	}

	n = read(file, &nvram, sizeof(nvram));
	if (n < 0) {
		perror("Cannot read NVRAM");
		goto failed;
	}
	if (n < sizeof(nvram.bytes)) {
		fprintf(stderr, "Could read only %zu NVRAM bytes\n", n);
		goto failed;
	}
	if (n < sizeof(nvram)) {
		fprintf(stderr,
			"Warning: Could not read checksum, assuming zero\n");
		nvram.checksum = 0;
	}

	close(file);

	memcpy(&backup, &nvram, sizeof(nvram));
	return 0;

failed:
	close(file);
	return -1;
}


static int nvram_write(void)
{
	int file;
	ssize_t n;

	if (!memcmp(&nvram, &backup, sizeof(nvram)))
		return 0;

	msg("Saving NVRAM\n");

	file = open(opt_nvram, O_WRONLY);
	if (file < 0) {
		perror("Cannot open NVRAM for writing");
		return -1;
	}

	n = write(file, &nvram, sizeof(nvram));
	if (n < 0) {
		perror("Cannot write NVRAM");
		goto failed;
	}
	if (n < sizeof(nvram)) {
		fprintf(stderr, "Could write only %zu NVRAM bytes\n", n);
		goto failed;
	}

	close(file);
	return 0;

failed:
	close(file);
	return -1;
}


static const uint8_t table[16] = {
	0x00, 0x57, 0xae, 0xf9, 0x0b, 0x5c, 0xa5, 0xf2,
	0x16, 0x41, 0xb8, 0x7f, 0x1d, 0x4a, 0xb3, 0xe4
};

static uint8_t checksum_nibble(uint8_t sum, uint8_t nibble)
{
	uint8_t index = (sum >> 4) ^ nibble;
	sum = (sum << 4) ^ table[index];
	return sum;
}

static uint8_t nvram_checksum(void)
{
	unsigned int i;
	uint8_t sum = 0xff;

	for (i = 0; i < sizeof(nvram.bytes); i++) {
		sum = checksum_nibble(sum, nvram.bytes[i] >> 4);
		sum = checksum_nibble(sum, nvram.bytes[i] & 0x0f);
	}
	return sum;
}


uint32_t be32_to_cpu(uint32_t x)
{
	uint8_t bytes[4];

	*(uint32_t *)bytes = x;
	return bytes[0] << 24 | bytes[1] << 16 | bytes[2] << 8 | bytes[3];
}

static uint32_t nvram_get_field(const struct nvram_field *field)
{
	unsigned int word = field->addr / 32;
	unsigned int offset = field->addr % 32;
	unsigned int len = field->len;
	uint32_t val = be32_to_cpu(nvram.words[word]);

	if (len == 32)
		return val;

	val >>= 32 - offset - len;
	val &= (1 << len) - 1;
	return val;
}

static void nvram_set_field(const struct nvram_field *field, uint32_t val)
{
	unsigned int word = field->addr / 32;
	unsigned int offset = field->addr % 32;
	unsigned int len = field->len;
	uint32_t mask, shift, t;

	if (len == 32) {
		nvram.words[word] = be32_to_cpu(val);
		return;
	}

	mask = (1 << len) - 1;
	val &= mask;
	shift = 32 - offset - len;
	val <<= shift;
	mask <<= shift;

	t = be32_to_cpu(nvram.words[word]);
	nvram.words[word] = be32_to_cpu((t & ~mask) | val);
}

static const struct nvram_field *nvram_find_field(const char *name)
{
	unsigned int i;

	for (i = 0; i < ARRAY_SIZE(nvram_fields); i++)
		if (!strcmp(nvram_fields[i].name, name))
			return &nvram_fields[i];

	return NULL;
}

static void nvram_dump(void)
{
	unsigned int i;
	unsigned int max_name_len = 0;
	uint8_t sum;

	for (i = 0; i < ARRAY_SIZE(nvram_fields); i++) {
		size_t len = strlen(nvram_fields[i].name);
		if (len > max_name_len)
			max_name_len = len;
	}

	for (i = 0; i < ARRAY_SIZE(nvram_fields); i++) {
		const struct nvram_field *field = &nvram_fields[i];
		uint32_t val = nvram_get_field(field);
		if (field->len == 32)
			printf("%-*s = 0x%08x\n", max_name_len, field->name,
			       val);
		else
			printf("%-*s = %u\n", max_name_len, field->name, val);
	}
	printf("%-*s = 0x%02x ", max_name_len, "checksum", nvram.checksum);
	sum = nvram_checksum();
	if (sum == nvram.checksum)
		puts("[correct]");
	else
		printf("[not correct, should be 0x%02x]\n", sum);
}


static void usage(void) __attribute__ ((noreturn));

static void usage(void)
{
	fprintf(stderr,
		"\n"
		"%s: [options] [<field>[=<value>]]\n\n"
		"Valid options are:\n"
		"    -c, --checksum   Recalculate checksum\n"
		"                     (auto-enabled when a field is modified)\n"
		"    -f, --file file  Specify NVRAM file\n"
		"                     (default: %s)\n"
		"    -h, --help       Display this usage information\n"
		"    -q, --quiet      Enable quiet mode\n"
		"\n",
		program_name, opt_nvram);
	exit(1);
}


int main(int argc, char *argv[])
{
	const char *slash = strrchr(argv[0], '/');
	program_name = slash ? slash + 1 : argv[0];
	int error;

	while (argc > 1) {
		if (!strcmp(argv[1], "-h") || !strcmp(argv[1], "--help"))
			usage();
		else if (!strcmp(argv[1], "-c") ||
			   !strcmp(argv[1], "--checksum")) {
			opt_checksum = 1;
			argv++;
			argc--;
		} else if (!strcmp(argv[1], "-f") ||
			 !strcmp(argv[1], "--file")) {
			if (argc <= 2)
				usage();
			opt_nvram = argv[2];
			argv += 2;
			argc -= 2;
		} else if (!strcmp(argv[1], "-q") ||
			   !strcmp(argv[1], "--quiet")) {
			opt_quiet = 1;
			argv++;
			argc--;
		} else if (!opt_field) {
			opt_field = argv[1];
			argv++;
			argc--;
		} else
			usage();
	}

	error = nvram_read();
	if (error)
		exit(-1);

	if (opt_field) {
		uint32_t val;
		char *equal = strchr(opt_field, '=');
		if (equal)
			*equal = '\0';

		const struct nvram_field *field = nvram_find_field(opt_field);
		if (!field) {
			fprintf(stderr, "Cannot find NVRAM field %s\n",
				opt_field);
			exit(-1);
		}

		if (!equal) {
			val = nvram_get_field(field);
			if (field->len == 32)
				printf("%s = 0x%08x\n", field->name, val);
			else
				printf("%s = %u\n", field->name, val);
		} else {
			val = strtoul(equal+1, NULL, 0);
			nvram_set_field(field, val);
			opt_checksum = 1;
		}
	} else if (!opt_quiet)
		nvram_dump();

	if (opt_checksum) {
		uint8_t sum = nvram_checksum();
		if (sum != nvram.checksum) {
			msg("Correcting checksum\n");
			nvram.checksum = sum;
		}
	}

	error = nvram_write();
	if (error)
		exit(-1);

	exit(0);
}