/*
 * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
 *  Copyright (C) 2000, Jan-Derk Bakker (J.D.Bakker@its.tudelft.nl)
 *  Copyright (C) 2008, BusyBox Team. -solar 4/26/08
 */

#include "libbb.h"

#define DEVMEM_MAP_SIZE 4096
#define DEVMEM_MAP_MASK (off_t)(DEVMEM_MAP_SIZE - 1)

int devmem_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int devmem_main(int argc UNUSED_PARAM, char **argv)
{
	void *map_base, *virt_addr;
	uint64_t read_result;
	uint64_t writeval = writeval; /* for compiler */
	off_t target;
	int fd;
	int width = 8 * sizeof(int);

	/* devmem ADDRESS [WIDTH [VALUE]] */

	/* ADDRESS */
	if (!argv[1])
		bb_show_usage();
	errno = 0;
	target = bb_strtoull(argv[1], NULL, 0); /* allows hex, oct etc */

	/* WIDTH */
	if (argv[2]) {
		if (isdigit(argv[2][0]) || argv[2][1])
			width = xatou(argv[2]);
		else {
			static const char bhwl[] ALIGN1 = "bhwl";
			static const uint8_t sizes[] ALIGN1 = {
				8 * sizeof(char),
				8 * sizeof(short),
				8 * sizeof(int),
				8 * sizeof(long),
				0 /* bad */
			};
			width = strchrnul(bhwl, (argv[2][0] | 0x20)) - bhwl;
			width = sizes[width];
		}
		/* VALUE */
		if (argv[3])
			writeval = bb_strtoull(argv[3], NULL, 0);
	} else { /* argv[2] == NULL */
		/* make argv[3] to be a valid thing to use */
		argv--;
	}
	if (errno)
		bb_show_usage(); /* bb_strtouXX failed */

	fd = xopen("/dev/mem", argv[3] ? (O_RDWR | O_SYNC) : (O_RDONLY | O_SYNC));

	map_base = mmap(NULL,
			DEVMEM_MAP_SIZE * 2 /* in case value spans page */,
			argv[3] ? (PROT_READ | PROT_WRITE) : PROT_READ,
			MAP_SHARED,
			fd,
			target & ~DEVMEM_MAP_MASK);
	if (map_base == MAP_FAILED)
		bb_perror_msg_and_die("mmap");

//	printf("Memory mapped at address %p.\n", map_base);

	virt_addr = (char*)map_base + (target & DEVMEM_MAP_MASK);

	switch (width) {
	case 8:
		read_result = *(volatile uint8_t*)virt_addr;
		break;
	case 16:
		read_result = *(volatile uint16_t*)virt_addr;
		break;
	case 32:
		read_result = *(volatile uint32_t*)virt_addr;
		break;
	case 64:
		read_result = *(volatile uint64_t*)virt_addr;
		break;
	default:
		bb_error_msg_and_die("bad width");
	}

	printf("Value at address 0x%"OFF_FMT"X (%p): 0x%llX\n",
			target, virt_addr,
			(unsigned long long)read_result);

	if (argv[3]) {
		switch (width) {
		case 8:
			*(volatile uint8_t*)virt_addr = writeval;
			read_result = *(volatile uint8_t*)virt_addr;
			break;
		case 16:
			*(volatile uint16_t*)virt_addr = writeval;
			read_result = *(volatile uint16_t*)virt_addr;
			break;
		case 32:
			*(volatile uint32_t*)virt_addr = writeval;
			read_result = *(volatile uint32_t*)virt_addr;
			break;
		case 64:
			*(volatile uint64_t*)virt_addr = writeval;
			read_result = *(volatile uint64_t*)virt_addr;
			break;
		}
		printf("Written 0x%llX; readback 0x%llX\n",
				(unsigned long long)writeval,
				(unsigned long long)read_result);
	}

	if (ENABLE_FEATURE_CLEAN_UP) {
		if (munmap(map_base, DEVMEM_MAP_SIZE) == -1)
			bb_perror_msg_and_die("munmap");
		close(fd);
	}

	return EXIT_SUCCESS;
}