devmem: new applet
diff --git a/miscutils/devmem.c b/miscutils/devmem.c
new file mode 100644
index 0000000..8b8edbe
--- /dev/null
+++ b/miscutils/devmem.c
@@ -0,0 +1,123 @@
+/*
+ * 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;
+}