043246560
Denis Vlasenko
2008-10-26
Subject
devmem: make it more script-friendly; don't do any reads and output nothing if writing was requested. -100 bytes
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Commit Diff GitHub →
miscutils/devmem.c+42 -37
| @@ -6,9 +6,6 @@ | |
| #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) | |
| { | |
| @@ -16,10 +13,16 @@ int devmem_main(int argc UNUSED_PARAM, char **argv) | |
| uint64_t read_result; | |
| uint64_t writeval = writeval; /* for compiler */ | |
| off_t target; | |
| + | unsigned page_size = getpagesize(); |
| int fd; | |
| int width = 8 * sizeof(int); | |
| /* devmem ADDRESS [WIDTH [VALUE]] */ | |
| + | // TODO: options? |
| + | // -r: read and output only the value in hex, with 0x prefix |
| + | // -w: write only, no reads before or after, and no output |
| + | // or make this behavior default? |
| + | // Let's try this and see how users react. |
| /* ADDRESS */ | |
| if (!argv[1]) | |
| @@ -54,67 +57,69 @@ int devmem_main(int argc UNUSED_PARAM, char **argv) | |
| 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 */, |
| + | page_size * 2 /* in case value spans page */, |
| argv[3] ? (PROT_READ | PROT_WRITE) : PROT_READ, | |
| MAP_SHARED, | |
| fd, | |
| - | target & ~DEVMEM_MAP_MASK); |
| + | target & ~(off_t)(page_size - 1)); |
| 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); |
| + | virt_addr = (char*)map_base + (target & (page_size - 1)); |
| - | if (argv[3]) { |
| + | 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; | |
| + | 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); |
| + | /* Zero-padded output shows the width of access just done */ |
| + | printf("0x%0*llX\n", (width >> 2), (unsigned long long)read_result); |
| + | } else { |
| + | 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; |
| + | default: |
| + | bb_error_msg_and_die("bad width"); |
| } | |
| - | printf("Written 0x%llX; readback 0x%llX\n", |
| - | (unsigned long long)writeval, |
| - | (unsigned long long)read_result); |
| + | // 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) |
| + | if (munmap(map_base, page_size) == -1) |
| bb_perror_msg_and_die("munmap"); | |
| close(fd); | |
| } | |