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devmem: map two pages only if it is necessary
function old new delta devmem_main 463 469 +6 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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@ -13,9 +13,9 @@ int devmem_main(int argc UNUSED_PARAM, char **argv)
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uint64_t read_result;
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uint64_t writeval = writeval; /* for compiler */
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off_t target;
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unsigned page_size = getpagesize();
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unsigned page_size, mapped_size, offset_in_page;
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int fd;
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int width = 8 * sizeof(int);
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unsigned width = 8 * sizeof(int);
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/* devmem ADDRESS [WIDTH [VALUE]] */
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// TODO: options?
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@ -50,15 +50,22 @@ int devmem_main(int argc UNUSED_PARAM, char **argv)
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if (argv[3])
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writeval = bb_strtoull(argv[3], NULL, 0);
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} else { /* argv[2] == NULL */
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/* make argv[3] to be a valid thing to use */
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/* make argv[3] to be a valid thing to fetch */
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argv--;
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}
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if (errno)
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bb_show_usage(); /* bb_strtouXX failed */
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bb_show_usage(); /* one of bb_strtouXX failed */
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fd = xopen("/dev/mem", argv[3] ? (O_RDWR | O_SYNC) : (O_RDONLY | O_SYNC));
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mapped_size = page_size = getpagesize();
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offset_in_page = (unsigned)target & (page_size - 1);
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if (offset_in_page + width > page_size) {
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/* This access spans pages.
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* Must map two pages to make it possible: */
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mapped_size *= 2;
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}
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map_base = mmap(NULL,
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page_size * 2 /* in case value spans page */,
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mapped_size,
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argv[3] ? (PROT_READ | PROT_WRITE) : PROT_READ,
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MAP_SHARED,
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fd,
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@ -68,7 +75,7 @@ int devmem_main(int argc UNUSED_PARAM, char **argv)
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// printf("Memory mapped at address %p.\n", map_base);
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virt_addr = (char*)map_base + (target & (page_size - 1));
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virt_addr = (char*)map_base + offset_in_page;
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if (!argv[3]) {
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switch (width) {
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@ -119,7 +126,7 @@ int devmem_main(int argc UNUSED_PARAM, char **argv)
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}
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if (ENABLE_FEATURE_CLEAN_UP) {
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if (munmap(map_base, page_size * 2) == -1)
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if (munmap(map_base, mapped_size) == -1)
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bb_perror_msg_and_die("munmap");
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close(fd);
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}
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