1 /* 2 * This file is part of the Linux kernel, and is made available under 3 * the terms of the GNU General Public License version 2. 4 * 5 * Misc librarized functions for cmdline poking. 6 */ 7 #include <linux/kernel.h> 8 #include <linux/string.h> 9 #include <linux/ctype.h> 10 #include <asm/setup.h> 11 12 static inline int myisspace(u8 c) 13 { 14 return c <= ' '; /* Close enough approximation */ 15 } 16 17 /** 18 * Find a boolean option (like quiet,noapic,nosmp....) 19 * 20 * @cmdline: the cmdline string 21 * @option: option string to look for 22 * 23 * Returns the position of that @option (starts counting with 1) 24 * or 0 on not found. 25 */ 26 int cmdline_find_option_bool(const char *cmdline, const char *option) 27 { 28 char c; 29 int len, pos = 0, wstart = 0; 30 const char *opptr = NULL; 31 enum { 32 st_wordstart = 0, /* Start of word/after whitespace */ 33 st_wordcmp, /* Comparing this word */ 34 st_wordskip, /* Miscompare, skip */ 35 } state = st_wordstart; 36 37 if (!cmdline) 38 return -1; /* No command line */ 39 40 len = min_t(int, strlen(cmdline), COMMAND_LINE_SIZE); 41 if (!len) 42 return 0; 43 44 while (len--) { 45 c = *(char *)cmdline++; 46 pos++; 47 48 switch (state) { 49 case st_wordstart: 50 if (!c) 51 return 0; 52 else if (myisspace(c)) 53 break; 54 55 state = st_wordcmp; 56 opptr = option; 57 wstart = pos; 58 /* fall through */ 59 60 case st_wordcmp: 61 if (!*opptr) 62 if (!c || myisspace(c)) 63 return wstart; 64 else 65 state = st_wordskip; 66 else if (!c) 67 return 0; 68 else if (c != *opptr++) 69 state = st_wordskip; 70 else if (!len) /* last word and is matching */ 71 return wstart; 72 break; 73 74 case st_wordskip: 75 if (!c) 76 return 0; 77 else if (myisspace(c)) 78 state = st_wordstart; 79 break; 80 } 81 } 82 83 return 0; /* Buffer overrun */ 84 } 85