File: /usr/src/linux/include/asm/bitops.h
1 #ifndef _I386_BITOPS_H
2 #define _I386_BITOPS_H
3
4 /*
5 * Copyright 1992, Linus Torvalds.
6 */
7
8 #include <linux/config.h>
9
10 /*
11 * These have to be done with inline assembly: that way the bit-setting
12 * is guaranteed to be atomic. All bit operations return 0 if the bit
13 * was cleared before the operation and != 0 if it was not.
14 *
15 * bit 0 is the LSB of addr; bit 32 is the LSB of (addr+1).
16 */
17
18 #ifdef CONFIG_SMP
19 #define LOCK_PREFIX "lock ; "
20 #else
21 #define LOCK_PREFIX ""
22 #endif
23
24 #define ADDR (*(volatile long *) addr)
25
26 /**
27 * set_bit - Atomically set a bit in memory
28 * @nr: the bit to set
29 * @addr: the address to start counting from
30 *
31 * This function is atomic and may not be reordered. See __set_bit()
32 * if you do not require the atomic guarantees.
33 * Note that @nr may be almost arbitrarily large; this function is not
34 * restricted to acting on a single-word quantity.
35 */
36 static __inline__ void set_bit(int nr, volatile void * addr)
37 {
38 __asm__ __volatile__( LOCK_PREFIX
39 "btsl %1,%0"
40 :"=m" (ADDR)
41 :"Ir" (nr));
42 }
43
44 /**
45 * __set_bit - Set a bit in memory
46 * @nr: the bit to set
47 * @addr: the address to start counting from
48 *
49 * Unlike set_bit(), this function is non-atomic and may be reordered.
50 * If it's called on the same region of memory simultaneously, the effect
51 * may be that only one operation succeeds.
52 */
53 static __inline__ void __set_bit(int nr, volatile void * addr)
54 {
55 __asm__(
56 "btsl %1,%0"
57 :"=m" (ADDR)
58 :"Ir" (nr));
59 }
60
61 /**
62 * clear_bit - Clears a bit in memory
63 * @nr: Bit to clear
64 * @addr: Address to start counting from
65 *
66 * clear_bit() is atomic and may not be reordered. However, it does
67 * not contain a memory barrier, so if it is used for locking purposes,
68 * you should call smp_mb__before_clear_bit() and/or smp_mb__after_clear_bit()
69 * in order to ensure changes are visible on other processors.
70 */
71 static __inline__ void clear_bit(int nr, volatile void * addr)
72 {
73 __asm__ __volatile__( LOCK_PREFIX
74 "btrl %1,%0"
75 :"=m" (ADDR)
76 :"Ir" (nr));
77 }
78 #define smp_mb__before_clear_bit() barrier()
79 #define smp_mb__after_clear_bit() barrier()
80
81 /**
82 * __change_bit - Toggle a bit in memory
83 * @nr: the bit to set
84 * @addr: the address to start counting from
85 *
86 * Unlike change_bit(), this function is non-atomic and may be reordered.
87 * If it's called on the same region of memory simultaneously, the effect
88 * may be that only one operation succeeds.
89 */
90 static __inline__ void __change_bit(int nr, volatile void * addr)
91 {
92 __asm__ __volatile__(
93 "btcl %1,%0"
94 :"=m" (ADDR)
95 :"Ir" (nr));
96 }
97
98 /**
99 * change_bit - Toggle a bit in memory
100 * @nr: Bit to clear
101 * @addr: Address to start counting from
102 *
103 * change_bit() is atomic and may not be reordered.
104 * Note that @nr may be almost arbitrarily large; this function is not
105 * restricted to acting on a single-word quantity.
106 */
107 static __inline__ void change_bit(int nr, volatile void * addr)
108 {
109 __asm__ __volatile__( LOCK_PREFIX
110 "btcl %1,%0"
111 :"=m" (ADDR)
112 :"Ir" (nr));
113 }
114
115 /**
116 * test_and_set_bit - Set a bit and return its old value
117 * @nr: Bit to set
118 * @addr: Address to count from
119 *
120 * This operation is atomic and cannot be reordered.
121 * It also implies a memory barrier.
122 */
123 static __inline__ int test_and_set_bit(int nr, volatile void * addr)
124 {
125 int oldbit;
126
127 __asm__ __volatile__( LOCK_PREFIX
128 "btsl %2,%1\n\tsbbl %0,%0"
129 :"=r" (oldbit),"=m" (ADDR)
130 :"Ir" (nr) : "memory");
131 return oldbit;
132 }
133
134 /**
135 * __test_and_set_bit - Set a bit and return its old value
136 * @nr: Bit to set
137 * @addr: Address to count from
138 *
139 * This operation is non-atomic and can be reordered.
140 * If two examples of this operation race, one can appear to succeed
141 * but actually fail. You must protect multiple accesses with a lock.
142 */
143 static __inline__ int __test_and_set_bit(int nr, volatile void * addr)
144 {
145 int oldbit;
146
147 __asm__(
148 "btsl %2,%1\n\tsbbl %0,%0"
149 :"=r" (oldbit),"=m" (ADDR)
150 :"Ir" (nr));
151 return oldbit;
152 }
153
154 /**
155 * test_and_clear_bit - Clear a bit and return its old value
156 * @nr: Bit to set
157 * @addr: Address to count from
158 *
159 * This operation is atomic and cannot be reordered.
160 * It also implies a memory barrier.
161 */
162 static __inline__ int test_and_clear_bit(int nr, volatile void * addr)
163 {
164 int oldbit;
165
166 __asm__ __volatile__( LOCK_PREFIX
167 "btrl %2,%1\n\tsbbl %0,%0"
168 :"=r" (oldbit),"=m" (ADDR)
169 :"Ir" (nr) : "memory");
170 return oldbit;
171 }
172
173 /**
174 * __test_and_clear_bit - Clear a bit and return its old value
175 * @nr: Bit to set
176 * @addr: Address to count from
177 *
178 * This operation is non-atomic and can be reordered.
179 * If two examples of this operation race, one can appear to succeed
180 * but actually fail. You must protect multiple accesses with a lock.
181 */
182 static __inline__ int __test_and_clear_bit(int nr, volatile void * addr)
183 {
184 int oldbit;
185
186 __asm__(
187 "btrl %2,%1\n\tsbbl %0,%0"
188 :"=r" (oldbit),"=m" (ADDR)
189 :"Ir" (nr));
190 return oldbit;
191 }
192
193 /* WARNING: non atomic and it can be reordered! */
194 static __inline__ int __test_and_change_bit(int nr, volatile void * addr)
195 {
196 int oldbit;
197
198 __asm__ __volatile__(
199 "btcl %2,%1\n\tsbbl %0,%0"
200 :"=r" (oldbit),"=m" (ADDR)
201 :"Ir" (nr) : "memory");
202 return oldbit;
203 }
204
205 /**
206 * test_and_change_bit - Change a bit and return its new value
207 * @nr: Bit to set
208 * @addr: Address to count from
209 *
210 * This operation is atomic and cannot be reordered.
211 * It also implies a memory barrier.
212 */
213 static __inline__ int test_and_change_bit(int nr, volatile void * addr)
214 {
215 int oldbit;
216
217 __asm__ __volatile__( LOCK_PREFIX
218 "btcl %2,%1\n\tsbbl %0,%0"
219 :"=r" (oldbit),"=m" (ADDR)
220 :"Ir" (nr) : "memory");
221 return oldbit;
222 }
223
224 #if 0 /* Fool kernel-doc since it doesn't do macros yet */
225 /**
226 * test_bit - Determine whether a bit is set
227 * @nr: bit number to test
228 * @addr: Address to start counting from
229 */
230 static int test_bit(int nr, const volatile void * addr);
231 #endif
232
233 static __inline__ int constant_test_bit(int nr, const volatile void * addr)
234 {
235 return ((1UL << (nr & 31)) & (((const volatile unsigned int *) addr)[nr >> 5])) != 0;
236 }
237
238 static __inline__ int variable_test_bit(int nr, volatile void * addr)
239 {
240 int oldbit;
241
242 __asm__ __volatile__(
243 "btl %2,%1\n\tsbbl %0,%0"
244 :"=r" (oldbit)
245 :"m" (ADDR),"Ir" (nr));
246 return oldbit;
247 }
248
249 #define test_bit(nr,addr) \
250 (__builtin_constant_p(nr) ? \
251 constant_test_bit((nr),(addr)) : \
252 variable_test_bit((nr),(addr)))
253
254 /**
255 * find_first_zero_bit - find the first zero bit in a memory region
256 * @addr: The address to start the search at
257 * @size: The maximum size to search
258 *
259 * Returns the bit-number of the first zero bit, not the number of the byte
260 * containing a bit.
261 */
262 static __inline__ int find_first_zero_bit(void * addr, unsigned size)
263 {
264 int d0, d1, d2;
265 int res;
266
267 if (!size)
268 return 0;
269 /* This looks at memory. Mark it volatile to tell gcc not to move it around */
270 __asm__ __volatile__(
271 "movl $-1,%%eax\n\t"
272 "xorl %%edx,%%edx\n\t"
273 "repe; scasl\n\t"
274 "je 1f\n\t"
275 "xorl -4(%%edi),%%eax\n\t"
276 "subl $4,%%edi\n\t"
277 "bsfl %%eax,%%edx\n"
278 "1:\tsubl %%ebx,%%edi\n\t"
279 "shll $3,%%edi\n\t"
280 "addl %%edi,%%edx"
281 :"=d" (res), "=&c" (d0), "=&D" (d1), "=&a" (d2)
282 :"1" ((size + 31) >> 5), "2" (addr), "b" (addr));
283 return res;
284 }
285
286 /**
287 * find_next_zero_bit - find the first zero bit in a memory region
288 * @addr: The address to base the search on
289 * @offset: The bitnumber to start searching at
290 * @size: The maximum size to search
291 */
292 static __inline__ int find_next_zero_bit (void * addr, int size, int offset)
293 {
294 unsigned long * p = ((unsigned long *) addr) + (offset >> 5);
295 int set = 0, bit = offset & 31, res;
296
297 if (bit) {
298 /*
299 * Look for zero in first byte
300 */
301 __asm__("bsfl %1,%0\n\t"
302 "jne 1f\n\t"
303 "movl $32, %0\n"
304 "1:"
305 : "=r" (set)
306 : "r" (~(*p >> bit)));
307 if (set < (32 - bit))
308 return set + offset;
309 set = 32 - bit;
310 p++;
311 }
312 /*
313 * No zero yet, search remaining full bytes for a zero
314 */
315 res = find_first_zero_bit (p, size - 32 * (p - (unsigned long *) addr));
316 return (offset + set + res);
317 }
318
319 /**
320 * ffz - find first zero in word.
321 * @word: The word to search
322 *
323 * Undefined if no zero exists, so code should check against ~0UL first.
324 */
325 static __inline__ unsigned long ffz(unsigned long word)
326 {
327 __asm__("bsfl %1,%0"
328 :"=r" (word)
329 :"r" (~word));
330 return word;
331 }
332
333 #ifdef __KERNEL__
334
335 /**
336 * ffs - find first bit set
337 * @x: the word to search
338 *
339 * This is defined the same way as
340 * the libc and compiler builtin ffs routines, therefore
341 * differs in spirit from the above ffz (man ffs).
342 */
343 static __inline__ int ffs(int x)
344 {
345 int r;
346
347 __asm__("bsfl %1,%0\n\t"
348 "jnz 1f\n\t"
349 "movl $-1,%0\n"
350 "1:" : "=r" (r) : "g" (x));
351 return r+1;
352 }
353
354 /**
355 * hweightN - returns the hamming weight of a N-bit word
356 * @x: the word to weigh
357 *
358 * The Hamming Weight of a number is the total number of bits set in it.
359 */
360
361 #define hweight32(x) generic_hweight32(x)
362 #define hweight16(x) generic_hweight16(x)
363 #define hweight8(x) generic_hweight8(x)
364
365 #endif /* __KERNEL__ */
366
367 #ifdef __KERNEL__
368
369 #define ext2_set_bit __test_and_set_bit
370 #define ext2_clear_bit __test_and_clear_bit
371 #define ext2_test_bit test_bit
372 #define ext2_find_first_zero_bit find_first_zero_bit
373 #define ext2_find_next_zero_bit find_next_zero_bit
374
375 /* Bitmap functions for the minix filesystem. */
376 #define minix_test_and_set_bit(nr,addr) __test_and_set_bit(nr,addr)
377 #define minix_set_bit(nr,addr) __set_bit(nr,addr)
378 #define minix_test_and_clear_bit(nr,addr) __test_and_clear_bit(nr,addr)
379 #define minix_test_bit(nr,addr) test_bit(nr,addr)
380 #define minix_find_first_zero_bit(addr,size) find_first_zero_bit(addr,size)
381
382 #endif /* __KERNEL__ */
383
384 #endif /* _I386_BITOPS_H */
385