linux/include/linux/genalloc.h
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   1/*
   2 * Basic general purpose allocator for managing special purpose
   3 * memory, for example, memory that is not managed by the regular
   4 * kmalloc/kfree interface.  Uses for this includes on-device special
   5 * memory, uncached memory etc.
   6 *
   7 * It is safe to use the allocator in NMI handlers and other special
   8 * unblockable contexts that could otherwise deadlock on locks.  This
   9 * is implemented by using atomic operations and retries on any
  10 * conflicts.  The disadvantage is that there may be livelocks in
  11 * extreme cases.  For better scalability, one allocator can be used
  12 * for each CPU.
  13 *
  14 * The lockless operation only works if there is enough memory
  15 * available.  If new memory is added to the pool a lock has to be
  16 * still taken.  So any user relying on locklessness has to ensure
  17 * that sufficient memory is preallocated.
  18 *
  19 * The basic atomic operation of this allocator is cmpxchg on long.
  20 * On architectures that don't have NMI-safe cmpxchg implementation,
  21 * the allocator can NOT be used in NMI handler.  So code uses the
  22 * allocator in NMI handler should depend on
  23 * CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
  24 *
  25 * This source code is licensed under the GNU General Public License,
  26 * Version 2.  See the file COPYING for more details.
  27 */
  28
  29
  30#ifndef __GENALLOC_H__
  31#define __GENALLOC_H__
  32/*
  33 *  General purpose special memory pool descriptor.
  34 */
  35struct gen_pool {
  36        spinlock_t lock;
  37        struct list_head chunks;        /* list of chunks in this pool */
  38        int min_alloc_order;            /* minimum allocation order */
  39};
  40
  41/*
  42 *  General purpose special memory pool chunk descriptor.
  43 */
  44struct gen_pool_chunk {
  45        struct list_head next_chunk;    /* next chunk in pool */
  46        atomic_t avail;
  47        phys_addr_t phys_addr;          /* physical starting address of memory chunk */
  48        unsigned long start_addr;       /* starting address of memory chunk */
  49        unsigned long end_addr;         /* ending address of memory chunk */
  50        unsigned long bits[0];          /* bitmap for allocating memory chunk */
  51};
  52
  53extern struct gen_pool *gen_pool_create(int, int);
  54extern phys_addr_t gen_pool_virt_to_phys(struct gen_pool *pool, unsigned long);
  55extern int gen_pool_add_virt(struct gen_pool *, unsigned long, phys_addr_t,
  56                             size_t, int);
  57/**
  58 * gen_pool_add - add a new chunk of special memory to the pool
  59 * @pool: pool to add new memory chunk to
  60 * @addr: starting address of memory chunk to add to pool
  61 * @size: size in bytes of the memory chunk to add to pool
  62 * @nid: node id of the node the chunk structure and bitmap should be
  63 *       allocated on, or -1
  64 *
  65 * Add a new chunk of special memory to the specified pool.
  66 *
  67 * Returns 0 on success or a -ve errno on failure.
  68 */
  69static inline int gen_pool_add(struct gen_pool *pool, unsigned long addr,
  70                               size_t size, int nid)
  71{
  72        return gen_pool_add_virt(pool, addr, -1, size, nid);
  73}
  74extern void gen_pool_destroy(struct gen_pool *);
  75extern unsigned long gen_pool_alloc(struct gen_pool *, size_t);
  76extern void gen_pool_free(struct gen_pool *, unsigned long, size_t);
  77extern void gen_pool_for_each_chunk(struct gen_pool *,
  78        void (*)(struct gen_pool *, struct gen_pool_chunk *, void *), void *);
  79extern size_t gen_pool_avail(struct gen_pool *);
  80extern size_t gen_pool_size(struct gen_pool *);
  81#endif /* __GENALLOC_H__ */
  82
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