include/linux/genalloc.h

   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  */
  35 struct 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  */
  44 struct 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
  53 extern struct gen_pool *gen_pool_create(int, int);
  54 extern phys_addr_t gen_pool_virt_to_phys(struct gen_pool *pool, unsigned long);
  55 extern 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  */
  69 static 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 }
  74 extern void gen_pool_destroy(struct gen_pool *);
  75 extern unsigned long gen_pool_alloc(struct gen_pool *, size_t);
  76 extern void gen_pool_free(struct gen_pool *, unsigned long, size_t);
  77 extern void gen_pool_for_each_chunk(struct gen_pool *,
  78         void (*)(struct gen_pool *, struct gen_pool_chunk *, void *), void *);
  79 extern size_t gen_pool_avail(struct gen_pool *);
  80 extern size_t gen_pool_size(struct gen_pool *);
  81 #endif /* __GENALLOC_H__ */