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drm_mm.c

/**************************************************************************
 *
 * Copyright 2006 Tungsten Graphics, Inc., Bismarck, ND., USA.
 * All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sub license, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice (including the
 * next paragraph) shall be included in all copies or substantial portions
 * of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
 * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 * USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 *
 **************************************************************************/

/*
 * Generic simple memory manager implementation. Intended to be used as a base
 * class implementation for more advanced memory managers.
 *
 * Note that the algorithm used is quite simple and there might be substantial
 * performance gains if a smarter free list is implemented. Currently it is just an
 * unordered stack of free regions. This could easily be improved if an RB-tree
 * is used instead. At least if we expect heavy fragmentation.
 *
 * Aligned allocations can also see improvement.
 *
 * Authors:
 * Thomas Hellström <thomas-at-tungstengraphics-dot-com>
 */

#include "drmP.h"
#include <linux/slab.h>

unsigned long drm_mm_tail_space(struct drm_mm *mm)
{
      struct list_head *tail_node;
      struct drm_mm_node *entry;

      tail_node = mm->ml_entry.prev;
      entry = list_entry(tail_node, struct drm_mm_node, ml_entry);
      if (!entry->free)
            return 0;

      return entry->size;
}

int drm_mm_remove_space_from_tail(struct drm_mm *mm, unsigned long size)
{
      struct list_head *tail_node;
      struct drm_mm_node *entry;

      tail_node = mm->ml_entry.prev;
      entry = list_entry(tail_node, struct drm_mm_node, ml_entry);
      if (!entry->free)
            return -ENOMEM;

      if (entry->size <= size)
            return -ENOMEM;

      entry->size -= size;
      return 0;
}


static int drm_mm_create_tail_node(struct drm_mm *mm,
                      unsigned long start,
                      unsigned long size)
{
      struct drm_mm_node *child;

      child = (struct drm_mm_node *)
            drm_alloc(sizeof(*child), DRM_MEM_MM);
      if (!child)
            return -ENOMEM;

      child->free = 1;
      child->size = size;
      child->start = start;
      child->mm = mm;

      list_add_tail(&child->ml_entry, &mm->ml_entry);
      list_add_tail(&child->fl_entry, &mm->fl_entry);

      return 0;
}


int drm_mm_add_space_to_tail(struct drm_mm *mm, unsigned long size)
{
      struct list_head *tail_node;
      struct drm_mm_node *entry;

      tail_node = mm->ml_entry.prev;
      entry = list_entry(tail_node, struct drm_mm_node, ml_entry);
      if (!entry->free) {
            return drm_mm_create_tail_node(mm, entry->start + entry->size, size);
      }
      entry->size += size;
      return 0;
}

static struct drm_mm_node *drm_mm_split_at_start(struct drm_mm_node *parent,
                                  unsigned long size)
{
      struct drm_mm_node *child;

      child = (struct drm_mm_node *)
            drm_alloc(sizeof(*child), DRM_MEM_MM);
      if (!child)
            return NULL;

      INIT_LIST_HEAD(&child->fl_entry);

      child->free = 0;
      child->size = size;
      child->start = parent->start;
      child->mm = parent->mm;

      list_add_tail(&child->ml_entry, &parent->ml_entry);
      INIT_LIST_HEAD(&child->fl_entry);

      parent->size -= size;
      parent->start += size;
      return child;
}



struct drm_mm_node *drm_mm_get_block(struct drm_mm_node * parent,
                        unsigned long size, unsigned alignment)
{

      struct drm_mm_node *align_splitoff = NULL;
      struct drm_mm_node *child;
      unsigned tmp = 0;

      if (alignment)
            tmp = parent->start % alignment;

      if (tmp) {
            align_splitoff = drm_mm_split_at_start(parent, alignment - tmp);
            if (!align_splitoff)
                  return NULL;
      }

      if (parent->size == size) {
            list_del_init(&parent->fl_entry);
            parent->free = 0;
            return parent;
      } else {
            child = drm_mm_split_at_start(parent, size);
      }

      if (align_splitoff)
            drm_mm_put_block(align_splitoff);

      return child;
}

/*
 * Put a block. Merge with the previous and / or next block if they are free.
 * Otherwise add to the free stack.
 */

void drm_mm_put_block(struct drm_mm_node * cur)
{

      struct drm_mm *mm = cur->mm;
      struct list_head *cur_head = &cur->ml_entry;
      struct list_head *root_head = &mm->ml_entry;
      struct drm_mm_node *prev_node = NULL;
      struct drm_mm_node *next_node;

      int merged = 0;

      if (cur_head->prev != root_head) {
            prev_node = list_entry(cur_head->prev, struct drm_mm_node, ml_entry);
            if (prev_node->free) {
                  prev_node->size += cur->size;
                  merged = 1;
            }
      }
      if (cur_head->next != root_head) {
            next_node = list_entry(cur_head->next, struct drm_mm_node, ml_entry);
            if (next_node->free) {
                  if (merged) {
                        prev_node->size += next_node->size;
                        list_del(&next_node->ml_entry);
                        list_del(&next_node->fl_entry);
                        drm_free(next_node, sizeof(*next_node),
                               DRM_MEM_MM);
                  } else {
                        next_node->size += cur->size;
                        next_node->start = cur->start;
                        merged = 1;
                  }
            }
      }
      if (!merged) {
            cur->free = 1;
            list_add(&cur->fl_entry, &mm->fl_entry);
      } else {
            list_del(&cur->ml_entry);
            drm_free(cur, sizeof(*cur), DRM_MEM_MM);
      }
}

struct drm_mm_node *drm_mm_search_free(const struct drm_mm * mm,
                          unsigned long size,
                          unsigned alignment, int best_match)
{
      struct list_head *list;
      const struct list_head *free_stack = &mm->fl_entry;
      struct drm_mm_node *entry;
      struct drm_mm_node *best;
      unsigned long best_size;
      unsigned wasted;

      best = NULL;
      best_size = ~0UL;

      list_for_each(list, free_stack) {
            entry = list_entry(list, struct drm_mm_node, fl_entry);
            wasted = 0;

            if (entry->size < size)
                  continue;

            if (alignment) {
                  register unsigned tmp = entry->start % alignment;
                  if (tmp)
                        wasted += alignment - tmp;
            }


            if (entry->size >= size + wasted) {
                  if (!best_match)
                        return entry;
                  if (size < best_size) {
                        best = entry;
                        best_size = entry->size;
                  }
            }
      }

      return best;
}

int drm_mm_clean(struct drm_mm * mm)
{
      struct list_head *head = &mm->ml_entry;

      return (head->next->next == head);
}

int drm_mm_init(struct drm_mm * mm, unsigned long start, unsigned long size)
{
      INIT_LIST_HEAD(&mm->ml_entry);
      INIT_LIST_HEAD(&mm->fl_entry);

      return drm_mm_create_tail_node(mm, start, size);
}


void drm_mm_takedown(struct drm_mm * mm)
{
      struct list_head *bnode = mm->fl_entry.next;
      struct drm_mm_node *entry;

      entry = list_entry(bnode, struct drm_mm_node, fl_entry);

      if (entry->ml_entry.next != &mm->ml_entry ||
          entry->fl_entry.next != &mm->fl_entry) {
            DRM_ERROR("Memory manager not clean. Delaying takedown\n");
            return;
      }

      list_del(&entry->fl_entry);
      list_del(&entry->ml_entry);

      drm_free(entry, sizeof(*entry), DRM_MEM_MM);
}


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