linux/drivers/android/dbitmap.h

/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * Copyright 2024 Google LLC
 *
 * dbitmap - dynamically sized bitmap library.
 *
 * Used by the binder driver to optimize the allocation of the smallest
 * available descriptor ID. Each bit in the bitmap represents the state
 * of an ID, with the exception of BIT(0) which is used exclusively to
 * reference binder's context manager.
 *
 * A dbitmap can grow or shrink as needed. This part has been designed
 * considering that users might need to briefly release their locks in
 * order to allocate memory for the new bitmap. These operations then,
 * are verified to determine if the grow or shrink is sill valid.
 *
 * This library does not provide protection against concurrent access
 * by itself. Binder uses the proc->outer_lock for this purpose.
 */

#ifndef _LINUX_DBITMAP_H
#define _LINUX_DBITMAP_H
#include <linux/bitmap.h>

#define NBITS_MIN …

struct dbitmap { … };

static inline int dbitmap_enabled(struct dbitmap *dmap)
{ … }

static inline void dbitmap_free(struct dbitmap *dmap)
{ … }

/* Returns the nbits that a dbitmap can shrink to, 0 if not possible. */
static inline unsigned int dbitmap_shrink_nbits(struct dbitmap *dmap)
{ … }

/* Replace the internal bitmap with a new one of different size */
static inline void
dbitmap_replace(struct dbitmap *dmap, unsigned long *new, unsigned int nbits)
{ … }

static inline void
dbitmap_shrink(struct dbitmap *dmap, unsigned long *new, unsigned int nbits)
{ … }

/* Returns the nbits that a dbitmap can grow to. */
static inline unsigned int dbitmap_grow_nbits(struct dbitmap *dmap)
{ … }

static inline void
dbitmap_grow(struct dbitmap *dmap, unsigned long *new, unsigned int nbits)
{ … }

/*
 * Finds and sets the first zero bit in the bitmap. Upon success @bit
 * is populated with the index and 0 is returned. Otherwise, -ENOSPC
 * is returned to indicate that a dbitmap_grow() is needed.
 */
static inline int
dbitmap_acquire_first_zero_bit(struct dbitmap *dmap, unsigned long *bit)
{ … }

static inline void
dbitmap_clear_bit(struct dbitmap *dmap, unsigned long bit)
{ … }

static inline int dbitmap_init(struct dbitmap *dmap)
{ … }
#endif