text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
   *                   Takashi Iwai <tiwai@suse.de>
   * 
   *  Generic memory allocators
   */
  
  #include <linux/slab.h>
  #include <linux/mm.h>
  #include <linux/dma-mapping.h>
  #include <linux/genalloc.h>
  #include <linux/highmem.h>
  #include <linux/vmalloc.h>
  #ifdef CONFIG_X86
  #include <asm/set_memory.h>
  #endif
  #include <sound/memalloc.h>
  #include "memalloc_local.h"
  
  static const struct snd_malloc_ops *snd_dma_get_ops(struct snd_dma_buffer *dmab);
  
  /* a cast to gfp flag from the dev pointer; for CONTINUOUS and VMALLOC types */
  static inline gfp_t snd_mem_get_gfp_flags(const struct snd_dma_buffer *dmab,
  					  gfp_t default_gfp)
  {
  	if (!dmab->dev.dev)
  		return default_gfp;
  	else
  		return (__force gfp_t)(unsigned long)dmab->dev.dev;
  }
  
  static void *__snd_dma_alloc_pages(struct snd_dma_buffer *dmab, size_t size)
  {
  	const struct snd_malloc_ops *ops = snd_dma_get_ops(dmab);
  
  	if (WARN_ON_ONCE(!ops || !ops->alloc))
  		return NULL;
  	return ops->alloc(dmab, size);
  }
  
  /**
   * snd_dma_alloc_dir_pages - allocate the buffer area according to the given
   *	type and direction
   * @type: the DMA buffer type
   * @device: the device pointer
   * @dir: DMA direction
   * @size: the buffer size to allocate
   * @dmab: buffer allocation record to store the allocated data
   *
   * Calls the memory-allocator function for the corresponding
   * buffer type.
   *
   * Return: Zero if the buffer with the given size is allocated successfully,
   * otherwise a negative value on error.
   */
  int snd_dma_alloc_dir_pages(int type, struct device *device,
  			    enum dma_data_direction dir, size_t size,
  			    struct snd_dma_buffer *dmab)
  {
  	if (WARN_ON(!size))
  		return -ENXIO;
  	if (WARN_ON(!dmab))
  		return -ENXIO;
  
  	size = PAGE_ALIGN(size);
  	dmab->dev.type = type;
  	dmab->dev.dev = device;
  	dmab->dev.dir = dir;
  	dmab->bytes = 0;
  	dmab->addr = 0;
  	dmab->private_data = NULL;
  	dmab->area = __snd_dma_alloc_pages(dmab, size);
  	if (!dmab->area)
  		return -ENOMEM;
  	dmab->bytes = size;
  	return 0;
  }
  EXPORT_SYMBOL(snd_dma_alloc_dir_pages);
  
  /**
   * snd_dma_alloc_pages_fallback - allocate the buffer area according to the given type with fallback
   * @type: the DMA buffer type
   * @device: the device pointer
   * @size: the buffer size to allocate
   * @dmab: buffer allocation record to store the allocated data
   *
   * Calls the memory-allocator function for the corresponding
   * buffer type.  When no space is left, this function reduces the size and
   * tries to allocate again.  The size actually allocated is stored in
   * res_size argument.
   *
   * Return: Zero if the buffer with the given size is allocated successfully,
   * otherwise a negative value on error.
   */
  int snd_dma_alloc_pages_fallback(int type, struct device *device, size_t size,
  				 struct snd_dma_buffer *dmab)
  {
  	int err;
  
  	while ((err = snd_dma_alloc_pages(type, device, size, dmab)) < 0) {
  		if (err != -ENOMEM)
  			return err;
  		if (size <= PAGE_SIZE)
  			return -ENOMEM;
  		size >>= 1;
  		size = PAGE_SIZE << get_order(size);
  	}
  	if (! dmab->area)
  		return -ENOMEM;
  	return 0;
  }
  EXPORT_SYMBOL(snd_dma_alloc_pages_fallback);
  
  /**
   * snd_dma_free_pages - release the allocated buffer
   * @dmab: the buffer allocation record to release
   *
   * Releases the allocated buffer via snd_dma_alloc_pages().
   */
  void snd_dma_free_pages(struct snd_dma_buffer *dmab)
  {
  	const struct snd_malloc_ops *ops = snd_dma_get_ops(dmab);
  
  	if (ops && ops->free)
  		ops->free(dmab);
  }
  EXPORT_SYMBOL(snd_dma_free_pages);
  
  /* called by devres */
  static void __snd_release_pages(struct device *dev, void *res)
  {
  	snd_dma_free_pages(res);
  }
  
  /**
   * snd_devm_alloc_dir_pages - allocate the buffer and manage with devres
   * @dev: the device pointer
   * @type: the DMA buffer type
   * @dir: DMA direction
   * @size: the buffer size to allocate
   *
   * Allocate buffer pages depending on the given type and manage using devres.
   * The pages will be released automatically at the device removal.
   *
   * Unlike snd_dma_alloc_pages(), this function requires the real device pointer,
   * hence it can't work with SNDRV_DMA_TYPE_CONTINUOUS or
   * SNDRV_DMA_TYPE_VMALLOC type.
   *
   * The function returns the snd_dma_buffer object at success, or NULL if failed.
   */
  struct snd_dma_buffer *
  snd_devm_alloc_dir_pages(struct device *dev, int type,
  			 enum dma_data_direction dir, size_t size)
  {
  	struct snd_dma_buffer *dmab;
  	int err;
  
  	if (WARN_ON(type == SNDRV_DMA_TYPE_CONTINUOUS ||
  		    type == SNDRV_DMA_TYPE_VMALLOC))
  		return NULL;
  
  	dmab = devres_alloc(__snd_release_pages, sizeof(*dmab), GFP_KERNEL);
  	if (!dmab)
  		return NULL;
  
  	err = snd_dma_alloc_dir_pages(type, dev, dir, size, dmab);
  	if (err < 0) {
  		devres_free(dmab);
  		return NULL;
  	}
  
  	devres_add(dev, dmab);
  	return dmab;
  }
  EXPORT_SYMBOL_GPL(snd_devm_alloc_dir_pages);
  
  /**
   * snd_dma_buffer_mmap - perform mmap of the given DMA buffer
   * @dmab: buffer allocation information
   * @area: VM area information
   */
  int snd_dma_buffer_mmap(struct snd_dma_buffer *dmab,
  			struct vm_area_struct *area)
  {
  	const struct snd_malloc_ops *ops;
  
  	if (!dmab)
  		return -ENOENT;
  	ops = snd_dma_get_ops(dmab);
  	if (ops && ops->mmap)
  		return ops->mmap(dmab, area);
  	else
  		return -ENOENT;
  }
  EXPORT_SYMBOL(snd_dma_buffer_mmap);
  
  #ifdef CONFIG_HAS_DMA
  /**
   * snd_dma_buffer_sync - sync DMA buffer between CPU and device
   * @dmab: buffer allocation information
   * @mode: sync mode
   */
  void snd_dma_buffer_sync(struct snd_dma_buffer *dmab,
  			 enum snd_dma_sync_mode mode)
  {
  	const struct snd_malloc_ops *ops;
  
  	if (!dmab || !dmab->dev.need_sync)
  		return;
  	ops = snd_dma_get_ops(dmab);
  	if (ops && ops->sync)
  		ops->sync(dmab, mode);
  }
  EXPORT_SYMBOL_GPL(snd_dma_buffer_sync);
  #endif /* CONFIG_HAS_DMA */
  
  /**
   * snd_sgbuf_get_addr - return the physical address at the corresponding offset
   * @dmab: buffer allocation information
   * @offset: offset in the ring buffer
   */
  dma_addr_t snd_sgbuf_get_addr(struct snd_dma_buffer *dmab, size_t offset)
  {
  	const struct snd_malloc_ops *ops = snd_dma_get_ops(dmab);
  
  	if (ops && ops->get_addr)
  		return ops->get_addr(dmab, offset);
  	else
  		return dmab->addr + offset;
  }
  EXPORT_SYMBOL(snd_sgbuf_get_addr);
  
  /**
   * snd_sgbuf_get_page - return the physical page at the corresponding offset
   * @dmab: buffer allocation information
   * @offset: offset in the ring buffer
   */
  struct page *snd_sgbuf_get_page(struct snd_dma_buffer *dmab, size_t offset)
  {
  	const struct snd_malloc_ops *ops = snd_dma_get_ops(dmab);
  
  	if (ops && ops->get_page)
  		return ops->get_page(dmab, offset);
  	else
  		return virt_to_page(dmab->area + offset);
  }
  EXPORT_SYMBOL(snd_sgbuf_get_page);
  
  /**
   * snd_sgbuf_get_chunk_size - compute the max chunk size with continuous pages
   *	on sg-buffer
   * @dmab: buffer allocation information
   * @ofs: offset in the ring buffer
   * @size: the requested size
   */
  unsigned int snd_sgbuf_get_chunk_size(struct snd_dma_buffer *dmab,
  				      unsigned int ofs, unsigned int size)
  {
  	const struct snd_malloc_ops *ops = snd_dma_get_ops(dmab);
  
  	if (ops && ops->get_chunk_size)
  		return ops->get_chunk_size(dmab, ofs, size);
  	else
  		return size;
  }
  EXPORT_SYMBOL(snd_sgbuf_get_chunk_size);
  
  /*
   * Continuous pages allocator
   */
  static void *snd_dma_continuous_alloc(struct snd_dma_buffer *dmab, size_t size)
  {
  	gfp_t gfp = snd_mem_get_gfp_flags(dmab, GFP_KERNEL);
  	void *p = alloc_pages_exact(size, gfp);
  
  	if (p)
  		dmab->addr = page_to_phys(virt_to_page(p));
  	return p;
  }
  
  static void snd_dma_continuous_free(struct snd_dma_buffer *dmab)
  {
  	free_pages_exact(dmab->area, dmab->bytes);
  }
  
  static int snd_dma_continuous_mmap(struct snd_dma_buffer *dmab,
  				   struct vm_area_struct *area)
  {
  	return remap_pfn_range(area, area->vm_start,
  			       dmab->addr >> PAGE_SHIFT,
  			       area->vm_end - area->vm_start,
  			       area->vm_page_prot);
  }
  
  static const struct snd_malloc_ops snd_dma_continuous_ops = {
  	.alloc = snd_dma_continuous_alloc,
  	.free = snd_dma_continuous_free,
  	.mmap = snd_dma_continuous_mmap,
  };
  
  /*
   * VMALLOC allocator
   */
  static void *snd_dma_vmalloc_alloc(struct snd_dma_buffer *dmab, size_t size)
  {
  	gfp_t gfp = snd_mem_get_gfp_flags(dmab, GFP_KERNEL | __GFP_HIGHMEM);
  
  	return __vmalloc(size, gfp);
  }
  
  static void snd_dma_vmalloc_free(struct snd_dma_buffer *dmab)
  {
  	vfree(dmab->area);
  }
  
  static int snd_dma_vmalloc_mmap(struct snd_dma_buffer *dmab,
  				struct vm_area_struct *area)
  {
  	return remap_vmalloc_range(area, dmab->area, 0);
  }
  
  #define get_vmalloc_page_addr(dmab, offset) \
  	page_to_phys(vmalloc_to_page((dmab)->area + (offset)))
  
  static dma_addr_t snd_dma_vmalloc_get_addr(struct snd_dma_buffer *dmab,
  					   size_t offset)
  {
  	return get_vmalloc_page_addr(dmab, offset) + offset % PAGE_SIZE;
  }
  
  static struct page *snd_dma_vmalloc_get_page(struct snd_dma_buffer *dmab,
  					     size_t offset)
  {
  	return vmalloc_to_page(dmab->area + offset);
  }
  
  static unsigned int
  snd_dma_vmalloc_get_chunk_size(struct snd_dma_buffer *dmab,
  			       unsigned int ofs, unsigned int size)
  {
  	unsigned int start, end;
  	unsigned long addr;
  
  	start = ALIGN_DOWN(ofs, PAGE_SIZE);
  	end = ofs + size - 1; /* the last byte address */
  	/* check page continuity */
  	addr = get_vmalloc_page_addr(dmab, start);
  	for (;;) {
  		start += PAGE_SIZE;
  		if (start > end)
  			break;
  		addr += PAGE_SIZE;
  		if (get_vmalloc_page_addr(dmab, start) != addr)
  			return start - ofs;
  	}
  	/* ok, all on continuous pages */
  	return size;
  }
  
  static const struct snd_malloc_ops snd_dma_vmalloc_ops = {
  	.alloc = snd_dma_vmalloc_alloc,
  	.free = snd_dma_vmalloc_free,
  	.mmap = snd_dma_vmalloc_mmap,
  	.get_addr = snd_dma_vmalloc_get_addr,
  	.get_page = snd_dma_vmalloc_get_page,
  	.get_chunk_size = snd_dma_vmalloc_get_chunk_size,
  };
  
  #ifdef CONFIG_HAS_DMA
  /*
   * IRAM allocator
   */
  #ifdef CONFIG_GENERIC_ALLOCATOR
  static void *snd_dma_iram_alloc(struct snd_dma_buffer *dmab, size_t size)
  {
  	struct device *dev = dmab->dev.dev;
  	struct gen_pool *pool;
  	void *p;
  
  	if (dev->of_node) {
  		pool = of_gen_pool_get(dev->of_node, "iram", 0);
  		/* Assign the pool into private_data field */
  		dmab->private_data = pool;
  
  		p = gen_pool_dma_alloc_align(pool, size, &dmab->addr, PAGE_SIZE);
  		if (p)
  			return p;
  	}
  
  	/* Internal memory might have limited size and no enough space,
  	 * so if we fail to malloc, try to fetch memory traditionally.
  	 */
  	dmab->dev.type = SNDRV_DMA_TYPE_DEV;
  	return __snd_dma_alloc_pages(dmab, size);
  }
  
  static void snd_dma_iram_free(struct snd_dma_buffer *dmab)
  {
  	struct gen_pool *pool = dmab->private_data;
  
  	if (pool && dmab->area)
  		gen_pool_free(pool, (unsigned long)dmab->area, dmab->bytes);
  }
  
  static int snd_dma_iram_mmap(struct snd_dma_buffer *dmab,
  			     struct vm_area_struct *area)
  {
  	area->vm_page_prot = pgprot_writecombine(area->vm_page_prot);
  	return remap_pfn_range(area, area->vm_start,
  			       dmab->addr >> PAGE_SHIFT,
  			       area->vm_end - area->vm_start,
  			       area->vm_page_prot);
  }
  
  static const struct snd_malloc_ops snd_dma_iram_ops = {
  	.alloc = snd_dma_iram_alloc,
  	.free = snd_dma_iram_free,
  	.mmap = snd_dma_iram_mmap,
  };
  #endif /* CONFIG_GENERIC_ALLOCATOR */
  
  #define DEFAULT_GFP \
  	(GFP_KERNEL | \
  	 __GFP_COMP |    /* compound page lets parts be mapped */ \
  	 __GFP_NORETRY | /* don't trigger OOM-killer */ \
  	 __GFP_NOWARN)   /* no stack trace print - this call is non-critical */
  
  /*
   * Coherent device pages allocator
   */
  static void *snd_dma_dev_alloc(struct snd_dma_buffer *dmab, size_t size)
  {
  	void *p;
  
  	p = dma_alloc_coherent(dmab->dev.dev, size, &dmab->addr, DEFAULT_GFP);
  #ifdef CONFIG_X86
  	if (p && dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC)
  		set_memory_wc((unsigned long)p, PAGE_ALIGN(size) >> PAGE_SHIFT);
  #endif
  	return p;
  }
  
  static void snd_dma_dev_free(struct snd_dma_buffer *dmab)
  {
  #ifdef CONFIG_X86
  	if (dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC)
  		set_memory_wb((unsigned long)dmab->area,
  			      PAGE_ALIGN(dmab->bytes) >> PAGE_SHIFT);
  #endif
  	dma_free_coherent(dmab->dev.dev, dmab->bytes, dmab->area, dmab->addr);
  }
  
  static int snd_dma_dev_mmap(struct snd_dma_buffer *dmab,
  			    struct vm_area_struct *area)
  {
  #ifdef CONFIG_X86
  	if (dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC)
  		area->vm_page_prot = pgprot_writecombine(area->vm_page_prot);
  #endif
  	return dma_mmap_coherent(dmab->dev.dev, area,
  				 dmab->area, dmab->addr, dmab->bytes);
  }
  
  static const struct snd_malloc_ops snd_dma_dev_ops = {
  	.alloc = snd_dma_dev_alloc,
  	.free = snd_dma_dev_free,
  	.mmap = snd_dma_dev_mmap,
  };
  
  /*
   * Write-combined pages
   */
  #ifdef CONFIG_X86
  /* On x86, share the same ops as the standard dev ops */
  #define snd_dma_wc_ops	snd_dma_dev_ops
  #else /* CONFIG_X86 */
  static void *snd_dma_wc_alloc(struct snd_dma_buffer *dmab, size_t size)
  {
  	return dma_alloc_wc(dmab->dev.dev, size, &dmab->addr, DEFAULT_GFP);
  }
  
  static void snd_dma_wc_free(struct snd_dma_buffer *dmab)
  {
  	dma_free_wc(dmab->dev.dev, dmab->bytes, dmab->area, dmab->addr);
  }
  
  static int snd_dma_wc_mmap(struct snd_dma_buffer *dmab,
  			   struct vm_area_struct *area)
  {
  	return dma_mmap_wc(dmab->dev.dev, area,
  			   dmab->area, dmab->addr, dmab->bytes);
  }
  
  static const struct snd_malloc_ops snd_dma_wc_ops = {
  	.alloc = snd_dma_wc_alloc,
  	.free = snd_dma_wc_free,
  	.mmap = snd_dma_wc_mmap,
  };
  #endif /* CONFIG_X86 */
  
  /*
   * Non-contiguous pages allocator
   */
  static void *snd_dma_noncontig_alloc(struct snd_dma_buffer *dmab, size_t size)
  {
  	struct sg_table *sgt;
  	void *p;
  
  	sgt = dma_alloc_noncontiguous(dmab->dev.dev, size, dmab->dev.dir,
  				      DEFAULT_GFP, 0);
  	if (!sgt)
  		return NULL;
  	dmab->dev.need_sync = dma_need_sync(dmab->dev.dev, dmab->dev.dir);
  	p = dma_vmap_noncontiguous(dmab->dev.dev, size, sgt);
  	if (p)
  		dmab->private_data = sgt;
  	else
  		dma_free_noncontiguous(dmab->dev.dev, size, sgt, dmab->dev.dir);
  	return p;
  }
  
  static void snd_dma_noncontig_free(struct snd_dma_buffer *dmab)
  {
  	dma_vunmap_noncontiguous(dmab->dev.dev, dmab->area);
  	dma_free_noncontiguous(dmab->dev.dev, dmab->bytes, dmab->private_data,
  			       dmab->dev.dir);
  }
  
  static int snd_dma_noncontig_mmap(struct snd_dma_buffer *dmab,
  				  struct vm_area_struct *area)
  {
  	return dma_mmap_noncontiguous(dmab->dev.dev, area,
  				      dmab->bytes, dmab->private_data);
  }
  
  static void snd_dma_noncontig_sync(struct snd_dma_buffer *dmab,
  				   enum snd_dma_sync_mode mode)
  {
  	if (mode == SNDRV_DMA_SYNC_CPU) {
  		if (dmab->dev.dir == DMA_TO_DEVICE)
  			return;
  		dma_sync_sgtable_for_cpu(dmab->dev.dev, dmab->private_data,
  					 dmab->dev.dir);
  		invalidate_kernel_vmap_range(dmab->area, dmab->bytes);
  	} else {
  		if (dmab->dev.dir == DMA_FROM_DEVICE)
  			return;
  		flush_kernel_vmap_range(dmab->area, dmab->bytes);
  		dma_sync_sgtable_for_device(dmab->dev.dev, dmab->private_data,
  					    dmab->dev.dir);
  	}
  }
  
  static inline void snd_dma_noncontig_iter_set(struct snd_dma_buffer *dmab,
  					      struct sg_page_iter *piter,
  					      size_t offset)
  {
  	struct sg_table *sgt = dmab->private_data;
  
  	__sg_page_iter_start(piter, sgt->sgl, sgt->orig_nents,
  			     offset >> PAGE_SHIFT);
  }
  
  static dma_addr_t snd_dma_noncontig_get_addr(struct snd_dma_buffer *dmab,
  					     size_t offset)
  {
  	struct sg_dma_page_iter iter;
  
  	snd_dma_noncontig_iter_set(dmab, &iter.base, offset);
  	__sg_page_iter_dma_next(&iter);
  	return sg_page_iter_dma_address(&iter) + offset % PAGE_SIZE;
  }
  
  static struct page *snd_dma_noncontig_get_page(struct snd_dma_buffer *dmab,
  					       size_t offset)
  {
  	struct sg_page_iter iter;
  
  	snd_dma_noncontig_iter_set(dmab, &iter, offset);
  	__sg_page_iter_next(&iter);
  	return sg_page_iter_page(&iter);
  }
  
  static unsigned int
  snd_dma_noncontig_get_chunk_size(struct snd_dma_buffer *dmab,
  				 unsigned int ofs, unsigned int size)
  {
  	struct sg_dma_page_iter iter;
  	unsigned int start, end;
  	unsigned long addr;
  
  	start = ALIGN_DOWN(ofs, PAGE_SIZE);
  	end = ofs + size - 1; /* the last byte address */
  	snd_dma_noncontig_iter_set(dmab, &iter.base, start);
  	if (!__sg_page_iter_dma_next(&iter))
  		return 0;
  	/* check page continuity */
  	addr = sg_page_iter_dma_address(&iter);
  	for (;;) {
  		start += PAGE_SIZE;
  		if (start > end)
  			break;
  		addr += PAGE_SIZE;
  		if (!__sg_page_iter_dma_next(&iter) ||
  		    sg_page_iter_dma_address(&iter) != addr)
  			return start - ofs;
  	}
  	/* ok, all on continuous pages */
  	return size;
  }
  
  static const struct snd_malloc_ops snd_dma_noncontig_ops = {
  	.alloc = snd_dma_noncontig_alloc,
  	.free = snd_dma_noncontig_free,
  	.mmap = snd_dma_noncontig_mmap,
  	.sync = snd_dma_noncontig_sync,
  	.get_addr = snd_dma_noncontig_get_addr,
  	.get_page = snd_dma_noncontig_get_page,
  	.get_chunk_size = snd_dma_noncontig_get_chunk_size,
  };
  
  /* x86-specific SG-buffer with WC pages */
  #ifdef CONFIG_SND_DMA_SGBUF
  #define sg_wc_address(it) ((unsigned long)page_address(sg_page_iter_page(it)))
  
  static void *snd_dma_sg_wc_alloc(struct snd_dma_buffer *dmab, size_t size)
  {
  	void *p = snd_dma_noncontig_alloc(dmab, size);
  	struct sg_table *sgt = dmab->private_data;
  	struct sg_page_iter iter;
  
  	if (!p)
  		return NULL;
  	for_each_sgtable_page(sgt, &iter, 0)
  		set_memory_wc(sg_wc_address(&iter), 1);
  	return p;
  }
  
  static void snd_dma_sg_wc_free(struct snd_dma_buffer *dmab)
  {
  	struct sg_table *sgt = dmab->private_data;
  	struct sg_page_iter iter;
  
  	for_each_sgtable_page(sgt, &iter, 0)
  		set_memory_wb(sg_wc_address(&iter), 1);
  	snd_dma_noncontig_free(dmab);
  }
  
  static int snd_dma_sg_wc_mmap(struct snd_dma_buffer *dmab,
  			      struct vm_area_struct *area)
  {
  	area->vm_page_prot = pgprot_writecombine(area->vm_page_prot);
  	return dma_mmap_noncontiguous(dmab->dev.dev, area,
  				      dmab->bytes, dmab->private_data);
  }
  
  static const struct snd_malloc_ops snd_dma_sg_wc_ops = {
  	.alloc = snd_dma_sg_wc_alloc,
  	.free = snd_dma_sg_wc_free,
  	.mmap = snd_dma_sg_wc_mmap,
  	.sync = snd_dma_noncontig_sync,
  	.get_addr = snd_dma_noncontig_get_addr,
  	.get_page = snd_dma_noncontig_get_page,
  	.get_chunk_size = snd_dma_noncontig_get_chunk_size,
  };
  #endif /* CONFIG_SND_DMA_SGBUF */
  
  /*
   * Non-coherent pages allocator
   */
  static void *snd_dma_noncoherent_alloc(struct snd_dma_buffer *dmab, size_t size)
  {
  	dmab->dev.need_sync = dma_need_sync(dmab->dev.dev, dmab->dev.dir);
  	return dma_alloc_noncoherent(dmab->dev.dev, size, &dmab->addr,
  				     dmab->dev.dir, DEFAULT_GFP);
  }
  
  static void snd_dma_noncoherent_free(struct snd_dma_buffer *dmab)
  {
  	dma_free_noncoherent(dmab->dev.dev, dmab->bytes, dmab->area,
  			     dmab->addr, dmab->dev.dir);
  }
  
  static int snd_dma_noncoherent_mmap(struct snd_dma_buffer *dmab,
  				    struct vm_area_struct *area)
  {
  	area->vm_page_prot = vm_get_page_prot(area->vm_flags);
  	return dma_mmap_pages(dmab->dev.dev, area,
  			      area->vm_end - area->vm_start,
  			      virt_to_page(dmab->area));
  }
  
  static void snd_dma_noncoherent_sync(struct snd_dma_buffer *dmab,
  				     enum snd_dma_sync_mode mode)
  {
  	if (mode == SNDRV_DMA_SYNC_CPU) {
  		if (dmab->dev.dir != DMA_TO_DEVICE)
  			dma_sync_single_for_cpu(dmab->dev.dev, dmab->addr,
  						dmab->bytes, dmab->dev.dir);
  	} else {
  		if (dmab->dev.dir != DMA_FROM_DEVICE)
  			dma_sync_single_for_device(dmab->dev.dev, dmab->addr,
  						   dmab->bytes, dmab->dev.dir);
  	}
  }
  
  static const struct snd_malloc_ops snd_dma_noncoherent_ops = {
  	.alloc = snd_dma_noncoherent_alloc,
  	.free = snd_dma_noncoherent_free,
  	.mmap = snd_dma_noncoherent_mmap,
  	.sync = snd_dma_noncoherent_sync,
  };
  
  #endif /* CONFIG_HAS_DMA */
  
  /*
   * Entry points
   */
  static const struct snd_malloc_ops *dma_ops[] = {
  	[SNDRV_DMA_TYPE_CONTINUOUS] = &snd_dma_continuous_ops,
  	[SNDRV_DMA_TYPE_VMALLOC] = &snd_dma_vmalloc_ops,
  #ifdef CONFIG_HAS_DMA
  	[SNDRV_DMA_TYPE_DEV] = &snd_dma_dev_ops,
  	[SNDRV_DMA_TYPE_DEV_WC] = &snd_dma_wc_ops,
  	[SNDRV_DMA_TYPE_NONCONTIG] = &snd_dma_noncontig_ops,
  	[SNDRV_DMA_TYPE_NONCOHERENT] = &snd_dma_noncoherent_ops,
  #ifdef CONFIG_SND_DMA_SGBUF
  	[SNDRV_DMA_TYPE_DEV_WC_SG] = &snd_dma_sg_wc_ops,
  #endif
  #ifdef CONFIG_GENERIC_ALLOCATOR
  	[SNDRV_DMA_TYPE_DEV_IRAM] = &snd_dma_iram_ops,
  #endif /* CONFIG_GENERIC_ALLOCATOR */
  #endif /* CONFIG_HAS_DMA */
  };
  
  static const struct snd_malloc_ops *snd_dma_get_ops(struct snd_dma_buffer *dmab)
  {
  	if (WARN_ON_ONCE(!dmab))
  		return NULL;
  	if (WARN_ON_ONCE(dmab->dev.type <= SNDRV_DMA_TYPE_UNKNOWN ||
  			 dmab->dev.type >= ARRAY_SIZE(dma_ops)))
  		return NULL;
  	return dma_ops[dmab->dev.type];
  }
  