sound/core/pcm_memory.c - kernel/panda - Git at Google

 /*
  *  Digital Audio (PCM) abstract layer
  *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
  *
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
  *   the Free Software Foundation; either version 2 of the License, or
  *   (at your option) any later version.
  *
  *   This program is distributed in the hope that it will be useful,
  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  *   GNU General Public License for more details.
  *
  *   You should have received a copy of the GNU General Public License
  *   along with this program; if not, write to the Free Software
  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  *
  */

 #include <asm/io.h>
 #include <linux/time.h>
 #include <linux/init.h>
 #include <linux/moduleparam.h>
 #include <sound/core.h>
 #include <sound/pcm.h>
 #include <sound/info.h>
 #include <sound/initval.h>

 static int preallocate_dma = 1;
 module_param(preallocate_dma, int, 0444);
 MODULE_PARM_DESC(preallocate_dma, "Preallocate DMA memory when the PCM devices are initialized.");

 static int maximum_substreams = 4;
 module_param(maximum_substreams, int, 0444);
 MODULE_PARM_DESC(maximum_substreams, "Maximum substreams with preallocated DMA memory.");

 static const size_t snd_minimum_buffer = 16384;


 /*
  * try to allocate as the large pages as possible.
  * stores the resultant memory size in *res_size.
  *
  * the minimum size is snd_minimum_buffer.  it should be power of 2.
  */
 static int preallocate_pcm_pages(struct snd_pcm_substream *substream, size_t size)
 {
 	struct snd_dma_buffer *dmab = &substream->dma_buffer;
 	int err;

 	/* already reserved? */
 	if (snd_dma_get_reserved_buf(dmab, substream->dma_buf_id) > 0) {
 		if (dmab->bytes >= size)
 			return 0; /* yes */
 		/* no, free the reserved block */
 		snd_dma_free_pages(dmab);
 		dmab->bytes = 0;
 	}

 	do {
 		if ((err = snd_dma_alloc_pages(dmab->dev.type, dmab->dev.dev,
 					       size, dmab)) < 0) {
 			if (err != -ENOMEM)
 				return err; /* fatal error */
 		} else
 			return 0;
 		size >>= 1;
 	} while (size >= snd_minimum_buffer);
 	dmab->bytes = 0; /* tell error */
 	return 0;
 }

 /*
  * release the preallocated buffer if not yet done.
  */
 static void snd_pcm_lib_preallocate_dma_free(struct snd_pcm_substream *substream)
 {
 	if (substream->dma_buffer.area == NULL)
 		return;
 	if (substream->dma_buf_id)
 		snd_dma_reserve_buf(&substream->dma_buffer, substream->dma_buf_id);
 	else
 		snd_dma_free_pages(&substream->dma_buffer);
 	substream->dma_buffer.area = NULL;
 }

 /**
  * snd_pcm_lib_preallocate_free - release the preallocated buffer of the specified substream.
  * @substream: the pcm substream instance
  *
  * Releases the pre-allocated buffer of the given substream.
  *
  * Returns zero if successful, or a negative error code on failure.
  */
 int snd_pcm_lib_preallocate_free(struct snd_pcm_substream *substream)
 {
 	snd_pcm_lib_preallocate_dma_free(substream);
 #ifdef CONFIG_SND_VERBOSE_PROCFS
 	snd_info_free_entry(substream->proc_prealloc_max_entry);
 	substream->proc_prealloc_max_entry = NULL;
 	snd_info_free_entry(substream->proc_prealloc_entry);
 	substream->proc_prealloc_entry = NULL;
 #endif
 	return 0;
 }

 /**
  * snd_pcm_lib_preallocate_free_for_all - release all pre-allocated buffers on the pcm
  * @pcm: the pcm instance
  *
  * Releases all the pre-allocated buffers on the given pcm.
  *
  * Returns zero if successful, or a negative error code on failure.
  */
 int snd_pcm_lib_preallocate_free_for_all(struct snd_pcm *pcm)
 {
 	struct snd_pcm_substream *substream;
 	int stream;

 	for (stream = 0; stream < 2; stream++)
 		for (substream = pcm->streams[stream].substream; substream; substream = substream->next)
 			snd_pcm_lib_preallocate_free(substream);
 	return 0;
 }

 EXPORT_SYMBOL(snd_pcm_lib_preallocate_free_for_all);

 #ifdef CONFIG_SND_VERBOSE_PROCFS
 /*
  * read callback for prealloc proc file
  *
  * prints the current allocated size in kB.
  */
 static void snd_pcm_lib_preallocate_proc_read(struct snd_info_entry *entry,
 					      struct snd_info_buffer *buffer)
 {
 	struct snd_pcm_substream *substream = entry->private_data;
 	snd_iprintf(buffer, "%lu\n", (unsigned long) substream->dma_buffer.bytes / 1024);
 }

 /*
  * read callback for prealloc_max proc file
  *
  * prints the maximum allowed size in kB.
  */
 static void snd_pcm_lib_preallocate_max_proc_read(struct snd_info_entry *entry,
 						  struct snd_info_buffer *buffer)
 {
 	struct snd_pcm_substream *substream = entry->private_data;
 	snd_iprintf(buffer, "%lu\n", (unsigned long) substream->dma_max / 1024);
 }

 /*
  * write callback for prealloc proc file
  *
  * accepts the preallocation size in kB.
  */
 static void snd_pcm_lib_preallocate_proc_write(struct snd_info_entry *entry,
 					       struct snd_info_buffer *buffer)
 {
 	struct snd_pcm_substream *substream = entry->private_data;
 	char line[64], str[64];
 	size_t size;
 	struct snd_dma_buffer new_dmab;

 	if (substream->runtime) {
 		buffer->error = -EBUSY;
 		return;
 	}
 	if (!snd_info_get_line(buffer, line, sizeof(line))) {
 		snd_info_get_str(str, line, sizeof(str));
 		size = simple_strtoul(str, NULL, 10) * 1024;
 		if ((size != 0 && size < 8192) || size > substream->dma_max) {
 			buffer->error = -EINVAL;
 			return;
 		}
 		if (substream->dma_buffer.bytes == size)
 			return;
 		memset(&new_dmab, 0, sizeof(new_dmab));
 		new_dmab.dev = substream->dma_buffer.dev;
 		if (size > 0) {
 			if (snd_dma_alloc_pages(substream->dma_buffer.dev.type,
 						substream->dma_buffer.dev.dev,
 						size, &new_dmab) < 0) {
 				buffer->error = -ENOMEM;
 				return;
 			}
 			substream->buffer_bytes_max = size;
 		} else {
 			substream->buffer_bytes_max = UINT_MAX;
 		}
 		if (substream->dma_buffer.area)
 			snd_dma_free_pages(&substream->dma_buffer);
 		substream->dma_buffer = new_dmab;
 	} else {
 		buffer->error = -EINVAL;
 	}
 }

 static inline void preallocate_info_init(struct snd_pcm_substream *substream)
 {
 	struct snd_info_entry *entry;

 	if ((entry = snd_info_create_card_entry(substream->pcm->card, "prealloc", substream->proc_root)) != NULL) {
 		entry->c.text.read = snd_pcm_lib_preallocate_proc_read;
 		entry->c.text.write = snd_pcm_lib_preallocate_proc_write;
 		entry->mode |= S_IWUSR;
 		entry->private_data = substream;
 		if (snd_info_register(entry) < 0) {
 			snd_info_free_entry(entry);
 			entry = NULL;
 		}
 	}
 	substream->proc_prealloc_entry = entry;
 	if ((entry = snd_info_create_card_entry(substream->pcm->card, "prealloc_max", substream->proc_root)) != NULL) {
 		entry->c.text.read = snd_pcm_lib_preallocate_max_proc_read;
 		entry->private_data = substream;
 		if (snd_info_register(entry) < 0) {
 			snd_info_free_entry(entry);
 			entry = NULL;
 		}
 	}
 	substream->proc_prealloc_max_entry = entry;
 }

 #else /* !CONFIG_SND_VERBOSE_PROCFS */
 #define preallocate_info_init(s)
 #endif /* CONFIG_SND_VERBOSE_PROCFS */

 /*
  * pre-allocate the buffer and create a proc file for the substream
  */
 static int snd_pcm_lib_preallocate_pages1(struct snd_pcm_substream *substream,
 					  size_t size, size_t max)
 {

 	if (size > 0 && preallocate_dma && substream->number < maximum_substreams)
 		preallocate_pcm_pages(substream, size);

 	if (substream->dma_buffer.bytes > 0)
 		substream->buffer_bytes_max = substream->dma_buffer.bytes;
 	substream->dma_max = max;
 	preallocate_info_init(substream);
 	return 0;
 }


 /**
  * snd_pcm_lib_preallocate_pages - pre-allocation for the given DMA type
  * @substream: the pcm substream instance
  * @type: DMA type (SNDRV_DMA_TYPE_*)
  * @data: DMA type dependant data
  * @size: the requested pre-allocation size in bytes
  * @max: the max. allowed pre-allocation size
  *
  * Do pre-allocation for the given DMA buffer type.
  *
  * When substream->dma_buf_id is set, the function tries to look for
  * the reserved buffer, and the buffer is not freed but reserved at
  * destruction time.  The dma_buf_id must be unique for all systems
  * (in the same DMA buffer type) e.g. using snd_dma_pci_buf_id().
  *
  * Returns zero if successful, or a negative error code on failure.
  */
 int snd_pcm_lib_preallocate_pages(struct snd_pcm_substream *substream,
 				  int type, struct device *data,
 				  size_t size, size_t max)
 {
 	substream->dma_buffer.dev.type = type;
 	substream->dma_buffer.dev.dev = data;
 	return snd_pcm_lib_preallocate_pages1(substream, size, max);
 }

 EXPORT_SYMBOL(snd_pcm_lib_preallocate_pages);

 /**
  * snd_pcm_lib_preallocate_pages_for_all - pre-allocation for continous memory type (all substreams)
  * @pcm: the pcm instance
  * @type: DMA type (SNDRV_DMA_TYPE_*)
  * @data: DMA type dependant data
  * @size: the requested pre-allocation size in bytes
  * @max: the max. allowed pre-allocation size
  *
  * Do pre-allocation to all substreams of the given pcm for the
  * specified DMA type.
  *
  * Returns zero if successful, or a negative error code on failure.
  */
 int snd_pcm_lib_preallocate_pages_for_all(struct snd_pcm *pcm,
 					  int type, void *data,
 					  size_t size, size_t max)
 {
 	struct snd_pcm_substream *substream;
 	int stream, err;

 	for (stream = 0; stream < 2; stream++)
 		for (substream = pcm->streams[stream].substream; substream; substream = substream->next)
 			if ((err = snd_pcm_lib_preallocate_pages(substream, type, data, size, max)) < 0)
 				return err;
 	return 0;
 }

 EXPORT_SYMBOL(snd_pcm_lib_preallocate_pages_for_all);

 /**
  * snd_pcm_sgbuf_ops_page - get the page struct at the given offset
  * @substream: the pcm substream instance
  * @offset: the buffer offset
  *
  * Returns the page struct at the given buffer offset.
  * Used as the page callback of PCM ops.
  */
 struct page *snd_pcm_sgbuf_ops_page(struct snd_pcm_substream *substream, unsigned long offset)
 {
 	struct snd_sg_buf *sgbuf = snd_pcm_substream_sgbuf(substream);

 	unsigned int idx = offset >> PAGE_SHIFT;
 	if (idx >= (unsigned int)sgbuf->pages)
 		return NULL;
 	return sgbuf->page_table[idx];
 }

 EXPORT_SYMBOL(snd_pcm_sgbuf_ops_page);

 /*
  * compute the max chunk size with continuous pages on sg-buffer
  */
 unsigned int snd_pcm_sgbuf_get_chunk_size(struct snd_pcm_substream *substream,
 					  unsigned int ofs, unsigned int size)
 {
 	struct snd_sg_buf *sg = snd_pcm_substream_sgbuf(substream);
 	unsigned int start, end, pg;

 	start = ofs >> PAGE_SHIFT;
 	end = (ofs + size - 1) >> PAGE_SHIFT;
 	/* check page continuity */
 	pg = sg->table[start].addr >> PAGE_SHIFT;
 	for (;;) {
 		start++;
 		if (start > end)
 			break;
 		pg++;
 		if ((sg->table[start].addr >> PAGE_SHIFT) != pg)
 			return (start << PAGE_SHIFT) - ofs;
 	}
 	/* ok, all on continuous pages */
 	return size;
 }
 EXPORT_SYMBOL(snd_pcm_sgbuf_get_chunk_size);

 /**
  * snd_pcm_lib_malloc_pages - allocate the DMA buffer
  * @substream: the substream to allocate the DMA buffer to
  * @size: the requested buffer size in bytes
  *
  * Allocates the DMA buffer on the BUS type given earlier to
  * snd_pcm_lib_preallocate_xxx_pages().
  *
  * Returns 1 if the buffer is changed, 0 if not changed, or a negative
  * code on failure.
  */
 int snd_pcm_lib_malloc_pages(struct snd_pcm_substream *substream, size_t size)
 {
 	struct snd_pcm_runtime *runtime;
 	struct snd_dma_buffer *dmab = NULL;

 	if (PCM_RUNTIME_CHECK(substream))
 		return -EINVAL;
 	if (snd_BUG_ON(substream->dma_buffer.dev.type ==
 		       SNDRV_DMA_TYPE_UNKNOWN))
 		return -EINVAL;
 	runtime = substream->runtime;

 	if (runtime->dma_buffer_p) {
 		/* perphaps, we might free the large DMA memory region
 		   to save some space here, but the actual solution
 		   costs us less time */
 		if (runtime->dma_buffer_p->bytes >= size) {
 			runtime->dma_bytes = size;
 			return 0;	/* ok, do not change */
 		}
 		snd_pcm_lib_free_pages(substream);
 	}
 	if (substream->dma_buffer.area != NULL &&
 	    substream->dma_buffer.bytes >= size) {
 		dmab = &substream->dma_buffer; /* use the pre-allocated buffer */
 	} else {
 		dmab = kzalloc(sizeof(*dmab), GFP_KERNEL);
 		if (! dmab)
 			return -ENOMEM;
 		dmab->dev = substream->dma_buffer.dev;
 		if (snd_dma_alloc_pages(substream->dma_buffer.dev.type,
 					substream->dma_buffer.dev.dev,
 					size, dmab) < 0) {
 			kfree(dmab);
 			return -ENOMEM;
 		}
 	}
 	snd_pcm_set_runtime_buffer(substream, dmab);
 	runtime->dma_bytes = size;
 	return 1;			/* area was changed */
 }

 EXPORT_SYMBOL(snd_pcm_lib_malloc_pages);

 /**
  * snd_pcm_lib_free_pages - release the allocated DMA buffer.
  * @substream: the substream to release the DMA buffer
  *
  * Releases the DMA buffer allocated via snd_pcm_lib_malloc_pages().
  *
  * Returns zero if successful, or a negative error code on failure.
  */
 int snd_pcm_lib_free_pages(struct snd_pcm_substream *substream)
 {
 	struct snd_pcm_runtime *runtime;

 	if (PCM_RUNTIME_CHECK(substream))
 		return -EINVAL;
 	runtime = substream->runtime;
 	if (runtime->dma_area == NULL)
 		return 0;
 	if (runtime->dma_buffer_p != &substream->dma_buffer) {
 		/* it's a newly allocated buffer.  release it now. */
 		snd_dma_free_pages(runtime->dma_buffer_p);
 		kfree(runtime->dma_buffer_p);
 	}
 	snd_pcm_set_runtime_buffer(substream, NULL);
 	return 0;
 }

 EXPORT_SYMBOL(snd_pcm_lib_free_pages);
	/*
	* Digital Audio (PCM) abstract layer
	* Copyright (c) by Jaroslav Kysela <perex@perex.cz>
	*
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	*
	*/

	#include <asm/io.h>
	#include <linux/time.h>
	#include <linux/init.h>
	#include <linux/moduleparam.h>
	#include <sound/core.h>
	#include <sound/pcm.h>
	#include <sound/info.h>
	#include <sound/initval.h>

	static int preallocate_dma = 1;
	module_param(preallocate_dma, int, 0444);
	MODULE_PARM_DESC(preallocate_dma, "Preallocate DMA memory when the PCM devices are initialized.");

	static int maximum_substreams = 4;
	module_param(maximum_substreams, int, 0444);
	MODULE_PARM_DESC(maximum_substreams, "Maximum substreams with preallocated DMA memory.");

	static const size_t snd_minimum_buffer = 16384;


	/*
	* try to allocate as the large pages as possible.
	* stores the resultant memory size in *res_size.
	*
	* the minimum size is snd_minimum_buffer. it should be power of 2.
	*/
	static int preallocate_pcm_pages(struct snd_pcm_substream *substream, size_t size)
	{
	struct snd_dma_buffer *dmab = &substream->dma_buffer;
	int err;

	/* already reserved? */
	if (snd_dma_get_reserved_buf(dmab, substream->dma_buf_id) > 0) {
	if (dmab->bytes >= size)
	return 0; /* yes */
	/* no, free the reserved block */
	snd_dma_free_pages(dmab);
	dmab->bytes = 0;
	}

	do {
	if ((err = snd_dma_alloc_pages(dmab->dev.type, dmab->dev.dev,
	size, dmab)) < 0) {
	if (err != -ENOMEM)
	return err; /* fatal error */
	} else
	return 0;
	size >>= 1;
	} while (size >= snd_minimum_buffer);
	dmab->bytes = 0; /* tell error */
	return 0;
	}

	/*
	* release the preallocated buffer if not yet done.
	*/
	static void snd_pcm_lib_preallocate_dma_free(struct snd_pcm_substream *substream)
	{
	if (substream->dma_buffer.area == NULL)
	return;
	if (substream->dma_buf_id)
	snd_dma_reserve_buf(&substream->dma_buffer, substream->dma_buf_id);
	else
	snd_dma_free_pages(&substream->dma_buffer);
	substream->dma_buffer.area = NULL;
	}

	/**
	* snd_pcm_lib_preallocate_free - release the preallocated buffer of the specified substream.
	* @substream: the pcm substream instance
	*
	* Releases the pre-allocated buffer of the given substream.
	*
	* Returns zero if successful, or a negative error code on failure.
	*/
	int snd_pcm_lib_preallocate_free(struct snd_pcm_substream *substream)
	{
	snd_pcm_lib_preallocate_dma_free(substream);
	#ifdef CONFIG_SND_VERBOSE_PROCFS
	snd_info_free_entry(substream->proc_prealloc_max_entry);
	substream->proc_prealloc_max_entry = NULL;
	snd_info_free_entry(substream->proc_prealloc_entry);
	substream->proc_prealloc_entry = NULL;
	#endif
	return 0;
	}

	/**
	* snd_pcm_lib_preallocate_free_for_all - release all pre-allocated buffers on the pcm
	* @pcm: the pcm instance
	*
	* Releases all the pre-allocated buffers on the given pcm.
	*
	* Returns zero if successful, or a negative error code on failure.
	*/
	int snd_pcm_lib_preallocate_free_for_all(struct snd_pcm *pcm)
	{
	struct snd_pcm_substream *substream;
	int stream;

	for (stream = 0; stream < 2; stream++)
	for (substream = pcm->streams[stream].substream; substream; substream = substream->next)
	snd_pcm_lib_preallocate_free(substream);
	return 0;
	}

	EXPORT_SYMBOL(snd_pcm_lib_preallocate_free_for_all);

	#ifdef CONFIG_SND_VERBOSE_PROCFS
	/*
	* read callback for prealloc proc file
	*
	* prints the current allocated size in kB.
	*/
	static void snd_pcm_lib_preallocate_proc_read(struct snd_info_entry *entry,
	struct snd_info_buffer *buffer)
	{
	struct snd_pcm_substream *substream = entry->private_data;
	snd_iprintf(buffer, "%lu\n", (unsigned long) substream->dma_buffer.bytes / 1024);
	}

	/*
	* read callback for prealloc_max proc file
	*
	* prints the maximum allowed size in kB.
	*/
	static void snd_pcm_lib_preallocate_max_proc_read(struct snd_info_entry *entry,
	struct snd_info_buffer *buffer)
	{
	struct snd_pcm_substream *substream = entry->private_data;
	snd_iprintf(buffer, "%lu\n", (unsigned long) substream->dma_max / 1024);
	}

	/*
	* write callback for prealloc proc file
	*
	* accepts the preallocation size in kB.
	*/
	static void snd_pcm_lib_preallocate_proc_write(struct snd_info_entry *entry,
	struct snd_info_buffer *buffer)
	{
	struct snd_pcm_substream *substream = entry->private_data;
	char line[64], str[64];
	size_t size;
	struct snd_dma_buffer new_dmab;

	if (substream->runtime) {
	buffer->error = -EBUSY;
	return;
	}
	if (!snd_info_get_line(buffer, line, sizeof(line))) {
	snd_info_get_str(str, line, sizeof(str));
	size = simple_strtoul(str, NULL, 10) * 1024;
	if ((size != 0 && size < 8192) \|\| size > substream->dma_max) {
	buffer->error = -EINVAL;
	return;
	}
	if (substream->dma_buffer.bytes == size)
	return;
	memset(&new_dmab, 0, sizeof(new_dmab));
	new_dmab.dev = substream->dma_buffer.dev;
	if (size > 0) {
	if (snd_dma_alloc_pages(substream->dma_buffer.dev.type,
	substream->dma_buffer.dev.dev,
	size, &new_dmab) < 0) {
	buffer->error = -ENOMEM;
	return;
	}
	substream->buffer_bytes_max = size;
	} else {
	substream->buffer_bytes_max = UINT_MAX;
	}
	if (substream->dma_buffer.area)
	snd_dma_free_pages(&substream->dma_buffer);
	substream->dma_buffer = new_dmab;
	} else {
	buffer->error = -EINVAL;
	}
	}

	static inline void preallocate_info_init(struct snd_pcm_substream *substream)
	{
	struct snd_info_entry *entry;

	if ((entry = snd_info_create_card_entry(substream->pcm->card, "prealloc", substream->proc_root)) != NULL) {
	entry->c.text.read = snd_pcm_lib_preallocate_proc_read;
	entry->c.text.write = snd_pcm_lib_preallocate_proc_write;
	entry->mode \|= S_IWUSR;
	entry->private_data = substream;
	if (snd_info_register(entry) < 0) {
	snd_info_free_entry(entry);
	entry = NULL;
	}
	}
	substream->proc_prealloc_entry = entry;
	if ((entry = snd_info_create_card_entry(substream->pcm->card, "prealloc_max", substream->proc_root)) != NULL) {
	entry->c.text.read = snd_pcm_lib_preallocate_max_proc_read;
	entry->private_data = substream;
	if (snd_info_register(entry) < 0) {
	snd_info_free_entry(entry);
	entry = NULL;
	}
	}
	substream->proc_prealloc_max_entry = entry;
	}

	#else /* !CONFIG_SND_VERBOSE_PROCFS */
	#define preallocate_info_init(s)
	#endif /* CONFIG_SND_VERBOSE_PROCFS */

	/*
	* pre-allocate the buffer and create a proc file for the substream
	*/
	static int snd_pcm_lib_preallocate_pages1(struct snd_pcm_substream *substream,
	size_t size, size_t max)
	{

	if (size > 0 && preallocate_dma && substream->number < maximum_substreams)
	preallocate_pcm_pages(substream, size);

	if (substream->dma_buffer.bytes > 0)
	substream->buffer_bytes_max = substream->dma_buffer.bytes;
	substream->dma_max = max;
	preallocate_info_init(substream);
	return 0;
	}


	/**
	* snd_pcm_lib_preallocate_pages - pre-allocation for the given DMA type
	* @substream: the pcm substream instance
	* @type: DMA type (SNDRV_DMA_TYPE_*)
	* @data: DMA type dependant data
	* @size: the requested pre-allocation size in bytes
	* @max: the max. allowed pre-allocation size
	*
	* Do pre-allocation for the given DMA buffer type.
	*
	* When substream->dma_buf_id is set, the function tries to look for
	* the reserved buffer, and the buffer is not freed but reserved at
	* destruction time. The dma_buf_id must be unique for all systems
	* (in the same DMA buffer type) e.g. using snd_dma_pci_buf_id().
	*
	* Returns zero if successful, or a negative error code on failure.
	*/
	int snd_pcm_lib_preallocate_pages(struct snd_pcm_substream *substream,
	int type, struct device *data,
	size_t size, size_t max)
	{
	substream->dma_buffer.dev.type = type;
	substream->dma_buffer.dev.dev = data;
	return snd_pcm_lib_preallocate_pages1(substream, size, max);
	}

	EXPORT_SYMBOL(snd_pcm_lib_preallocate_pages);

	/**
	* snd_pcm_lib_preallocate_pages_for_all - pre-allocation for continous memory type (all substreams)
	* @pcm: the pcm instance
	* @type: DMA type (SNDRV_DMA_TYPE_*)
	* @data: DMA type dependant data
	* @size: the requested pre-allocation size in bytes
	* @max: the max. allowed pre-allocation size
	*
	* Do pre-allocation to all substreams of the given pcm for the
	* specified DMA type.
	*
	* Returns zero if successful, or a negative error code on failure.
	*/
	int snd_pcm_lib_preallocate_pages_for_all(struct snd_pcm *pcm,
	int type, void *data,
	size_t size, size_t max)
	{
	struct snd_pcm_substream *substream;
	int stream, err;

	for (stream = 0; stream < 2; stream++)
	for (substream = pcm->streams[stream].substream; substream; substream = substream->next)
	if ((err = snd_pcm_lib_preallocate_pages(substream, type, data, size, max)) < 0)
	return err;
	return 0;
	}

	EXPORT_SYMBOL(snd_pcm_lib_preallocate_pages_for_all);

	/**
	* snd_pcm_sgbuf_ops_page - get the page struct at the given offset
	* @substream: the pcm substream instance
	* @offset: the buffer offset
	*
	* Returns the page struct at the given buffer offset.
	* Used as the page callback of PCM ops.
	*/
	struct page snd_pcm_sgbuf_ops_page(struct snd_pcm_substream substream, unsigned long offset)
	{
	struct snd_sg_buf *sgbuf = snd_pcm_substream_sgbuf(substream);

	unsigned int idx = offset >> PAGE_SHIFT;
	if (idx >= (unsigned int)sgbuf->pages)
	return NULL;
	return sgbuf->page_table[idx];
	}

	EXPORT_SYMBOL(snd_pcm_sgbuf_ops_page);

	/*
	* compute the max chunk size with continuous pages on sg-buffer
	*/
	unsigned int snd_pcm_sgbuf_get_chunk_size(struct snd_pcm_substream *substream,
	unsigned int ofs, unsigned int size)
	{
	struct snd_sg_buf *sg = snd_pcm_substream_sgbuf(substream);
	unsigned int start, end, pg;

	start = ofs >> PAGE_SHIFT;
	end = (ofs + size - 1) >> PAGE_SHIFT;
	/* check page continuity */
	pg = sg->table[start].addr >> PAGE_SHIFT;
	for (;;) {
	start++;
	if (start > end)
	break;
	pg++;
	if ((sg->table[start].addr >> PAGE_SHIFT) != pg)
	return (start << PAGE_SHIFT) - ofs;
	}
	/* ok, all on continuous pages */
	return size;
	}
	EXPORT_SYMBOL(snd_pcm_sgbuf_get_chunk_size);

	/**
	* snd_pcm_lib_malloc_pages - allocate the DMA buffer
	* @substream: the substream to allocate the DMA buffer to
	* @size: the requested buffer size in bytes
	*
	* Allocates the DMA buffer on the BUS type given earlier to
	* snd_pcm_lib_preallocate_xxx_pages().
	*
	* Returns 1 if the buffer is changed, 0 if not changed, or a negative
	* code on failure.
	*/
	int snd_pcm_lib_malloc_pages(struct snd_pcm_substream *substream, size_t size)
	{
	struct snd_pcm_runtime *runtime;
	struct snd_dma_buffer *dmab = NULL;

	if (PCM_RUNTIME_CHECK(substream))
	return -EINVAL;
	if (snd_BUG_ON(substream->dma_buffer.dev.type ==
	SNDRV_DMA_TYPE_UNKNOWN))
	return -EINVAL;
	runtime = substream->runtime;

	if (runtime->dma_buffer_p) {
	/* perphaps, we might free the large DMA memory region
	to save some space here, but the actual solution
	costs us less time */
	if (runtime->dma_buffer_p->bytes >= size) {
	runtime->dma_bytes = size;
	return 0; /* ok, do not change */
	}
	snd_pcm_lib_free_pages(substream);
	}
	if (substream->dma_buffer.area != NULL &&
	substream->dma_buffer.bytes >= size) {
	dmab = &substream->dma_buffer; /* use the pre-allocated buffer */
	} else {
	dmab = kzalloc(sizeof(*dmab), GFP_KERNEL);
	if (! dmab)
	return -ENOMEM;
	dmab->dev = substream->dma_buffer.dev;
	if (snd_dma_alloc_pages(substream->dma_buffer.dev.type,
	substream->dma_buffer.dev.dev,
	size, dmab) < 0) {
	kfree(dmab);
	return -ENOMEM;
	}
	}
	snd_pcm_set_runtime_buffer(substream, dmab);
	runtime->dma_bytes = size;
	return 1; /* area was changed */
	}

	EXPORT_SYMBOL(snd_pcm_lib_malloc_pages);

	/**
	* snd_pcm_lib_free_pages - release the allocated DMA buffer.
	* @substream: the substream to release the DMA buffer
	*
	* Releases the DMA buffer allocated via snd_pcm_lib_malloc_pages().
	*
	* Returns zero if successful, or a negative error code on failure.
	*/
	int snd_pcm_lib_free_pages(struct snd_pcm_substream *substream)
	{
	struct snd_pcm_runtime *runtime;

	if (PCM_RUNTIME_CHECK(substream))
	return -EINVAL;
	runtime = substream->runtime;
	if (runtime->dma_area == NULL)
	return 0;
	if (runtime->dma_buffer_p != &substream->dma_buffer) {
	/* it's a newly allocated buffer. release it now. */
	snd_dma_free_pages(runtime->dma_buffer_p);
	kfree(runtime->dma_buffer_p);
	}
	snd_pcm_set_runtime_buffer(substream, NULL);
	return 0;
	}

	EXPORT_SYMBOL(snd_pcm_lib_free_pages);