drivers/media/video/videobuf-msm-mem.c - kernel/msm - Gitiles

 /* Copyright (c) 2011, The Linux Foundation. All rights reserved.
  *
  * Based on videobuf-dma-contig.c,
  * (c) 2008 Magnus Damm
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 and
  * only version 2 as published by the Free Software Foundation.
  *
  * 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.
  *
  * helper functions for physically contiguous pmem capture buffers
  * The functions support contiguous memory allocations using pmem
  * kernel API.
  */

 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/pagemap.h>
 #include <linux/sched.h>
 #include <linux/io.h>
 #include <linux/android_pmem.h>
 #include <linux/memory_alloc.h>
 #include <media/videobuf-msm-mem.h>
 #include <media/msm_camera.h>
 #include <mach/memory.h>

 #define MAGIC_PMEM 0x0733ac64
 #define MAGIC_CHECK(is, should)               \
 	if (unlikely((is) != (should))) {           \
 		pr_err("magic mismatch: %x expected %x\n", (is), (should)); \
 		BUG();                  \
 	}

 #ifdef CONFIG_MSM_CAMERA_DEBUG
 #define D(fmt, args...) printk(KERN_DEBUG "videobuf-msm-mem: " fmt, ##args)
 #else
 #define D(fmt, args...) do {} while (0)
 #endif

 static int32_t msm_mem_allocate(const size_t size)
 {
 	int32_t phyaddr;
 	phyaddr = allocate_contiguous_ebi_nomap(size, SZ_4K);
 	return phyaddr;
 }

 static int32_t msm_mem_free(const int32_t phyaddr)
 {
 	int32_t rc = 0;
 	free_contiguous_memory_by_paddr(phyaddr);
 	return rc;
 }

 static void
 videobuf_vm_open(struct vm_area_struct *vma)
 {
 	struct videobuf_mapping *map = vma->vm_private_data;

 	D("vm_open %p [count=%u,vma=%08lx-%08lx]\n",
 		map, map->count, vma->vm_start, vma->vm_end);

 	map->count++;
 }

 static void videobuf_vm_close(struct vm_area_struct *vma)
 {
 	struct videobuf_mapping *map = vma->vm_private_data;
 	struct videobuf_queue *q = map->q;
 	int i, rc;

 	D("vm_close %p [count=%u,vma=%08lx-%08lx]\n",
 		map, map->count, vma->vm_start, vma->vm_end);

 	map->count--;
 	if (0 == map->count) {
 		struct videobuf_contig_pmem *mem;

 		D("munmap %p q=%p\n", map, q);
 		mutex_lock(&q->vb_lock);

 		/* We need first to cancel streams, before unmapping */
 		if (q->streaming)
 			videobuf_queue_cancel(q);

 		for (i = 0; i < VIDEO_MAX_FRAME; i++) {
 			if (NULL == q->bufs[i])
 				continue;

 			if (q->bufs[i]->map != map)
 				continue;

 			mem = q->bufs[i]->priv;
 			if (mem) {
 				/* This callback is called only if kernel has
 				 * allocated memory and this memory is mmapped.
 				 * In this case, memory should be freed,
 				 * in order to do memory unmap.
 				 */

 				MAGIC_CHECK(mem->magic, MAGIC_PMEM);

 				/* vfree is not atomic - can't be
 				 called with IRQ's disabled
 				 */
 				D("buf[%d] freeing physical %d\n",
 					i, mem->phyaddr);

 				rc = msm_mem_free(mem->phyaddr);
 				if (rc < 0)
 					D("%s: Invalid memory location\n",
 								__func__);
 				else {
 					mem->phyaddr = 0;
 				}
 			}

 			q->bufs[i]->map   = NULL;
 			q->bufs[i]->baddr = 0;
 		}

 		kfree(map);

 		mutex_unlock(&q->vb_lock);

 		/* deallocate the q->bufs[i] structure not a good solution
 		 as it will result in unnecessary iterations but right now
 		 this looks like the only cleaner way  */
 		videobuf_mmap_free(q);
 	}
 }

 static const struct vm_operations_struct videobuf_vm_ops = {
 	.open     = videobuf_vm_open,
 	.close    = videobuf_vm_close,
 };

 /**
  * videobuf_pmem_contig_user_put() - reset pointer to user space buffer
  * @mem: per-buffer private videobuf-contig-pmem data
  *
  * This function resets the user space pointer
  */
 static void videobuf_pmem_contig_user_put(struct videobuf_contig_pmem *mem)
 {
 	if (mem->phyaddr) {
 		put_pmem_file(mem->file);
 		mem->is_userptr = 0;
 		mem->phyaddr = 0;
 		mem->size = 0;
 	}
 }

 /**
  * videobuf_pmem_contig_user_get() - setup user space memory pointer
  * @mem: per-buffer private videobuf-contig-pmem data
  * @vb: video buffer to map
  *
  * This function validates and sets up a pointer to user space memory.
  * Only physically contiguous pfn-mapped memory is accepted.
  *
  * Returns 0 if successful.
  */
 static int videobuf_pmem_contig_user_get(struct videobuf_contig_pmem *mem,
 					struct videobuf_buffer *vb)
 {
 	unsigned long kvstart;
 	unsigned long len;
 	int rc;

 	mem->size = PAGE_ALIGN(vb->size);
 	rc = get_pmem_file(vb->baddr, (unsigned long *)&mem->phyaddr,
 					&kvstart, &len, &mem->file);
 	if (rc < 0) {
 		pr_err("%s: get_pmem_file fd %lu error %d\n",
 					__func__, vb->baddr,
 							rc);
 		return rc;
 	}
 	mem->phyaddr += vb->boff;
 	mem->y_off = 0;
 	mem->cbcr_off = (vb->size)*2/3;
 	mem->is_userptr = 1;
 	return rc;
 }

 static struct videobuf_buffer *__videobuf_alloc(size_t size)
 {
 	struct videobuf_contig_pmem *mem;
 	struct videobuf_buffer *vb;

 	vb = kzalloc(size + sizeof(*mem), GFP_KERNEL);
 	if (vb) {
 		mem = vb->priv = ((char *)vb) + size;
 		mem->magic = MAGIC_PMEM;
 	}

 	return vb;
 }

 static void *__videobuf_to_vaddr(struct videobuf_buffer *buf)
 {
 	struct videobuf_contig_pmem *mem = buf->priv;

 	BUG_ON(!mem);
 	MAGIC_CHECK(mem->magic, MAGIC_PMEM);

 	return mem->vaddr;
 }

 static int __videobuf_iolock(struct videobuf_queue *q,
 				struct videobuf_buffer *vb,
 				struct v4l2_framebuffer *fbuf)
 {
 	int rc = 0;
 	struct videobuf_contig_pmem *mem = vb->priv;

 	BUG_ON(!mem);
 	MAGIC_CHECK(mem->magic, MAGIC_PMEM);

 	switch (vb->memory) {
 	case V4L2_MEMORY_MMAP:
 		D("%s memory method MMAP\n", __func__);

 		/* All handling should be done by __videobuf_mmap_mapper() */
 		break;
 	case V4L2_MEMORY_USERPTR:
 		D("%s memory method USERPTR\n", __func__);

 		/* handle pointer from user space */
 		rc = videobuf_pmem_contig_user_get(mem, vb);
 		break;
 	case V4L2_MEMORY_OVERLAY:
 	default:
 		pr_err("%s memory method OVERLAY/unknown\n", __func__);
 		rc = -EINVAL;
 	}

 	return rc;
 }

 static int __videobuf_mmap_mapper(struct videobuf_queue *q,
 		struct videobuf_buffer *buf,
 		struct vm_area_struct *vma)
 {
 	struct videobuf_contig_pmem *mem;
 	struct videobuf_mapping *map;
 	int retval;
 	unsigned long size;

 	D("%s\n", __func__);

 	/* create mapping + update buffer list */
 	map = kzalloc(sizeof(struct videobuf_mapping), GFP_KERNEL);
 	if (!map) {
 		pr_err("%s: kzalloc failed.\n", __func__);
 		return -ENOMEM;
 	}

 	buf->map = map;
 	map->q = q;

 	buf->baddr = vma->vm_start;

 	mem = buf->priv;
 	D("mem = 0x%x\n", (u32)mem);
 	D("buf = 0x%x\n", (u32)buf);
 	BUG_ON(!mem);
 	MAGIC_CHECK(mem->magic, MAGIC_PMEM);

 	mem->size = PAGE_ALIGN(buf->bsize);
 	mem->y_off = 0;
 	mem->cbcr_off = (buf->bsize)*2/3;
 	if (buf->i >= 0 && buf->i <= 3)
 		mem->buffer_type = OUTPUT_TYPE_P;
 	else
 		mem->buffer_type = OUTPUT_TYPE_V;

 	buf->bsize = mem->size;
 	mem->phyaddr = msm_mem_allocate(mem->size);

 	if (!mem->phyaddr) {
 		pr_err("%s : pmem memory allocation failed\n", __func__);
 		goto error;
 	}

 	/* Try to remap memory */
 	size = vma->vm_end - vma->vm_start;
 	size = (size < mem->size) ? size : mem->size;

 	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 	retval = remap_pfn_range(vma, vma->vm_start,
 		mem->phyaddr >> PAGE_SHIFT,
 		size, vma->vm_page_prot);
 	if (retval) {
 		pr_err("mmap: remap failed with error %d. ", retval);
 		retval = msm_mem_free(mem->phyaddr);
 		if (retval < 0)
 			printk(KERN_ERR "%s: Invalid memory location\n",
 								__func__);
 		else {
 			mem->phyaddr = 0;
 		}
 		goto error;
 	}

 	vma->vm_ops          = &videobuf_vm_ops;
 	vma->vm_flags       |= VM_DONTEXPAND;
 	vma->vm_private_data = map;

 	D("mmap %p: q=%p %08lx-%08lx (%lx) pgoff %08lx buf %d\n",
 		map, q, vma->vm_start, vma->vm_end,
 		(long int)buf->bsize,
 		vma->vm_pgoff, buf->i);

 	videobuf_vm_open(vma);

 	return 0;

 error:
 	kfree(map);
 	return -ENOMEM;
 }

 static struct videobuf_qtype_ops qops = {
 	.magic        = MAGIC_QTYPE_OPS,

 	.alloc_vb     = __videobuf_alloc,
 	.iolock       = __videobuf_iolock,
 	.mmap_mapper  = __videobuf_mmap_mapper,
 	.vaddr        = __videobuf_to_vaddr,
 };

 void videobuf_queue_pmem_contig_init(struct videobuf_queue *q,
 	const struct videobuf_queue_ops *ops,
 	struct device *dev,
 	spinlock_t *irqlock,
 	enum v4l2_buf_type type,
 	enum v4l2_field field,
 	unsigned int msize,
 	void *priv,
 	struct mutex *ext_lock)
 {
 	videobuf_queue_core_init(q, ops, dev, irqlock, type, field, msize,
 							priv, &qops, ext_lock);
 }
 EXPORT_SYMBOL_GPL(videobuf_queue_pmem_contig_init);

 int videobuf_to_pmem_contig(struct videobuf_buffer *buf)
 {
 	struct videobuf_contig_pmem *mem = buf->priv;

 	BUG_ON(!mem);
 	MAGIC_CHECK(mem->magic, MAGIC_PMEM);

 	return mem->phyaddr;
 }
 EXPORT_SYMBOL_GPL(videobuf_to_pmem_contig);

 int videobuf_pmem_contig_free(struct videobuf_queue *q,
 				struct videobuf_buffer *buf)
 {
 	struct videobuf_contig_pmem *mem = buf->priv;

 	/* mmapped memory can't be freed here, otherwise mmapped region
 	 would be released, while still needed. In this case, the memory
 	 release should happen inside videobuf_vm_close().
 	 So, it should free memory only if the memory were allocated for
 	 read() operation.
 	*/
 	if (buf->memory != V4L2_MEMORY_USERPTR)
 		return -EINVAL;

 	if (!mem)
 		return -ENOMEM;

 	MAGIC_CHECK(mem->magic, MAGIC_PMEM);

 	/* handle user space pointer case */
 	if (buf->baddr) {
 		videobuf_pmem_contig_user_put(mem);
 		return 0;
 	} else {
 		/* don't support read() method */
 		return -EINVAL;
 	}
 }
 EXPORT_SYMBOL_GPL(videobuf_pmem_contig_free);

 MODULE_DESCRIPTION("helper module to manage video4linux PMEM contig buffers");
 MODULE_LICENSE("GPL v2");
	/* Copyright (c) 2011, The Linux Foundation. All rights reserved.
	*
	* Based on videobuf-dma-contig.c,
	* (c) 2008 Magnus Damm
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 and
	* only version 2 as published by the Free Software Foundation.
	*
	* 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.
	*
	* helper functions for physically contiguous pmem capture buffers
	* The functions support contiguous memory allocations using pmem
	* kernel API.
	*/

	#include <linux/init.h>
	#include <linux/module.h>
	#include <linux/mm.h>
	#include <linux/slab.h>
	#include <linux/pagemap.h>
	#include <linux/sched.h>
	#include <linux/io.h>
	#include <linux/android_pmem.h>
	#include <linux/memory_alloc.h>
	#include <media/videobuf-msm-mem.h>
	#include <media/msm_camera.h>
	#include <mach/memory.h>

	#define MAGIC_PMEM 0x0733ac64
	#define MAGIC_CHECK(is, should) \
	if (unlikely((is) != (should))) { \
	pr_err("magic mismatch: %x expected %x\n", (is), (should)); \
	BUG(); \
	}

	#ifdef CONFIG_MSM_CAMERA_DEBUG
	#define D(fmt, args...) printk(KERN_DEBUG "videobuf-msm-mem: " fmt, ##args)
	#else
	#define D(fmt, args...) do {} while (0)
	#endif

	static int32_t msm_mem_allocate(const size_t size)
	{
	int32_t phyaddr;
	phyaddr = allocate_contiguous_ebi_nomap(size, SZ_4K);
	return phyaddr;
	}

	static int32_t msm_mem_free(const int32_t phyaddr)
	{
	int32_t rc = 0;
	free_contiguous_memory_by_paddr(phyaddr);
	return rc;
	}

	static void
	videobuf_vm_open(struct vm_area_struct *vma)
	{
	struct videobuf_mapping *map = vma->vm_private_data;

	D("vm_open %p [count=%u,vma=%08lx-%08lx]\n",
	map, map->count, vma->vm_start, vma->vm_end);

	map->count++;
	}

	static void videobuf_vm_close(struct vm_area_struct *vma)
	{
	struct videobuf_mapping *map = vma->vm_private_data;
	struct videobuf_queue *q = map->q;
	int i, rc;

	D("vm_close %p [count=%u,vma=%08lx-%08lx]\n",
	map, map->count, vma->vm_start, vma->vm_end);

	map->count--;
	if (0 == map->count) {
	struct videobuf_contig_pmem *mem;

	D("munmap %p q=%p\n", map, q);
	mutex_lock(&q->vb_lock);

	/* We need first to cancel streams, before unmapping */
	if (q->streaming)
	videobuf_queue_cancel(q);

	for (i = 0; i < VIDEO_MAX_FRAME; i++) {
	if (NULL == q->bufs[i])
	continue;

	if (q->bufs[i]->map != map)
	continue;

	mem = q->bufs[i]->priv;
	if (mem) {
	/* This callback is called only if kernel has
	* allocated memory and this memory is mmapped.
	* In this case, memory should be freed,
	* in order to do memory unmap.
	*/

	MAGIC_CHECK(mem->magic, MAGIC_PMEM);

	/* vfree is not atomic - can't be
	called with IRQ's disabled
	*/
	D("buf[%d] freeing physical %d\n",
	i, mem->phyaddr);

	rc = msm_mem_free(mem->phyaddr);
	if (rc < 0)
	D("%s: Invalid memory location\n",
	__func__);
	else {
	mem->phyaddr = 0;
	}
	}

	q->bufs[i]->map = NULL;
	q->bufs[i]->baddr = 0;
	}

	kfree(map);

	mutex_unlock(&q->vb_lock);

	/* deallocate the q->bufs[i] structure not a good solution
	as it will result in unnecessary iterations but right now
	this looks like the only cleaner way */
	videobuf_mmap_free(q);
	}
	}

	static const struct vm_operations_struct videobuf_vm_ops = {
	.open = videobuf_vm_open,
	.close = videobuf_vm_close,
	};

	/**
	* videobuf_pmem_contig_user_put() - reset pointer to user space buffer
	* @mem: per-buffer private videobuf-contig-pmem data
	*
	* This function resets the user space pointer
	*/
	static void videobuf_pmem_contig_user_put(struct videobuf_contig_pmem *mem)
	{
	if (mem->phyaddr) {
	put_pmem_file(mem->file);
	mem->is_userptr = 0;
	mem->phyaddr = 0;
	mem->size = 0;
	}
	}

	/**
	* videobuf_pmem_contig_user_get() - setup user space memory pointer
	* @mem: per-buffer private videobuf-contig-pmem data
	* @vb: video buffer to map
	*
	* This function validates and sets up a pointer to user space memory.
	* Only physically contiguous pfn-mapped memory is accepted.
	*
	* Returns 0 if successful.
	*/
	static int videobuf_pmem_contig_user_get(struct videobuf_contig_pmem *mem,
	struct videobuf_buffer *vb)
	{
	unsigned long kvstart;
	unsigned long len;
	int rc;

	mem->size = PAGE_ALIGN(vb->size);
	rc = get_pmem_file(vb->baddr, (unsigned long *)&mem->phyaddr,
	&kvstart, &len, &mem->file);
	if (rc < 0) {
	pr_err("%s: get_pmem_file fd %lu error %d\n",
	__func__, vb->baddr,
	rc);
	return rc;
	}
	mem->phyaddr += vb->boff;
	mem->y_off = 0;
	mem->cbcr_off = (vb->size)*2/3;
	mem->is_userptr = 1;
	return rc;
	}

	static struct videobuf_buffer *__videobuf_alloc(size_t size)
	{
	struct videobuf_contig_pmem *mem;
	struct videobuf_buffer *vb;

	vb = kzalloc(size + sizeof(*mem), GFP_KERNEL);
	if (vb) {
	mem = vb->priv = ((char *)vb) + size;
	mem->magic = MAGIC_PMEM;
	}

	return vb;
	}

	static void __videobuf_to_vaddr(struct videobuf_buffer buf)
	{
	struct videobuf_contig_pmem *mem = buf->priv;

	BUG_ON(!mem);
	MAGIC_CHECK(mem->magic, MAGIC_PMEM);

	return mem->vaddr;
	}

	static int __videobuf_iolock(struct videobuf_queue *q,
	struct videobuf_buffer *vb,
	struct v4l2_framebuffer *fbuf)
	{
	int rc = 0;
	struct videobuf_contig_pmem *mem = vb->priv;

	BUG_ON(!mem);
	MAGIC_CHECK(mem->magic, MAGIC_PMEM);

	switch (vb->memory) {
	case V4L2_MEMORY_MMAP:
	D("%s memory method MMAP\n", __func__);

	/* All handling should be done by __videobuf_mmap_mapper() */
	break;
	case V4L2_MEMORY_USERPTR:
	D("%s memory method USERPTR\n", __func__);

	/* handle pointer from user space */
	rc = videobuf_pmem_contig_user_get(mem, vb);
	break;
	case V4L2_MEMORY_OVERLAY:
	default:
	pr_err("%s memory method OVERLAY/unknown\n", __func__);
	rc = -EINVAL;
	}

	return rc;
	}

	static int __videobuf_mmap_mapper(struct videobuf_queue *q,
	struct videobuf_buffer *buf,
	struct vm_area_struct *vma)
	{
	struct videobuf_contig_pmem *mem;
	struct videobuf_mapping *map;
	int retval;
	unsigned long size;

	D("%s\n", __func__);

	/* create mapping + update buffer list */
	map = kzalloc(sizeof(struct videobuf_mapping), GFP_KERNEL);
	if (!map) {
	pr_err("%s: kzalloc failed.\n", __func__);
	return -ENOMEM;
	}

	buf->map = map;
	map->q = q;

	buf->baddr = vma->vm_start;

	mem = buf->priv;
	D("mem = 0x%x\n", (u32)mem);
	D("buf = 0x%x\n", (u32)buf);
	BUG_ON(!mem);
	MAGIC_CHECK(mem->magic, MAGIC_PMEM);

	mem->size = PAGE_ALIGN(buf->bsize);
	mem->y_off = 0;
	mem->cbcr_off = (buf->bsize)*2/3;
	if (buf->i >= 0 && buf->i <= 3)
	mem->buffer_type = OUTPUT_TYPE_P;
	else
	mem->buffer_type = OUTPUT_TYPE_V;

	buf->bsize = mem->size;
	mem->phyaddr = msm_mem_allocate(mem->size);

	if (!mem->phyaddr) {
	pr_err("%s : pmem memory allocation failed\n", __func__);
	goto error;
	}

	/* Try to remap memory */
	size = vma->vm_end - vma->vm_start;
	size = (size < mem->size) ? size : mem->size;

	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
	retval = remap_pfn_range(vma, vma->vm_start,
	mem->phyaddr >> PAGE_SHIFT,
	size, vma->vm_page_prot);
	if (retval) {
	pr_err("mmap: remap failed with error %d. ", retval);
	retval = msm_mem_free(mem->phyaddr);
	if (retval < 0)
	printk(KERN_ERR "%s: Invalid memory location\n",
	__func__);
	else {
	mem->phyaddr = 0;
	}
	goto error;
	}

	vma->vm_ops = &videobuf_vm_ops;
	vma->vm_flags \|= VM_DONTEXPAND;
	vma->vm_private_data = map;

	D("mmap %p: q=%p %08lx-%08lx (%lx) pgoff %08lx buf %d\n",
	map, q, vma->vm_start, vma->vm_end,
	(long int)buf->bsize,
	vma->vm_pgoff, buf->i);

	videobuf_vm_open(vma);

	return 0;

	error:
	kfree(map);
	return -ENOMEM;
	}

	static struct videobuf_qtype_ops qops = {
	.magic = MAGIC_QTYPE_OPS,

	.alloc_vb = __videobuf_alloc,
	.iolock = __videobuf_iolock,
	.mmap_mapper = __videobuf_mmap_mapper,
	.vaddr = __videobuf_to_vaddr,
	};

	void videobuf_queue_pmem_contig_init(struct videobuf_queue *q,
	const struct videobuf_queue_ops *ops,
	struct device *dev,
	spinlock_t *irqlock,
	enum v4l2_buf_type type,
	enum v4l2_field field,
	unsigned int msize,
	void *priv,
	struct mutex *ext_lock)
	{
	videobuf_queue_core_init(q, ops, dev, irqlock, type, field, msize,
	priv, &qops, ext_lock);
	}
	EXPORT_SYMBOL_GPL(videobuf_queue_pmem_contig_init);

	int videobuf_to_pmem_contig(struct videobuf_buffer *buf)
	{
	struct videobuf_contig_pmem *mem = buf->priv;

	BUG_ON(!mem);
	MAGIC_CHECK(mem->magic, MAGIC_PMEM);

	return mem->phyaddr;
	}
	EXPORT_SYMBOL_GPL(videobuf_to_pmem_contig);

	int videobuf_pmem_contig_free(struct videobuf_queue *q,
	struct videobuf_buffer *buf)
	{
	struct videobuf_contig_pmem *mem = buf->priv;

	/* mmapped memory can't be freed here, otherwise mmapped region
	would be released, while still needed. In this case, the memory
	release should happen inside videobuf_vm_close().
	So, it should free memory only if the memory were allocated for
	read() operation.
	*/
	if (buf->memory != V4L2_MEMORY_USERPTR)
	return -EINVAL;

	if (!mem)
	return -ENOMEM;

	MAGIC_CHECK(mem->magic, MAGIC_PMEM);

	/* handle user space pointer case */
	if (buf->baddr) {
	videobuf_pmem_contig_user_put(mem);
	return 0;
	} else {
	/* don't support read() method */
	return -EINVAL;
	}
	}
	EXPORT_SYMBOL_GPL(videobuf_pmem_contig_free);

	MODULE_DESCRIPTION("helper module to manage video4linux PMEM contig buffers");
	MODULE_LICENSE("GPL v2");