drivers/media/v4l2-core/videobuf2-memops.c

/*
 * videobuf2-memops.c - generic memory handling routines for videobuf2
 *
 * Copyright (C) 2010 Samsung Electronics
 *
 * Author: Pawel Osciak <pawel@osciak.com>
 *	   Marek Szyprowski <m.szyprowski@samsung.com>
 *
 * 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.
 */

#include <linux/slab.h>
#include <linux/module.h>
#include <linux/dma-mapping.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/file.h>

#include <media/videobuf2-core.h>
#include <media/videobuf2-memops.h>

/**
 * vb2_get_vma() - acquire and lock the virtual memory area
 * @vma:	given virtual memory area
 *
 * This function attempts to acquire an area mapped in the userspace for
 * the duration of a hardware operation. The area is "locked" by performing
 * the same set of operation that are done when process calls fork() and
 * memory areas are duplicated.
 *
 * Returns a copy of a virtual memory region on success or NULL.
 */
struct vm_area_struct *vb2_get_vma(struct vm_area_struct *vma)
{
	struct vm_area_struct *vma_copy;

	vma_copy = kmalloc(sizeof(*vma_copy), GFP_KERNEL);
	if (vma_copy == NULL)
		return NULL;

	if (vma->vm_ops && vma->vm_ops->open)
		vma->vm_ops->open(vma);

	if (vma->vm_file)
		get_file(vma->vm_file);

	memcpy(vma_copy, vma, sizeof(*vma));

	vma_copy->vm_mm = NULL;
	vma_copy->vm_next = NULL;
	vma_copy->vm_prev = NULL;

	return vma_copy;
}
EXPORT_SYMBOL_GPL(vb2_get_vma);

/**
 * vb2_put_userptr() - release a userspace virtual memory area
 * @vma:	virtual memory region associated with the area to be released
 *
 * This function releases the previously acquired memory area after a hardware
 * operation.
 */
void vb2_put_vma(struct vm_area_struct *vma)
{
	if (!vma)
		return;

	if (vma->vm_ops && vma->vm_ops->close)
		vma->vm_ops->close(vma);

	if (vma->vm_file)
		fput(vma->vm_file);

	kfree(vma);
}
EXPORT_SYMBOL_GPL(vb2_put_vma);

/**
 * vb2_get_contig_userptr() - lock physically contiguous userspace mapped memory
 * @vaddr:	starting virtual address of the area to be verified
 * @size:	size of the area
 * @res_paddr:	will return physical address for the given vaddr
 * @res_vma:	will return locked copy of struct vm_area for the given area
 *
 * This function will go through memory area of size @size mapped at @vaddr and
 * verify that the underlying physical pages are contiguous. If they are
 * contiguous the virtual memory area is locked and a @res_vma is filled with
 * the copy and @res_pa set to the physical address of the buffer.
 *
 * Returns 0 on success.
 */
int vb2_get_contig_userptr(unsigned long vaddr, unsigned long size,
			   struct vm_area_struct **res_vma, dma_addr_t *res_pa)
{
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;
	unsigned long offset, start, end;
	unsigned long this_pfn, prev_pfn;
	dma_addr_t pa = 0;

	start = vaddr;
	offset = start & ~PAGE_MASK;
	end = start + size;

	vma = find_vma(mm, start);

	if (vma == NULL || vma->vm_end < end)
		return -EFAULT;

	for (prev_pfn = 0; start < end; start += PAGE_SIZE) {
		int ret = follow_pfn(vma, start, &this_pfn);
		if (ret)
			return ret;

		if (prev_pfn == 0)
			pa = this_pfn << PAGE_SHIFT;
		else if (this_pfn != prev_pfn + 1)
			return -EFAULT;

		prev_pfn = this_pfn;
	}

	/*
	 * Memory is contigous, lock vma and return to the caller
	 */
	*res_vma = vb2_get_vma(vma);
	if (*res_vma == NULL)
		return -ENOMEM;

	*res_pa = pa + offset;
	return 0;
}
EXPORT_SYMBOL_GPL(vb2_get_contig_userptr);

/**
 * vb2_common_vm_open() - increase refcount of the vma
 * @vma:	virtual memory region for the mapping
 *
 * This function adds another user to the provided vma. It expects
 * struct vb2_vmarea_handler pointer in vma->vm_private_data.
 */
static void vb2_common_vm_open(struct vm_area_struct *vma)
{
	struct vb2_vmarea_handler *h = vma->vm_private_data;

	pr_debug("%s: %p, refcount: %d, vma: %08lx-%08lx\n",
	       __func__, h, atomic_read(h->refcount), vma->vm_start,
	       vma->vm_end);

	atomic_inc(h->refcount);
}

/**
 * vb2_common_vm_close() - decrease refcount of the vma
 * @vma:	virtual memory region for the mapping
 *
 * This function releases the user from the provided vma. It expects
 * struct vb2_vmarea_handler pointer in vma->vm_private_data.
 */
static void vb2_common_vm_close(struct vm_area_struct *vma)
{
	struct vb2_vmarea_handler *h = vma->vm_private_data;

	pr_debug("%s: %p, refcount: %d, vma: %08lx-%08lx\n",
	       __func__, h, atomic_read(h->refcount), vma->vm_start,
	       vma->vm_end);

	h->put(h->arg);
}

/**
 * vb2_common_vm_ops - common vm_ops used for tracking refcount of mmaped
 * video buffers
 */
const struct vm_operations_struct vb2_common_vm_ops = {
	.open = vb2_common_vm_open,
	.close = vb2_common_vm_close,
};
EXPORT_SYMBOL_GPL(vb2_common_vm_ops);

MODULE_DESCRIPTION("common memory handling routines for videobuf2");
MODULE_AUTHOR("Pawel Osciak <pawel@osciak.com>");
MODULE_LICENSE("GPL");