[media] v4l: videobuf2: add generic memory handling routines

Add generic memory handling routines for userspace pointer handling,
contiguous memory verification and mapping.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Pawel Osciak <p.osciak@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
CC: Pawel Osciak <pawel@osciak.com>
Reviewed-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 232 insertions, 0 deletions

diff --git a/drivers/media/video/videobuf2-memops.c b/drivers/media/video/videobuf2-memops.c
new file mode 100644
index 000000000000..053c15794b8d
--- /dev/null
+++ b/drivers/media/video/videobuf2-memops.c
@@ -0,0 +1,232 @@
+/*
+ * videobuf2-memops.c - generic memory handling routines for videobuf2
+ *
+ * Copyright (C) 2010 Samsung Electronics
+ *
+ * Author: Pawel Osciak <p.osciak@samsung.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 <linux/slab.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;
+}
+
+/**
+ * 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_file)
+		fput(vma->vm_file);
+
+	if (vma->vm_ops && vma->vm_ops->close)
+		vma->vm_ops->close(vma);
+
+	kfree(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;
+	int ret = -EFAULT;
+
+	start = vaddr;
+	offset = start & ~PAGE_MASK;
+	end = start + size;
+
+	down_read(&mm->mmap_sem);
+	vma = find_vma(mm, start);
+
+	if (vma == NULL || vma->vm_end < end)
+		goto done;
+
+	for (prev_pfn = 0; start < end; start += PAGE_SIZE) {
+		ret = follow_pfn(vma, start, &this_pfn);
+		if (ret)
+			goto done;
+
+		if (prev_pfn == 0)
+			pa = this_pfn << PAGE_SHIFT;
+		else if (this_pfn != prev_pfn + 1) {
+			ret = -EFAULT;
+			goto done;
+		}
+		prev_pfn = this_pfn;
+	}
+
+	/*
+	 * Memory is contigous, lock vma and return to the caller
+	 */
+	*res_vma = vb2_get_vma(vma);
+	if (*res_vma == NULL) {
+		ret = -ENOMEM;
+		goto done;
+	}
+	*res_pa = pa + offset;
+	ret = 0;
+
+done:
+	up_read(&mm->mmap_sem);
+	return ret;
+}
+
+/**
+ * vb2_mmap_pfn_range() - map physical pages to userspace
+ * @vma:	virtual memory region for the mapping
+ * @paddr:	starting physical address of the memory to be mapped
+ * @size:	size of the memory to be mapped
+ * @vm_ops:	vm operations to be assigned to the created area
+ * @priv:	private data to be associated with the area
+ *
+ * Returns 0 on success.
+ */
+int vb2_mmap_pfn_range(struct vm_area_struct *vma, unsigned long paddr,
+				unsigned long size,
+				const struct vm_operations_struct *vm_ops,
+				void *priv)
+{
+	int ret;
+
+	size = min_t(unsigned long, vma->vm_end - vma->vm_start, size);
+
+	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+	ret = remap_pfn_range(vma, vma->vm_start, paddr >> PAGE_SHIFT,
+				size, vma->vm_page_prot);
+	if (ret) {
+		printk(KERN_ERR "Remapping memory failed, error: %d\n", ret);
+		return ret;
+	}
+
+	vma->vm_flags		|= VM_DONTEXPAND | VM_RESERVED;
+	vma->vm_private_data	= priv;
+	vma->vm_ops		= vm_ops;
+
+	vma->vm_ops->open(vma);
+
+	printk(KERN_DEBUG "%s: mapped paddr 0x%08lx at 0x%08lx, size %ld\n",
+			__func__, paddr, vma->vm_start, size);
+
+	return 0;
+}
+
+/**
+ * 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;
+
+	printk(KERN_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;
+
+	printk(KERN_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");
+MODULE_LICENSE("GPL");