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

   1 /*
   2  * videobuf2-memops.c - generic memory handling routines for videobuf2
   3  *
   4  * Copyright (C) 2010 Samsung Electronics
   5  *
   6  * Author: Pawel Osciak <pawel@osciak.com>
   7  *         Marek Szyprowski <m.szyprowski@samsung.com>
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation.
  12  */
  13
  14 #include <linux/slab.h>
  15 #include <linux/module.h>
  16 #include <linux/dma-mapping.h>
  17 #include <linux/vmalloc.h>
  18 #include <linux/mm.h>
  19 #include <linux/sched.h>
  20 #include <linux/file.h>
  21
  22 #include <media/videobuf2-core.h>
  23 #include <media/videobuf2-memops.h>
  24
  25 /**
  26  * vb2_get_vma() - acquire and lock the virtual memory area
  27  * @vma:        given virtual memory area
  28  *
  29  * This function attempts to acquire an area mapped in the userspace for
  30  * the duration of a hardware operation. The area is "locked" by performing
  31  * the same set of operation that are done when process calls fork() and
  32  * memory areas are duplicated.
  33  *
  34  * Returns a copy of a virtual memory region on success or NULL.
  35  */
  36 struct vm_area_struct *vb2_get_vma(struct vm_area_struct *vma)
  37 {
  38         struct vm_area_struct *vma_copy;
  39
  40         vma_copy = kmalloc(sizeof(*vma_copy), GFP_KERNEL);
  41         if (vma_copy == NULL)
  42                 return NULL;
  43
  44         if (vma->vm_ops && vma->vm_ops->open)
  45                 vma->vm_ops->open(vma);
  46
  47         if (vma->vm_file)
  48                 get_file(vma->vm_file);
  49
  50         memcpy(vma_copy, vma, sizeof(*vma));
  51
  52         vma_copy->vm_mm = NULL;
  53         vma_copy->vm_next = NULL;
  54         vma_copy->vm_prev = NULL;
  55
  56         return vma_copy;
  57 }
  58 EXPORT_SYMBOL_GPL(vb2_get_vma);
  59
  60 /**
  61  * vb2_put_userptr() - release a userspace virtual memory area
  62  * @vma:        virtual memory region associated with the area to be released
  63  *
  64  * This function releases the previously acquired memory area after a hardware
  65  * operation.
  66  */
  67 void vb2_put_vma(struct vm_area_struct *vma)
  68 {
  69         if (!vma)
  70                 return;
  71
  72         if (vma->vm_ops && vma->vm_ops->close)
  73                 vma->vm_ops->close(vma);
  74
  75         if (vma->vm_file)
  76                 fput(vma->vm_file);
  77
  78         kfree(vma);
  79 }
  80 EXPORT_SYMBOL_GPL(vb2_put_vma);
  81
  82 /**
  83  * vb2_get_contig_userptr() - lock physically contiguous userspace mapped memory
  84  * @vaddr:      starting virtual address of the area to be verified
  85  * @size:       size of the area
  86  * @res_paddr:  will return physical address for the given vaddr
  87  * @res_vma:    will return locked copy of struct vm_area for the given area
  88  *
  89  * This function will go through memory area of size @size mapped at @vaddr and
  90  * verify that the underlying physical pages are contiguous. If they are
  91  * contiguous the virtual memory area is locked and a @res_vma is filled with
  92  * the copy and @res_pa set to the physical address of the buffer.
  93  *
  94  * Returns 0 on success.
  95  */
  96 int vb2_get_contig_userptr(unsigned long vaddr, unsigned long size,
  97                            struct vm_area_struct **res_vma, dma_addr_t *res_pa)
  98 {
  99         struct mm_struct *mm = current->mm;
 100         struct vm_area_struct *vma;
 101         unsigned long offset, start, end;
 102         unsigned long this_pfn, prev_pfn;
 103         dma_addr_t pa = 0;
 104
 105         start = vaddr;
 106         offset = start & ~PAGE_MASK;
 107         end = start + size;
 108
 109         vma = find_vma(mm, start);
 110
 111         if (vma == NULL || vma->vm_end < end)
 112                 return -EFAULT;
 113
 114         for (prev_pfn = 0; start < end; start += PAGE_SIZE) {
 115                 int ret = follow_pfn(vma, start, &this_pfn);
 116                 if (ret)
 117                         return ret;
 118
 119                 if (prev_pfn == 0)
 120                         pa = this_pfn << PAGE_SHIFT;
 121                 else if (this_pfn != prev_pfn + 1)
 122                         return -EFAULT;
 123
 124                 prev_pfn = this_pfn;
 125         }
 126
 127         /*
 128          * Memory is contigous, lock vma and return to the caller
 129          */
 130         *res_vma = vb2_get_vma(vma);
 131         if (*res_vma == NULL)
 132                 return -ENOMEM;
 133
 134         *res_pa = pa + offset;
 135         return 0;
 136 }
 137 EXPORT_SYMBOL_GPL(vb2_get_contig_userptr);
 138
 139 /**
 140  * vb2_common_vm_open() - increase refcount of the vma
 141  * @vma:        virtual memory region for the mapping
 142  *
 143  * This function adds another user to the provided vma. It expects
 144  * struct vb2_vmarea_handler pointer in vma->vm_private_data.
 145  */
 146 static void vb2_common_vm_open(struct vm_area_struct *vma)
 147 {
 148         struct vb2_vmarea_handler *h = vma->vm_private_data;
 149
 150         pr_debug("%s: %p, refcount: %d, vma: %08lx-%08lx\n",
 151                __func__, h, atomic_read(h->refcount), vma->vm_start,
 152                vma->vm_end);
 153
 154         atomic_inc(h->refcount);
 155 }
 156
 157 /**
 158  * vb2_common_vm_close() - decrease refcount of the vma
 159  * @vma:        virtual memory region for the mapping
 160  *
 161  * This function releases the user from the provided vma. It expects
 162  * struct vb2_vmarea_handler pointer in vma->vm_private_data.
 163  */
 164 static void vb2_common_vm_close(struct vm_area_struct *vma)
 165 {
 166         struct vb2_vmarea_handler *h = vma->vm_private_data;
 167
 168         pr_debug("%s: %p, refcount: %d, vma: %08lx-%08lx\n",
 169                __func__, h, atomic_read(h->refcount), vma->vm_start,
 170                vma->vm_end);
 171
 172         h->put(h->arg);
 173 }
 174
 175 /**
 176  * vb2_common_vm_ops - common vm_ops used for tracking refcount of mmaped
 177  * video buffers
 178  */
 179 const struct vm_operations_struct vb2_common_vm_ops = {
 180         .open = vb2_common_vm_open,
 181         .close = vb2_common_vm_close,
 182 };
 183 EXPORT_SYMBOL_GPL(vb2_common_vm_ops);
 184
 185 MODULE_DESCRIPTION("common memory handling routines for videobuf2");
 186 MODULE_AUTHOR("Pawel Osciak <pawel@osciak.com>");
 187 MODULE_LICENSE("GPL");