util.c

   1 /*
   2  * Copyright (c) 2011 Maxim Levitsky
   3  *
   4  * This file is part of linux cryptodev.
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version 2
   9  * of the License, or (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc.,
  19  * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  20  */
  21
  22 #include <crypto/scatterwalk.h>
  23 #include <linux/scatterlist.h>
  24 #include "util.h"
  25
  26 /* These were taken from Maxim Levitsky's patch to lkml.
  27  */
  28 struct scatterlist *sg_advance(struct scatterlist *sg, int consumed)
  29 {
  30         while (consumed >= sg->length) {
  31                 consumed -= sg->length;
  32
  33                 sg = sg_next(sg);
  34                 if (!sg)
  35                         break;
  36         }
  37
  38         WARN_ON(!sg && consumed);
  39
  40         if (!sg)
  41                 return NULL;
  42
  43         sg->offset += consumed;
  44         sg->length -= consumed;
  45
  46         if (sg->offset >= PAGE_SIZE) {
  47                 struct page *page =
  48                         nth_page(sg_page(sg), sg->offset / PAGE_SIZE);
  49                 sg_set_page(sg, page, sg->length, sg->offset % PAGE_SIZE);
  50         }
  51
  52         return sg;
  53 }
  54
  55 /**
  56  * sg_copy - copies sg entries from sg_from to sg_to, such
  57  * as sg_to covers first 'len' bytes from sg_from.
  58  */
  59 int sg_copy(struct scatterlist *sg_from, struct scatterlist *sg_to, int len)
  60 {
  61         while (len > sg_from->length) {
  62                 len -= sg_from->length;
  63
  64                 sg_set_page(sg_to, sg_page(sg_from),
  65                                 sg_from->length, sg_from->offset);
  66
  67                 sg_to = sg_next(sg_to);
  68                 sg_from = sg_next(sg_from);
  69
  70                 if (len && (!sg_from || !sg_to))
  71                         return -ENOMEM;
  72         }
  73
  74         if (len)
  75                 sg_set_page(sg_to, sg_page(sg_from),
  76                                 len, sg_from->offset);
  77         sg_mark_end(sg_to);
  78         return 0;
  79 }
  80