From 2262cfeef91458b01a1bfe3812ccbbfdf8b82807 Mon Sep 17 00:00:00 2001
From: wdenk <wdenk>
Date: Mon, 18 Nov 2002 00:14:45 +0000
Subject: =?UTF-8?q?*=20Patch=20by=20Daniel=20Engstr=F6m,=2013=20Nov=202002?=
 =?UTF-8?q?:=20=20=20Add=20support=20for=20i386=20architecture=20and=20AMD?=
 =?UTF-8?q?=20SC520=20board?=
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* Patch by Pierre Aubert, 12 Nov 2002:
  Add support for DOS filesystem and booting from DOS floppy disk
---
 fs/fdos/fat.c | 145 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 145 insertions(+)
 create mode 100644 fs/fdos/fat.c

(limited to 'fs/fdos/fat.c')

diff --git a/fs/fdos/fat.c b/fs/fdos/fat.c
new file mode 100644
index 0000000000..42df755af3
--- /dev/null
+++ b/fs/fdos/fat.c
@@ -0,0 +1,145 @@
+/*
+ * (C) Copyright 2002
+ * Stäubli Faverges - <www.staubli.com>
+ * Pierre AUBERT  p.aubert@staubli.com
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * 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; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#include <common.h>
+#include <config.h>
+#include <malloc.h>
+
+#if (CONFIG_COMMANDS & CFG_CMD_FDOS)
+
+#include "dos.h"
+#include "fdos.h"
+
+
+/*-----------------------------------------------------------------------------
+ * fat_decode -- 
+ *-----------------------------------------------------------------------------
+ */
+unsigned int fat_decode (Fs_t *fs, unsigned int num)
+{
+    unsigned int start = num * 3 / 2;
+    unsigned char *address = fs -> fat_buf + start;
+    
+    if (num < 2 || start + 1 > (fs -> fat_len * SZ_STD_SECTOR))
+        return 1;
+    
+    if (num & 1)
+        return ((address [1] & 0xff) << 4) | ((address [0] & 0xf0 ) >> 4);
+    else
+        return ((address [1] & 0xf) << 8) | (address [0] & 0xff );
+}
+/*-----------------------------------------------------------------------------
+ * check_fat -- 
+ *-----------------------------------------------------------------------------
+ */
+static int check_fat (Fs_t *fs)
+{
+    int i, f;
+
+    /* Cluster verification                                                  */
+    for (i = 3 ; i < fs -> num_clus; i++){
+        f = fat_decode (fs, i);
+        if (f < FAT12_LAST && f > fs -> num_clus){
+            /* Wrong cluster number detected                                 */
+            return (-1);
+        }
+    }
+    return (0);
+}
+/*-----------------------------------------------------------------------------
+ * read_one_fat -- 
+ *-----------------------------------------------------------------------------
+ */
+static int read_one_fat (BootSector_t *boot, Fs_t *fs, int nfat)
+{
+    if (dev_read (fs -> fat_buf,
+                  (fs -> fat_start + nfat * fs -> fat_len),
+                  fs -> fat_len) < 0) {
+        return (-1);
+    }
+
+    if (fs -> fat_buf [0] || fs -> fat_buf [1] || fs -> fat_buf [2]) {
+        if ((fs -> fat_buf [0] != boot -> descr &&
+             (fs -> fat_buf [0] != 0xf9 || boot -> descr != MEDIA_STD)) ||
+            fs -> fat_buf [0] < MEDIA_STD){
+            /* Unknown Media                                                 */
+            return (-1);
+        }
+        if (fs -> fat_buf [1] != 0xff || fs -> fat_buf [2] != 0xff){
+            /* FAT doesn't start with good values                            */
+            return (-1);
+        }
+    }
+
+    if (fs -> num_clus >= FAT12_MAX_NB) {
+        /* Too much clusters                                                 */
+        return (-1);
+    }
+
+    return check_fat (fs);
+}
+/*-----------------------------------------------------------------------------
+ * read_fat -- 
+ *-----------------------------------------------------------------------------
+ */
+int read_fat (BootSector_t *boot, Fs_t *fs)
+{
+    unsigned int buflen;
+    int i;
+
+    /* Allocate Fat Buffer                                                   */
+    buflen = fs -> fat_len * SZ_STD_SECTOR;
+    if (fs -> fat_buf) {
+        free (fs -> fat_buf);
+    }
+
+    if ((fs -> fat_buf = malloc (buflen)) == NULL) {
+        return (-1);
+    }
+
+    /* Try to read each Fat                                                  */
+    for (i = 0; i< fs -> nb_fat; i++){
+        if (read_one_fat (boot, fs, i) == 0) {
+            /* Fat is OK                                                     */
+            fs -> num_fat = i;
+            break;
+        }
+    }
+
+    if (i == fs -> nb_fat){
+        return (-1);
+    }
+    
+    if (fs -> fat_len > (((fs -> num_clus + 2) *
+                          (FAT_BITS / 4) -1 ) / 2 /
+                         SZ_STD_SECTOR + 1)) {
+        return (-1);
+    }
+    return (0);
+}
+
+
+ 
+
+#endif
-- 
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