Support -i partition:file feature for both read and write.

flashrom.c

 /*
  * This file is part of the flashrom project.
  *
  * Copyright (C) 2000 Silicon Integrated System Corporation
  * Copyright (C) 2004 Tyan Corp <yhlu@tyan.com>
  * Copyright (C) 2005-2008 coresystems GmbH
  * Copyright (C) 2008,2009 Carl-Daniel Hailfinger
  *
  * 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
@@ skipping 1298 matching lines @@
                 return 1;
         }
         return 0;
 }
 
 int read_flash_to_file(struct flashchip *flash, char *filename)
 {
         unsigned long size = flash->total_size * 1024;
         unsigned char *buf = calloc(size, sizeof(char));
         int ret = 0;
+        int i;
 
         msg_cinfo("Reading flash... ");
         if (!buf) {
                 msg_gerr("Memory allocation failed!\n");
                 msg_cinfo("FAILED.\n");
                 return 1;
         }
+
+        /* To support partial read, fill buffer to all 0xFF at beginning to make
+         * debug easier. */
+        memset(buf, 0xFF, size);
+
         if (!flash->read) {
                 msg_cerr("No read function available for this flash chip.\n");
                 ret = 1;
                 goto out_free;
         }
-        if (flash->read(flash, buf, 0, size)) {
+
+        /* First try to handle partial read case, rather than read the whole
+         * flash, which is slow. */
+        ret = handle_partial_read(flash, buf, flash->read);
+        if (ret < 0) {
+                msg_cerr("Partial read operation failed!\n");
+                ret = 1;
+                goto out_free;
+        } else if (ret > 0) {
+                /* Partial read has been handled, pass the whole flash read. */
+        } else if (flash->read(flash, buf, 0, size)) {
                 msg_cerr("Read operation failed!\n");
                 ret = 1;
                 goto out_free;
         }
 
         ret = write_buf_to_file(buf, flash->total_size * 1024, filename);
 out_free:
         free(buf);
         if (ret)
                 msg_cerr("FAILED.");
@@ skipping 638 matching lines @@
 out_nofree:
         chip_restore(); /* must be done before programmer_shutdown() */
         /*
          * programmer_shutdown() call is moved to cli_mfg() in chromium os
          * tree. This is because some operations, such as write protection,
          * requires programmer_shutdown() but does not call doit().
          */
 //      programmer_shutdown();
         return ret;
 }