patch-2.4.20 linux-2.4.20/include/asm-i386/scatterlist.h

• Lines: 25
• Date: Thu Nov 28 15:53:15 2002
• Orig file: linux-2.4.19/include/asm-i386/scatterlist.h
• Orig date: Fri Oct 12 15:35:54 2001

diff -urN linux-2.4.19/include/asm-i386/scatterlist.h linux-2.4.20/include/asm-i386/scatterlist.h
@@ -1,6 +1,24 @@
 #ifndef _I386_SCATTERLIST_H
 #define _I386_SCATTERLIST_H
 
+/*
+ * Drivers must set either ->address or (preferred) ->page and ->offset
+ * to indicate where data must be transferred to/from.
+ *
+ * Using ->page is recommended since it handles highmem data as well as
+ * low mem. ->address is restricted to data which has a virtual mapping, and
+ * it will go away in the future. Updating to ->page can be automated very
+ * easily -- something like
+ *
+ * sg->address = some_ptr;
+ *
+ * can be rewritten as
+ *
+ * sg->page = virt_to_page(some_ptr);
+ * sg->offset = (unsigned long) some_ptr & ~PAGE_MASK;
+ *
+ * and that's it. There's no excuse for not highmem enabling YOUR driver. /jens
+ */
 struct scatterlist {
     char *  address;    /* Location data is to be transferred to, NULL for
 			 * highmem page */