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