[PATCH] Small kernel-api addition

[PATCH] Small kernel-api addition

[John Levon]

Clean against 2.4.4-ac6 and 2.4.4

thanks
john


--- Documentation/DocBook/kernel-api.tmpl.old	Thu May 10 18:02:05 2001
+++ Documentation/DocBook/kernel-api.tmpl	Thu May 10 18:02:57 2001
@@ -41,8 +41,9 @@
 !Iinclude/linux/init.h
      </sect1>
 
-     <sect1><title>Atomics</title>
+     <sect1><title>Atomic and pointer manipulation</title>
 !Iinclude/asm-i386/atomic.h
+!Iinclude/asm-i386/unaligned.h
      </sect1>
 
      <sect1><title>Delaying, scheduling, and timer routines</title>
--- include/asm-i386/unaligned.h.old	Thu May 10 17:54:28 2001
+++ include/asm-i386/unaligned.h	Thu May 10 18:29:11 2001
@@ -9,8 +9,29 @@
  * architectures where unaligned accesses aren't as simple.
  */
 
+/**
+ * get_unaligned - get value from possibly mis-aligned location
+ * @ptr: pointer to value
+ *
+ * This macro should be used for accessing values larger in size than single
+ * bytes at locations that may be improperly aligned, e.g. retrieving a u16
+ * value from a location not u16-aligned.
+ *
+ * Note that unaligned accesses can be very expensive on some architectures.
+ */
 #define get_unaligned(ptr) (*(ptr))
 
+/**
+ * put_unaligned - put value to a possibly mis-aligned location
+ * @val: value to place
+ * @ptr: pointer to location
+ *
+ * This macro should be used for placing values larger in size than single
+ * bytes at locations that may be improperly aligned, e.g. write a u16
+ * value to a location not u16-aligned.
+ *
+ * Note that unaligned accesses can be very expensive on some architectures.
+ */
 #define put_unaligned(val, ptr) ((void)( *(ptr) = (val) ))
 
 #endif

Re: [PATCH] Small kernel-api addition

[David Woodhouse]

moz@compsoc.man.ac.uk said:
+ * This macro should be used for accessing values larger in size than single
+ * bytes at locations that may be improperly aligned, e.g. retrieving a u16 
+ * value from a location not u16-aligned. 

I'd suggest s/that may be/that are expected to be/

If it's _expected_, then by all means use {get,put}_unaligned(). If it's 
normally going to be aligned, and it _may_ occasionally be otherwise, let 
the common case go fast, and let the fixup handle it otherwise.


--
dwmw2

Re: [PATCH] Small kernel-api addition

[John Levon]

On Thu, 10 May 2001, David Woodhouse wrote:

> I'd suggest s/that may be/that are expected to be/

thanks, how about this :

--- Documentation/DocBook/kernel-api.tmpl.old	Thu May 10 18:02:05 2001
+++ Documentation/DocBook/kernel-api.tmpl	Thu May 10 18:02:57 2001
@@ -41,8 +41,9 @@
 !Iinclude/linux/init.h
      </sect1>
 
-     <sect1><title>Atomics</title>
+     <sect1><title>Atomic and pointer manipulation</title>
 !Iinclude/asm-i386/atomic.h
+!Iinclude/asm-i386/unaligned.h
      </sect1>
 
      <sect1><title>Delaying, scheduling, and timer routines</title>
--- include/asm-i386/unaligned.h.old	Thu May 10 17:54:28 2001
+++ include/asm-i386/unaligned.h	Thu May 10 19:38:55 2001
@@ -9,8 +9,29 @@
  * architectures where unaligned accesses aren't as simple.
  */
 
+/**
+ * get_unaligned - get value from possibly mis-aligned location
+ * @ptr: pointer to value
+ *
+ * This macro should be used for accessing values larger in size than 
+ * single bytes at locations that are expected to be improperly aligned, 
+ * e.g. retrieving a u16 value from a location not u16-aligned.
+ *
+ * Note that unaligned accesses can be very expensive on some architectures.
+ */
 #define get_unaligned(ptr) (*(ptr))
 
+/**
+ * put_unaligned - put value to a possibly mis-aligned location
+ * @val: value to place
+ * @ptr: pointer to location
+ *
+ * This macro should be used for placing values larger in size than 
+ * single bytes at locations that are expected to be improperly aligned, 
+ * e.g. writing a u16 value to a location not u16-aligned.
+ *
+ * Note that unaligned accesses can be very expensive on some architectures.
+ */
 #define put_unaligned(val, ptr) ((void)( *(ptr) = (val) ))
 
 #endif