[PATCH][RFC] Make asm-generic/ioctl.h extensible by adding conditionals.

[Robert P. J. Day]

  Add some preprocessor checking to asm-generic/ioctl.h to allow other
ioctl.h headers to simply override what are normally trivial
differences.

Signed-off-by: Robert P. J. Day <rpjday@xxxxxxxxxxxxxx>

---

  as a followup to my earlier post, is it worth making this change to
allow at least a couple arch-specific ioctl.h files to be massively
simplified?


diff --git a/include/asm-generic/ioctl.h b/include/asm-generic/ioctl.h
index cd02729..e035e6d 100644
--- a/include/asm-generic/ioctl.h
+++ b/include/asm-generic/ioctl.h
@@ -21,8 +21,15 @@
  */
 #define _IOC_NRBITS	8
 #define _IOC_TYPEBITS	8
-#define _IOC_SIZEBITS	14
-#define _IOC_DIRBITS	2
+/*
+ *  Let any architecture override either of the following.
+ */
+#ifndef _IOC_SIZEBITS
+# define _IOC_SIZEBITS	14
+#endif
+#ifndef _IOC_DIRBITS
+# define _IOC_DIRBITS	2
+#endif

 #define _IOC_NRMASK	((1 << _IOC_NRBITS)-1)
 #define _IOC_TYPEMASK	((1 << _IOC_TYPEBITS)-1)
@@ -35,11 +42,17 @@
 #define _IOC_DIRSHIFT	(_IOC_SIZESHIFT+_IOC_SIZEBITS)

 /*
- * Direction bits.
+ * Direction bits, which any architecture can choose to override.
  */
-#define _IOC_NONE	0U
-#define _IOC_WRITE	1U
-#define _IOC_READ	2U
+#ifndef _IOC_NONE
+# define _IOC_NONE	0U
+#endif
+#ifndef _IOC_WRITE
+# define _IOC_WRITE	1U
+#endif
+#ifndef _IOC_READ
+# define _IOC_READ	2U
+#endif

 #define _IOC(dir,type,nr,size) \
 	(((dir)  << _IOC_DIRSHIFT) | \

-- 
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA

http://fsdev.net/wiki/index.php?title=Main_Page
========================================================================
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