i asked about this a while back, but i still haven't heard a
definitive response as to whether it's acceptable. that is, extending
the header file "asm-generic/ioctl.h" to allow arch-specific ioctl.h
header files to override what little might need to be changed from the
generic file:
==================================================
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) | \
========================================
from just a cursory examination, the only values that seem to ever
need to be different are the ones mentioned above, which would make
some of those arch-specific ioctl.h files *way* shorter than they are
now.
is this considered an acceptable kernel programming practise? or is
it understood that, if an arch-specific header file differs *at* *all*
from the generic one, it will be a *complete* replacement for that
generic version?
rday
p.s. i haven't looked but i'd have to guess that there are some other
header files that could be modified the same way.
--
========================================================================
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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