Re: [KJ][RFC][PATCH] BIT macro cleanup

From: Richard Knutsson
Date: Fri Feb 23 2007 - 03:57:13 EST

Milind Choudhary wrote:
Hi all
working towards the cleanup of BIT macro,
I've added one to <linux/bitops.h> & cleaned some obvious users.

include/linux/input.h also has a BIT macro
which does a wrap
so currently i've done something like

+#undef BIT
#define BIT(nr) (1UL << ((nr) % BITS_PER_LONG))

Is it advisible to move this macro to bitops.h with some other name

+#define BITWRAP(nr) (1UL << ((nr) % BITS_PER_LONG))

& make the whole input subsystem use it
The change is huge, more than 125 files using input.h
& almost all use the BIT macro.
It is as a big of change, but have you dismissed the "BIT(nr % BITS_PER_LONG)" approach?
I really think this has to be broken down into a patch-set.

diff --git a/fs/select.c b/fs/select.c
index fe0893a..4bbe8ed 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -180,7 +180,6 @@ get_max:
return max;

-#define BIT(i) (1UL << ((i)&(__NFDBITS-1)))
Are you sure you can just delete this one?

diff --git a/include/linux/input.h b/include/linux/input.h
index bde65c8..e4203d1 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -908,9 +908,11 @@ struct ff_effect {
#include <linux/fs.h>
#include <linux/timer.h>
#include <linux/mod_devicetable.h>
+//#include <linux/bitops.h>
You added and commented it out?

#define NBITS(x) (((x)/BITS_PER_LONG)+1)
-#define BIT(x) (1UL<<((x)%BITS_PER_LONG))
+#undef BIT
+#define BIT(nr) (1UL << ((nr) % BITS_PER_LONG))
Why did you change x to nr? The other defines seems to use x.
#define LONG(x) ((x)/BITS_PER_LONG)

#define INPUT_KEYCODE(dev, scancode) ((dev->keycodesize == 1) ?
((u8*)dev->keycode)[scancode] : \
diff --git a/include/video/sstfb.h b/include/video/sstfb.h
index baa163f..b52f073 100644
--- a/include/video/sstfb.h
+++ b/include/video/sstfb.h
@@ -68,7 +68,6 @@
# define print_var(X,Y...)

-#define BIT(x) (1ul<<(x))
#define POW2(x) (1ul<<(x))
Maybe you can clean up POW2 as well (or define it as "#define POW2(x) BIT(x)")

Also, it seems your mail-client swapped the tabs to spaces (aka not able to apply).

Other then what I have commented on, it looks good.

Richard Knutsson

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at