s390/bitops: rename find_first_bit_left() to find_first_bit_inv()

find_first_bit_left() and friends have nothing to do with the normal
LSB0 bit numbering for big endian machines used in Linux (least
significant bit has bit number 0).
Instead they use MSB0 bit numbering, where the most signficant bit has
bit number 0. So rename find_first_bit_left() and friends to
find_first_bit_inv(), to avoid any confusion.
Also provide inv versions of set_bit, clear_bit and test_bit.

This also removes the confusing use of e.g. set_bit() in airq.c which
uses a "be_to_le" bit number conversion, which could imply that instead
set_bit_le() could be used. But that is entirely wrong since the _le
bitops variant uses yet another bit numbering scheme.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

3 files changed, 46 insertions, 22 deletions

diff --git a/arch/s390/include/asm/bitops.h b/arch/s390/include/asm/bitops.h
index c6dbd6115cc5..6e6ad0680829 100644
--- a/arch/s390/include/asm/bitops.h
+++ b/arch/s390/include/asm/bitops.h
@@ -300,12 +300,41 @@ static inline int test_bit(unsigned long nr, const volatile unsigned long *ptr)
 }
 
 /*
- * ATTENTION:
- * find_first_bit_left() and find_next_bit_left() use MSB0 encoding.
+ * Functions which use MSB0 bit numbering.
+ * On an s390x system the bits are numbered:
+ *   |0..............63|64............127|128...........191|192...........255|
+ * and on s390:
+ *   |0.....31|31....63|64....95|96...127|128..159|160..191|192..223|224..255|
  */
-unsigned long find_first_bit_left(const unsigned long *addr, unsigned long size);
-unsigned long find_next_bit_left(const unsigned long *addr, unsigned long size,
-				 unsigned long offset);
+unsigned long find_first_bit_inv(const unsigned long *addr, unsigned long size);
+unsigned long find_next_bit_inv(const unsigned long *addr, unsigned long size,
+				unsigned long offset);
+
+static inline void set_bit_inv(unsigned long nr, volatile unsigned long *ptr)
+{
+	return set_bit(nr ^ (BITS_PER_LONG - 1), ptr);
+}
+
+static inline void clear_bit_inv(unsigned long nr, volatile unsigned long *ptr)
+{
+	return clear_bit(nr ^ (BITS_PER_LONG - 1), ptr);
+}
+
+static inline void __set_bit_inv(unsigned long nr, volatile unsigned long *ptr)
+{
+	return __set_bit(nr ^ (BITS_PER_LONG - 1), ptr);
+}
+
+static inline void __clear_bit_inv(unsigned long nr, volatile unsigned long *ptr)
+{
+	return __clear_bit(nr ^ (BITS_PER_LONG - 1), ptr);
+}
+
+static inline int test_bit_inv(unsigned long nr,
+			       const volatile unsigned long *ptr)
+{
+	return test_bit(nr ^ (BITS_PER_LONG - 1), ptr);
+}
 
 #ifdef CONFIG_HAVE_MARCH_Z9_109_FEATURES
 
diff --git a/arch/s390/lib/find.c b/arch/s390/lib/find.c
index 8963929b06b9..620d34d6487e 100644
--- a/arch/s390/lib/find.c
+++ b/arch/s390/lib/find.c
@@ -15,7 +15,7 @@
 #include <linux/bitops.h>
 #include <linux/export.h>
 
-unsigned long find_first_bit_left(const unsigned long *addr, unsigned long size)
+unsigned long find_first_bit_inv(const unsigned long *addr, unsigned long size)
 {
 	const unsigned long *p = addr;
 	unsigned long result = 0;
@@ -35,10 +35,10 @@ unsigned long find_first_bit_left(const unsigned long *addr, unsigned long size)
 found:
 	return result + (__fls(tmp) ^ (BITS_PER_LONG - 1));
 }
-EXPORT_SYMBOL(find_first_bit_left);
+EXPORT_SYMBOL(find_first_bit_inv);
 
-unsigned long find_next_bit_left(const unsigned long *addr, unsigned long size,
-				 unsigned long offset)
+unsigned long find_next_bit_inv(const unsigned long *addr, unsigned long size,
+				unsigned long offset)
 {
 	const unsigned long *p = addr + (offset / BITS_PER_LONG);
 	unsigned long result = offset & ~(BITS_PER_LONG - 1);
@@ -74,4 +74,4 @@ found_first:
 found_middle:
 	return result + (__fls(tmp) ^ (BITS_PER_LONG - 1));
 }
-EXPORT_SYMBOL(find_next_bit_left);
+EXPORT_SYMBOL(find_next_bit_inv);
diff --git a/drivers/s390/cio/airq.c b/drivers/s390/cio/airq.c
index d028fd800c9c..f055df0b167f 100644
--- a/drivers/s390/cio/airq.c
+++ b/drivers/s390/cio/airq.c
@@ -194,15 +194,14 @@ EXPORT_SYMBOL(airq_iv_release);
  */
 unsigned long airq_iv_alloc_bit(struct airq_iv *iv)
 {
-	const unsigned long be_to_le = BITS_PER_LONG - 1;
 	unsigned long bit;
 
 	if (!iv->avail)
 		return -1UL;
 	spin_lock(&iv->lock);
-	bit = find_first_bit_left(iv->avail, iv->bits);
+	bit = find_first_bit_inv(iv->avail, iv->bits);
 	if (bit < iv->bits) {
-		clear_bit(bit ^ be_to_le, iv->avail);
+		clear_bit_inv(bit, iv->avail);
 		if (bit >= iv->end)
 			iv->end = bit + 1;
 	} else
@@ -220,19 +219,17 @@ EXPORT_SYMBOL(airq_iv_alloc_bit);
  */
 void airq_iv_free_bit(struct airq_iv *iv, unsigned long bit)
 {
-	const unsigned long be_to_le = BITS_PER_LONG - 1;
-
 	if (!iv->avail)
 		return;
 	spin_lock(&iv->lock);
 	/* Clear (possibly left over) interrupt bit */
-	clear_bit(bit ^ be_to_le, iv->vector);
+	clear_bit_inv(bit, iv->vector);
 	/* Make the bit position available again */
-	set_bit(bit ^ be_to_le, iv->avail);
+	set_bit_inv(bit, iv->avail);
 	if (bit == iv->end - 1) {
 		/* Find new end of bit-field */
 		while (--iv->end > 0)
-			if (!test_bit((iv->end - 1) ^ be_to_le, iv->avail))
+			if (!test_bit_inv(iv->end - 1, iv->avail))
 				break;
 	}
 	spin_unlock(&iv->lock);
@@ -251,15 +248,13 @@ EXPORT_SYMBOL(airq_iv_free_bit);
 unsigned long airq_iv_scan(struct airq_iv *iv, unsigned long start,
 			   unsigned long end)
 {
-	const unsigned long be_to_le = BITS_PER_LONG - 1;
 	unsigned long bit;
 
 	/* Find non-zero bit starting from 'ivs->next'. */
-	bit = find_next_bit_left(iv->vector, end, start);
+	bit = find_next_bit_inv(iv->vector, end, start);
 	if (bit >= end)
 		return -1UL;
-	/* Clear interrupt bit (find left uses big-endian bit numbers) */
-	clear_bit(bit ^ be_to_le, iv->vector);
+	clear_bit_inv(bit, iv->vector);
 	return bit;
 }
 EXPORT_SYMBOL(airq_iv_scan);