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lib: Add strongly typed 64bit int_sqrt

PATCH Superseded Crt Mori 2 participants 3 messages Dec 20, 2017

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Library code IIO

v9 of 13 Superseded Latest is v13 →

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Crt Mori

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#0 lore raw

PATCH v9 1/3 lib: Add strongly typed 64bit int_sqrt

There is no option to perform 64bit integer sqrt on 32bit platform. Added stronger typed int_sqrt64 enables the 64bit calculations to be performed on 32bit platforms. Although int_sqrt() is a rough approximation, the same algorithm is used in int_sqrt64() as good enough on 32bit platform.

Signed-off-by Crt Mori <[email protected]>
---
 include/linux/kernel.h |  1 +
 lib/int_sqrt.c         | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)
include/linux/kernel.h +1 -0
index 0ad4c3044cf9..5c6949e9e309 100644
@@ -459,6 +459,7 @@ extern int kernel_text_address(unsigned long addr);
 extern int func_ptr_is_kernel_text(void *ptr);
 
 unsigned long int_sqrt(unsigned long);
+u32 int_sqrt64(u64 x);
 
 extern void bust_spinlocks(int yes);
 extern int oops_in_progress;		/* If set, an oops, panic(), BUG() or die() is in progress */
lib/int_sqrt.c +37 -0
index 1ef4cc344977..30acab761dc1 100644
@@ -7,6 +7,7 @@
 
 #include <linux/kernel.h>
 #include <linux/export.h>
+#include <linux/bitops.h>
 
 /**
  * int_sqrt - rough approximation to sqrt

@@ -36,3 +37,39 @@ unsigned long int_sqrt(unsigned long x)
 	return y;
 }
 EXPORT_SYMBOL(int_sqrt);
+
+#if BITS_PER_LONG < 64
+/**
+ * int_sqrt64 - strongly typed int_sqrt function when minimum 64 bit input
+ * is expected.
+ * @x: 64bit integer of which to calculate the sqrt
+ */
+u32 int_sqrt64(u64 x)
+{
+	u64 b, m, y = 0;
+
+	if (x <= 1)
+		return x;
+
+	m = 1ULL << (fls64(x) & ~1ULL);
+	while (m != 0) {
+		b = y + m;
+		y >>= 1;
+
+		if (x >= b) {
+			x -= b;
+			y += m;
+		}
+		m >>= 2;
+	}
+
+	return y;
+}
+EXPORT_SYMBOL(int_sqrt64);
+#else
+u32 int_sqrt64(u64 x)
+{
+	return int_sqrt(x);
+}
+EXPORT_SYMBOL(int_sqrt64);
+#endif
Signature · 1 line
2.15.0
#1 lore raw
Quoted 5 lines · Crt Mori

There is no option to perform 64bit integer sqrt on 32bit platform. Added stronger typed int_sqrt64 enables the 64bit calculations to be performed on 32bit platforms. Although int_sqrt() is a rough approximation, the same algorithm is used in int_sqrt64() as good enough on 32bit platform.

[]

include/linux/kernel.h

Quoted 1 line
include/linux/kernel.h +0 -0

[]

include/linux/kernel.h extern int kernel_text_address(unsigned long addr); · line 462

Quoted 5 lines
include/linux/kernel.h +1 -0
@@ -459,6 +459,7 @@ extern int kernel_text_address(unsigned long addr);
 extern int func_ptr_is_kernel_text(void *ptr);
 
 unsigned long int_sqrt(unsigned long);
+u32 int_sqrt64(u64 x);

#ifdef BITS_PER_LONG == 64
static inline u32 int_sqrt64(u64 x)
{
re
turn (u32)int_sqrt(x);
}
#else
u32 int_sqrt64(u64 x);
#endif

[]

Quoted 25 lines
include/linux/kernel.h +25 -0
+#if BITS_PER_LONG < 64
+/**
+ * int_sqrt64 - strongly typed int_sqrt function when minimum 64 bit input
+ * is expected.
+ * @x: 64bit integer of which to calculate the sqrt
+ */
+u32 int_sqrt64(u64 x)
+{
+	u64 b, m, y = 0;
+
+	if (x <= 1)
+		return x;
+
+	m = 1ULL << (fls64(x) & ~1ULL);
+	while (m != 0) {
+		b = y + m;
+		y >>= 1;
+
+		if (x >= b) {
+			x -= b;
+			y += m;
+		}
+		m >>= 2;
+	}
+

include/linux/kernel.h extern int kernel_text_address(unsigned long addr);

Quoted 10 lines
include/linux/kernel.h +10 -0
+	return y;
+}
+EXPORT_SYMBOL(int_sqrt64);
+#else
+u32 int_sqrt64(u64 x)
+{
+	return int_sqrt(x);
+}
+EXPORT_SYMBOL(int_sqrt64);
+#endif

This doesn't need to be EXPORT_SYMBOL for the
BITS_PER_LONG == 64 case

author
#2 lore raw
Quoted 25 lines · Joe Perches
Quoted 5 lines · Crt Mori

There is no option to perform 64bit integer sqrt on 32bit platform. Added stronger typed int_sqrt64 enables the 64bit calculations to be performed on 32bit platforms. Although int_sqrt() is a rough approximation, the same algorithm is used in int_sqrt64() as good enough on 32bit platform.

[]

include/linux/kernel.h

Quoted 1 line
include/linux/kernel.h +0 -0

[]

include/linux/kernel.h extern int kernel_text_address(unsigned long addr); · line 462

Quoted 5 lines
include/linux/kernel.h +1 -0
@@ -459,6 +459,7 @@ extern int kernel_text_address(unsigned long addr);
 extern int func_ptr_is_kernel_text(void *ptr);
 
 unsigned long int_sqrt(unsigned long);
+u32 int_sqrt64(u64 x);

#ifdef BITS_PER_LONG == 64
static inline u32 int_sqrt64(u64 x)
{
re
turn (u32)int_sqrt(x);
}
#else
u32 int_sqrt64(u64 x);
#endif

Quoted 2 lines

[]

OK, fixing it in v10.

Quoted 39 lines
Quoted 25 lines
include/linux/kernel.h +25 -0
+#if BITS_PER_LONG < 64
+/**
+ * int_sqrt64 - strongly typed int_sqrt function when minimum 64 bit input
+ * is expected.
+ * @x: 64bit integer of which to calculate the sqrt
+ */
+u32 int_sqrt64(u64 x)
+{
+     u64 b, m, y = 0;
+
+     if (x <= 1)
+             return x;
+
+     m = 1ULL << (fls64(x) & ~1ULL);
+     while (m != 0) {
+             b = y + m;
+             y >>= 1;
+
+             if (x >= b) {
+                     x -= b;
+                     y += m;
+             }
+             m >>= 2;
+     }
+

include/linux/kernel.h extern int kernel_text_address(unsigned long addr);

Quoted 10 lines
include/linux/kernel.h +10 -0
+     return y;
+}
+EXPORT_SYMBOL(int_sqrt64);
+#else
+u32 int_sqrt64(u64 x)
+{
+     return int_sqrt(x);
+}
+EXPORT_SYMBOL(int_sqrt64);
+#endif

This doesn't need to be EXPORT_SYMBOL for the
BITS_PER_LONG == 64 case