diff mbox

[1/2,v2] lib: int_sqrt: add int64_sqrt routine

Message ID 1404390870-24062-1-git-send-email-21cnbao@gmail.com (mailing list archive)
State New, archived
Headers show

Commit Message

Barry Song July 3, 2014, 12:34 p.m. UTC 
From: Yibo Cai <yibo.cai@csr.com>

Get square root of a 64-bit digit on 32bit platforms. CSR SiRFSoC
touchscreen driver needs it.

Cc: Peter Meerwald <pmeerw@pmeerw.net>
Signed-off-by: Yibo Cai <yibo.cai@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
---
 -v2:
 use CONFIG_64BIT MARCO
 don't init for b, m

 include/linux/kernel.h |  8 ++++++++
 lib/int_sqrt.c         | 25 +++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

Comments

Andrew Morton July 8, 2014, 9:55 p.m. UTC | #1 
On Thu,  3 Jul 2014 20:34:30 +0800 Barry Song <21cnbao@gmail.com> wrote:

> Get square root of a 64-bit digit on 32bit platforms. CSR SiRFSoC
> touchscreen driver needs it.

Looks OK to me.  Can this be carried in whatever tree holds the "CSR
SiRFSoC touchscreen driver"?
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Dmitry Torokhov July 8, 2014, 10:12 p.m. UTC | #2 
On Tue, Jul 08, 2014 at 02:55:01PM -0700, Andrew Morton wrote:
> On Thu,  3 Jul 2014 20:34:30 +0800 Barry Song <21cnbao@gmail.com> wrote:
> 
> > Get square root of a 64-bit digit on 32bit platforms. CSR SiRFSoC
> > touchscreen driver needs it.
> 
> Looks OK to me.  Can this be carried in whatever tree holds the "CSR
> SiRFSoC touchscreen driver"?

Yeah, I'll pick it up.
diff mbox

Patch

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 4c52907..a536c0c 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -418,6 +418,14 @@  struct pid;
 extern struct pid *session_of_pgrp(struct pid *pgrp);
 
 unsigned long int_sqrt(unsigned long);
+#ifdef CONFIG_64BIT
+static inline unsigned long long int64_sqrt(unsigned long long x)
+{
+	return int_sqrt(x);
+}
+#else
+unsigned long long int64_sqrt(unsigned long long);
+#endif
 
 extern void bust_spinlocks(int yes);
 extern int oops_in_progress;		/* If set, an oops, panic(), BUG() or die() is in progress */
diff --git a/lib/int_sqrt.c b/lib/int_sqrt.c
index 1ef4cc3..b86cccb 100644
--- a/lib/int_sqrt.c
+++ b/lib/int_sqrt.c
@@ -36,3 +36,28 @@  unsigned long int_sqrt(unsigned long x)
 	return y;
 }
 EXPORT_SYMBOL(int_sqrt);
+
+#ifndef CONFIG_64BIT
+unsigned long long int64_sqrt(unsigned long long x)
+{
+	unsigned long long b, m, y = 0;
+
+	if (x <= 1)
+		return x;
+
+	m = 1ULL << (BITS_PER_LONG_LONG - 2);
+	while (m != 0) {
+		b = y + m;
+		y >>= 1;
+
+		if (x >= b) {
+			x -= b;
+			y += m;
+		}
+		m >>= 2;
+	}
+
+	return y;
+}
+EXPORT_SYMBOL(int64_sqrt);
+#endif