[PATCH 1/2] lib: int_sqrt: add int64_sqrt routine
flat view
STALE4487d
From: Barry Song <hidden>
Date: 2014-06-23 09:44:23
Subsystem:
library code, the rest · Maintainers:
Andrew Morton, Linus Torvalds
From: Yibo Cai <redacted> Get square root of a 64-bit digit on 32bit platforms. CSR SiRFSoC touchscreen driver needs it. Signed-off-by: Yibo Cai <redacted> Signed-off-by: Barry Song <redacted> --- include/linux/kernel.h | 1 + lib/int_sqrt.c | 27 +++++++++++++++++++++++++++ 2 files changed, 28 insertions(+)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 4c52907..6e63081 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h@@ -418,6 +418,7 @@ struct pid; extern struct pid *session_of_pgrp(struct pid *pgrp); unsigned long int_sqrt(unsigned long); +unsigned long long int64_sqrt(unsigned long long); 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..2aa9fcc 100644
--- a/lib/int_sqrt.c
+++ b/lib/int_sqrt.c@@ -36,3 +36,30 @@ unsigned long int_sqrt(unsigned long x) return y; } EXPORT_SYMBOL(int_sqrt); + +/* + * Square root of a 64-bit digit. + * Same as int_sqrt on 64-bit platforms where "long" equals "long long" + */ +unsigned long long int64_sqrt(unsigned long long x) +{ + unsigned long long m = 0, y = 0, b = 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);
--
1.9.3