RE: [PATCH 1/2] lib: int_sqrt: add int64_sqrt routine
From: Yibo Cai <hidden>
Date: 2014-06-24 05:22:17
Hello Peter,
quoted
Get square root of a 64-bit digit on 32bit platforms. CSR SiRFSoC touchscreen driver needs it.
maybe the code could be #MACRO()'d to avoid duplication
Do you mean to define int64_sqrt() directly as int_sqrt() on a 64 bit platform where sizeof(long) == sizeof(long long)? Yibo ________________________________________ From: Peter Meerwald [pmeerw@pmeerw.net] Sent: Monday, June 23, 2014 5:52 PM To: Barry Song Cc: dmitry.torokhov@gmail.com; dtor@mail.ru; akpm@linux-foundation.org; linux-input@vger.kernel.org; DL-SHA-WorkGroupLinux; Yibo Cai; Barry Song Subject: Re: [PATCH 1/2] lib: int_sqrt: add int64_sqrt routine
Get square root of a 64-bit digit on 32bit platforms. CSR SiRFSoC touchscreen driver needs it.
maybe the code could be #MACRO()'d to avoid duplication see comment below
quoted hunk ↗ jump to hunk
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;
initialization for b, m not needed the original int_sqrt() code correctly skips initialization
+
+ 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);-- Peter Meerwald +43-664-2444418 (mobile) To report this email as spam click https://www.mailcontrol.com/sr/MZbqvYs5QwJvpeaetUwhCQ== . Member of the CSR plc group of companies. CSR plc registered in England and Wales, registered number 4187346, registered office Churchill House, Cambridge Business Park, Cowley Road, Cambridge, CB4 0WZ, United Kingdom More information can be found at www.csr.com. Keep up to date with CSR on our technical blog, www.csr.com/blog, CSR people blog, www.csr.com/people, YouTube, www.youtube.com/user/CSRplc, Facebook, www.facebook.com/pages/CSR/191038434253534, or follow us on Twitter at www.twitter.com/CSR_plc. New for 2014, you can now access the wide range of products powered by aptX at www.aptx.com.