| Message ID | 20171219155908.29528-1-cmo@melexis.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, 2017-12-19 at 16:59 +0100, Crt Mori wrote: > 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 <cmo@melexis.com> > --- > include/linux/kernel.h | 6 ++++++ > lib/int_sqrt.c | 32 ++++++++++++++++++++++++++++++++ > 2 files changed, 38 insertions(+) > > diff --git a/include/linux/kernel.h b/include/linux/kernel.h > index 0ad4c3044cf9..f3bebd3a9213 100644 > --- a/include/linux/kernel.h > +++ b/include/linux/kernel.h > @@ -459,6 +459,12 @@ extern int kernel_text_address(unsigned long addr); > extern int func_ptr_is_kernel_text(void *ptr); > > unsigned long int_sqrt(unsigned long); > +#if BITS_PER_LONG != 64 > +#define int_sqrt64 _int_sqrt64 > +u32 _int_sqrt64(u64 x); > +#else > +#define int_sqrt64 int_sqrt > +#endif As you've changed the return type for the 64-bit function to u32, there is a unsigned long / u32 return mismatch on 64 bit platforms. I suspect you need to define this as: #define int_sqrt64(x) ((u32)int_sqrt(x)) > diff --git a/lib/int_sqrt.c b/lib/int_sqrt.c [] > @@ -36,3 +36,35 @@ 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 << (64 - 2); Should probably use fls64 here. > + while (m != 0) { > + b = y + m; > + y >>= 1; > + > + if (x >= b) { > + x -= b; > + y += m; > + } > + m >>= 2; > + } > + > + return y; > +} > +EXPORT_SYMBOL(_int_sqrt64); > +#endif > + -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Dec 19, 2017 at 08:09:53AM -0800, Joe Perches wrote: > > I suspect you need to define this as: > > #define int_sqrt64(x) ((u32)int_sqrt(x)) What's wrong with using C ? static inline u32 int_sqrt64(u64 x) { return int_sqrt(x); } -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, 2017-12-19 at 17:12 +0100, Peter Zijlstra wrote: > On Tue, Dec 19, 2017 at 08:09:53AM -0800, Joe Perches wrote: > > > > I suspect you need to define this as: > > > > #define int_sqrt64(x) ((u32)int_sqrt(x)) > > What's wrong with using C ? Duh. Nothing at all. > static inline u32 int_sqrt64(u64 x) > { > return int_sqrt(x); > } -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Thanks for suggestions and comments. Respinned v9 with them. On 19 December 2017 at 17:14, Joe Perches <joe@perches.com> wrote: > On Tue, 2017-12-19 at 17:12 +0100, Peter Zijlstra wrote: >> On Tue, Dec 19, 2017 at 08:09:53AM -0800, Joe Perches wrote: >> > >> > I suspect you need to define this as: >> > >> > #define int_sqrt64(x) ((u32)int_sqrt(x)) >> >> What's wrong with using C ? > > Duh. Nothing at all. > >> static inline u32 int_sqrt64(u64 x) >> { >> return int_sqrt(x); >> } -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 0ad4c3044cf9..f3bebd3a9213 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -459,6 +459,12 @@ extern int kernel_text_address(unsigned long addr); extern int func_ptr_is_kernel_text(void *ptr); unsigned long int_sqrt(unsigned long); +#if BITS_PER_LONG != 64 +#define int_sqrt64 _int_sqrt64 +u32 _int_sqrt64(u64 x); +#else +#define int_sqrt64 int_sqrt +#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 1ef4cc344977..84c77c934ec3 100644 --- a/lib/int_sqrt.c +++ b/lib/int_sqrt.c @@ -36,3 +36,35 @@ 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 << (64 - 2); + while (m != 0) { + b = y + m; + y >>= 1; + + if (x >= b) { + x -= b; + y += m; + } + m >>= 2; + } + + return y; +} +EXPORT_SYMBOL(_int_sqrt64); +#endif +
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 <cmo@melexis.com> --- include/linux/kernel.h | 6 ++++++ lib/int_sqrt.c | 32 ++++++++++++++++++++++++++++++++ 2 files changed, 38 insertions(+)