This commit removes warning generated by cocci as follows:
do_div() does a 64-by-32 division, please consider using div64_u64 instead.
Using div64_u64 instead of do_div can avoid potential truncation.
Signed-off-by: Kang Minchul <[email protected]>
---
drivers/staging/pi433/rf69.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/staging/pi433/rf69.c b/drivers/staging/pi433/rf69.c
index 8c7fab6a46bb..683dd94489f9 100644
--- a/drivers/staging/pi433/rf69.c
+++ b/drivers/staging/pi433/rf69.c
@@ -252,11 +252,11 @@ int rf69_set_deviation(struct spi_device *spi, u32 deviation)
// calculat f step
f_step = F_OSC * factor;
- do_div(f_step, 524288); // 524288 = 2^19
+ div64_u64(f_step, 524288); // 524288 = 2^19
// calculate register settings
f_reg = deviation * factor;
- do_div(f_reg, f_step);
+ div64_u64(f_reg, f_step);
msb = (f_reg & 0xff00) >> 8;
lsb = (f_reg & 0xff);
@@ -291,7 +291,7 @@ int rf69_set_frequency(struct spi_device *spi, u32 frequency)
// calculat f step
f_step = F_OSC * factor;
- do_div(f_step, 524288); // 524288 = 2^19
+ div64_u64(f_step, 524288); // 524288 = 2^19
// check input value
f_max = div_u64(f_step * 8388608, factor);
@@ -302,7 +302,7 @@ int rf69_set_frequency(struct spi_device *spi, u32 frequency)
// calculate reg settings
f_reg = frequency * factor;
- do_div(f_reg, f_step);
+ div64_u64(f_reg, f_step);
msb = (f_reg & 0xff0000) >> 16;
mid = (f_reg & 0xff00) >> 8;
--
2.34.1
From: Kang Minchul
> Sent: 19 October 2022 10:40
>
> This commit removes warning generated by cocci as follows:
>
> do_div() does a 64-by-32 division, please consider using div64_u64 instead.
>
> Using div64_u64 instead of do_div can avoid potential truncation.
Cocci is lying to you.
do_div() exists because a 64 by 32 bit divide is significantly
faster than a 64 by 64 divide.
This is particularly true on 32bit cpu, but is also true on
Intel x86_64 bit cpu.
So unless the result might actually be larger than 32 bits
(which requires code analysis) then do_div() is correct.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
2022년 10월 19일 (수) 오후 7:31, David Laight <[email protected]>님이 작성:
>
> From: Kang Minchul
> > Sent: 19 October 2022 10:40
> >
> > This commit removes warning generated by cocci as follows:
> >
> > do_div() does a 64-by-32 division, please consider using div64_u64 instead.
> >
> > Using div64_u64 instead of do_div can avoid potential truncation.
>
> Cocci is lying to you.
>
> do_div() exists because a 64 by 32 bit divide is significantly
> faster than a 64 by 64 divide.
> This is particularly true on 32bit cpu, but is also true on
> Intel x86_64 bit cpu.
I guess I have missed that point,
Thanks for your feedback!
Kang Minchul