[PATCH] staging: iio: Use div64_ul instead of do_div

[PATCH] staging: iio: Use div64_ul instead of do_div

[Kang Minchul]

Using div64_ul instead of do_div (64-by-32 division) is more
recommended by coccicheck because this can avoid potential truncation.

So this commit changes do_div to div64_ul and
remove coccicheck warnings.

Signed-off-by: Kang Minchul <tegongkang@gmail.com>
---
 drivers/staging/iio/frequency/ad9832.c          | 2 +-
 drivers/staging/iio/frequency/ad9834.c          | 2 +-
 drivers/staging/iio/impedance-analyzer/ad5933.c | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/iio/frequency/ad9832.c b/drivers/staging/iio/frequency/ad9832.c
index 6f9eebd6c7ee..cd038480f63c 100644
--- a/drivers/staging/iio/frequency/ad9832.c
+++ b/drivers/staging/iio/frequency/ad9832.c
@@ -122,7 +122,7 @@ static unsigned long ad9832_calc_freqreg(unsigned long mclk, unsigned long fout)
 {
 	unsigned long long freqreg = (u64)fout *
 				     (u64)((u64)1L << AD9832_FREQ_BITS);
-	do_div(freqreg, mclk);
+	freqreg = div64_ul(freqreg, mclk);
 	return freqreg;
 }
 
diff --git a/drivers/staging/iio/frequency/ad9834.c b/drivers/staging/iio/frequency/ad9834.c
index 2b4267a87e65..cfe933ef40d0 100644
--- a/drivers/staging/iio/frequency/ad9834.c
+++ b/drivers/staging/iio/frequency/ad9834.c
@@ -102,7 +102,7 @@ static unsigned int ad9834_calc_freqreg(unsigned long mclk, unsigned long fout)
 {
 	unsigned long long freqreg = (u64)fout * (u64)BIT(AD9834_FREQ_BITS);
 
-	do_div(freqreg, mclk);
+	freqreg = div64_ul(freqreg, mclk);
 	return freqreg;
 }
 
diff --git a/drivers/staging/iio/impedance-analyzer/ad5933.c b/drivers/staging/iio/impedance-analyzer/ad5933.c
index f177b20f0f2d..730bb31a20d8 100644
--- a/drivers/staging/iio/impedance-analyzer/ad5933.c
+++ b/drivers/staging/iio/impedance-analyzer/ad5933.c
@@ -196,7 +196,7 @@ static int ad5933_set_freq(struct ad5933_state *st,
 	} dat;
 
 	freqreg = (u64)freq * (u64)(1 << 27);
-	do_div(freqreg, st->mclk_hz / 4);
+	freqreg = div64_ul(freqreg, st->mclk_hz / 4);
 
 	switch (reg) {
 	case AD5933_REG_FREQ_START:
-- 
2.34.1

Re: [PATCH] staging: iio: Use div64_ul instead of do_div

[Greg Kroah-Hartman]

On Wed, Oct 19, 2022 at 02:38:29PM +0900, Kang Minchul wrote:
> Using div64_ul instead of do_div (64-by-32 division) is more
> recommended by coccicheck because this can avoid potential truncation.
> 
> So this commit changes do_div to div64_ul and
> remove coccicheck warnings.
> 
> Signed-off-by: Kang Minchul <tegongkang@gmail.com>
> ---
>  drivers/staging/iio/frequency/ad9832.c          | 2 +-
>  drivers/staging/iio/frequency/ad9834.c          | 2 +-
>  drivers/staging/iio/impedance-analyzer/ad5933.c | 2 +-
>  3 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/iio/frequency/ad9832.c b/drivers/staging/iio/frequency/ad9832.c
> index 6f9eebd6c7ee..cd038480f63c 100644
> --- a/drivers/staging/iio/frequency/ad9832.c
> +++ b/drivers/staging/iio/frequency/ad9832.c
> @@ -122,7 +122,7 @@ static unsigned long ad9832_calc_freqreg(unsigned long mclk, unsigned long fout)
>  {
>  	unsigned long long freqreg = (u64)fout *
>  				     (u64)((u64)1L << AD9832_FREQ_BITS);
> -	do_div(freqreg, mclk);
> +	freqreg = div64_ul(freqreg, mclk);

I think the original code here is correct, no need for a change, unless
you have the hardware to test this out and can verify it all still works
identically.

thanks,

greg k-h