Re: [PATCH] iio: use div64_u64() instead of do_div()

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Le 13/02/2022 à 19:50, Christophe JAILLET a écrit :
Le 13/02/2022 à 18:59, Jonathan Cameron a écrit :
On Wed,  9 Feb 2022 00:37:53 -0800
Qing Wang <wangqing-DGpbCiVdSXo@xxxxxxxxxxxxxxxx> wrote:

From: Wang Qing <wangqing-DGpbCiVdSXo@xxxxxxxxxxxxxxxx>

do_div() does a 64-by-32 division.
When the divisor is u64, do_div() truncates it to 32 bits, this means it
can test non-zero and be truncated to zero for division.

fix do_div.cocci warning:
do_div() does a 64-by-32 division, please consider using div64_u64 instead.

Signed-off-by: Wang Qing <wangqing-DGpbCiVdSXo@xxxxxxxxxxxxxxxx>
These look correct to me.  Jyoti, please could give these a sanity check?


This is wrong.

See [1].

CJ

[1]: https://lore.kernel.org/linux-kernel/20211117112559.jix3hmx7uwqmuryg-bIcnvbaLZ9MEGnE8C9+IrQ@xxxxxxxxxxxxxxxx/

Broken link, sorry:

[1] https://lore.kernel.org/linux-kernel/20211117112559.jix3hmx7uwqmuryg@xxxxxxxxxxxxxx/



Thanks,

Jonathan

---
  drivers/iio/common/scmi_sensors/scmi_iio.c | 10 +++++-----
  1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/common/scmi_sensors/scmi_iio.c b/drivers/iio/common/scmi_sensors/scmi_iio.c
index d538bf3..d6df5da
--- a/drivers/iio/common/scmi_sensors/scmi_iio.c
+++ b/drivers/iio/common/scmi_sensors/scmi_iio.c
@@ -160,7 +160,7 @@ static int scmi_iio_set_odr_val(struct iio_dev *iio_dev, int val, int val2)
      mult = scnprintf(buf, sizeof(buf), "%llu", sf) - 1;
      sec = int_pow(10, mult) * UHZ_PER_HZ;
-    do_div(sec, uHz);
+    div64_u64(sec, uHz);
      if (sec == 0) {
          dev_err(&iio_dev->dev,
              "Trying to set invalid sensor update value for sensor %s",
@@ -237,10 +237,10 @@ static void convert_ns_to_freq(u64 interval_ns, u64 *hz, u64 *uhz)
      u64 rem, freq;
      freq = NSEC_PER_SEC;
-    rem = do_div(freq, interval_ns);
+    rem = div64_u64(freq, interval_ns);
      *hz = freq;
      *uhz = rem * 1000000UL;
-    do_div(*uhz, interval_ns);
+    div64_u64(*uhz, interval_ns);
  }
  static int scmi_iio_get_odr_val(struct iio_dev *iio_dev, int *val, int *val2) @@ -266,7 +266,7 @@ static int scmi_iio_get_odr_val(struct iio_dev *iio_dev, int *val, int *val2)
      mult = SCMI_SENS_CFG_GET_UPDATE_EXP(sensor_config);
      if (mult < 0) {
          sensor_interval_mult = int_pow(10, abs(mult));
-        do_div(sensor_update_interval, sensor_interval_mult);
+        div64_u64(sensor_update_interval, sensor_interval_mult);
      } else {
          sensor_interval_mult = int_pow(10, mult);
          sensor_update_interval =
@@ -500,7 +500,7 @@ static u64 scmi_iio_convert_interval_to_ns(u32 val)
      mult = SCMI_SENS_INTVL_GET_EXP(val);
      if (mult < 0) {
          sensor_interval_mult = int_pow(10, abs(mult));
-        do_div(sensor_update_interval, sensor_interval_mult);
+        div64_u64(sensor_update_interval, sensor_interval_mult);
      } else {
          sensor_interval_mult = int_pow(10, mult);
          sensor_update_interval =








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