| Message ID | 20180213165258.GA12967@embeddedor.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, 13 Feb 2018 10:52:58 -0600 "Gustavo A. R. Silva" <garsilva@embeddedor.com> wrote: > Add suffix ULL to constant 1000 in order to give the compiler complete > information about the proper arithmetic to use. Notice that this > constant is used in a context that expects an expression of type > u64 (64 bits, unsigned). > > The expression 1000 * sampling_us is currently being evaluated > using 32-bit arithmetic. > > Addresses-Coverity-ID: 1463793 > Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com> I've been trying to figure out if this matters in reality. i.e. whether or not sampling_us is big enough for us to need 64 bit multiplication. It's equal to the output for the macro SAMPLING_PERIOD(c) (int_time_vbus + int_time_vshunt) * avg So taking max values (8244 + 68100) * 1024 = 78176256 Then * 1000 which brings it well into the > 32bit range. So the next question is when was this introduced. I guess it was Stefan's recent patch but haven't checked yet... Marc / Stephan, could you check if we are correct in thinking this is a real bug rather than just a numerical oddity? Thanks, Jonathan > --- > drivers/iio/adc/ina2xx-adc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/iio/adc/ina2xx-adc.c b/drivers/iio/adc/ina2xx-adc.c > index 0635a79..8649700 100644 > --- a/drivers/iio/adc/ina2xx-adc.c > +++ b/drivers/iio/adc/ina2xx-adc.c > @@ -810,7 +810,7 @@ static int ina2xx_capture_thread(void *data) > * multiple times, i.e. samples are dropped. > */ > do { > - timespec64_add_ns(&next, 1000 * sampling_us); > + timespec64_add_ns(&next, 1000ULL * sampling_us); > delta = timespec64_sub(next, now); > delay_us = div_s64(timespec64_to_ns(&delta), 1000); > } while (delay_us <= 0); -- 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/drivers/iio/adc/ina2xx-adc.c b/drivers/iio/adc/ina2xx-adc.c index 0635a79..8649700 100644 --- a/drivers/iio/adc/ina2xx-adc.c +++ b/drivers/iio/adc/ina2xx-adc.c @@ -810,7 +810,7 @@ static int ina2xx_capture_thread(void *data) * multiple times, i.e. samples are dropped. */ do { - timespec64_add_ns(&next, 1000 * sampling_us); + timespec64_add_ns(&next, 1000ULL * sampling_us); delta = timespec64_sub(next, now); delay_us = div_s64(timespec64_to_ns(&delta), 1000); } while (delay_us <= 0);
Add suffix ULL to constant 1000 in order to give the compiler complete information about the proper arithmetic to use. Notice that this constant is used in a context that expects an expression of type u64 (64 bits, unsigned). The expression 1000 * sampling_us is currently being evaluated using 32-bit arithmetic. Addresses-Coverity-ID: 1463793 Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com> --- drivers/iio/adc/ina2xx-adc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)