Re: [RFC PATCH v2 1/1] iio/scmi: Adding support for IIO SCMI Based Sensors

Lars-Peter Clausen
2020-12-30T16:10:44Z

On 12/30/20 2:41 PM, Jonathan Cameron wrote:
> On Thu, 24 Dec 2020 03:19:21 +0000
> Jyoti Bhayana <jbhayana@google.com> wrote:
>
>> + /*
>> + * The seconds field in the sensor interval in SCMI is 16 bits long
>> + * Therefore seconds = 1/Hz <= 0xFFFF. As floating point calculations are
>> + * discouraged in the kernel driver code, to calculate the scale factor (sf)
>> + * (1* 1000000 * sf)/uHz <= 0xFFFF. Therefore, sf <= (uHz * 0xFFFF)/1000000
>> + * To calculate the multiplier,we convert the sf into char string and
>> + * count the number of characters
>> + */
>> +
>> + mult = scnprintf(buf, 32, "%llu", ((u64)uHz * 0xFFFF) / UHZ_PER_HZ) - 1;
> use sizeof(buf) instead of having 32 again.
>
Since this is just interested in the number of characters and not the
string itself I believe it is possible to just call sprintf with NULL
instead of a buffer. It will then still return the number of characters,
but not print anything.

But maybe providing a ilog10() helper is the better approach.