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SubjectComputation of return value being discarded in get_cpu_power() in drivers/platform/x86/intel_ips.c
Date
Hi,

I was reviewing some old unassigned variable warnings from static
analysis by Coverity and found an issue introduced with the following
commit:

commit aa7ffc01d254c91a36bf854d57a14049c6134c72
Author: Jesse Barnes <jbarnes@virtuousgeek.org>
Date: Fri May 14 15:41:14 2010 -0700

x86 platform driver: intelligent power sharing driver

The analysis is as follows:

drivers/platform/x86/intel_ips.c

871 static u32 get_cpu_power(struct ips_driver *ips, u32 *last, int period)
872 {
873 u32 val;
874 u32 ret;
875
876 /*
877 * CEC is in joules/65535. Take difference over time to
878 * get watts.
879 */
880 val = thm_readl(THM_CEC);
881
882 /* period is in ms and we want mW */
883 ret = (((val - *last) * 1000) / period);

Unused value (UNUSED_VALUE)
assigned_value: Assigning value from ret * 1000U / 65535U to ret here,
but that stored value is not used.

884 ret = (ret * 1000) / 65535;
885 *last = val;
886
887 return 0;
888 }

I'm really not sure why ret is being calculated on lines 883,884 and not
being used. Should that be *last = ret on line 885? Looks suspect anyhow.

Colin


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