From: Hans de Goede <hdegoede@redhat.com>
To: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
Colin Ian King <colin.king@canonical.com>,
Jani Nikula <jani.nikula@linux.intel.com>,
Mark Gross <mgross@linux.intel.com>,
Rodrigo Vivi <rodrigo.vivi@intel.com>,
Jesse Barnes <jsbarnes@google.com>
Cc: intel-gfx@lists.freedesktop.org,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
platform-driver-x86@vger.kernel.org
Subject: Re: Computation of return value being discarded in get_cpu_power() in drivers/platform/x86/intel_ips.c
Date: Thu, 10 Jun 2021 17:55:19 +0200 [thread overview]
Message-ID: <7e13032d-1472-9c50-1dba-9dcebc76729f@redhat.com> (raw)
In-Reply-To: <162332615476.15946.17135355064135638083@jlahtine-mobl.ger.corp.intel.com>
Hi,
On 6/10/21 1:55 PM, Joonas Lahtinen wrote:
> (Address for Hans was corrupt in previous message, which confused my mail
> client. Sorry for duplicate message, the other is without From: field).
>
> + Jesse
>
> Quoting Colin Ian King (2021-06-09 14:50:07)
>> 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.
This has already been fixed (yesterday actually) in linux-next:
https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/commit/?h=for-next&id=13c3b4f76073d73dd81e418295902676153f6cb5
Regards,
Hans
prev parent reply other threads:[~2021-06-10 15:55 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-09 11:50 Computation of return value being discarded in get_cpu_power() in drivers/platform/x86/intel_ips.c Colin Ian King
2021-06-10 11:51 ` joonas.lahtinen
2021-06-10 11:55 ` Joonas Lahtinen
2021-06-10 15:40 ` Jesse Barnes
2021-06-10 15:43 ` Jesse Barnes
2021-06-10 15:55 ` Hans de Goede [this message]
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