Re: [PATCH v2] drm/xe/hwmon: Use overflows_type() for temperature range check

["Mallesh, Koujalagi" <mallesh.koujalagi@intel.com>]

On 26-10-2026 05:04 pm, Poosa, Karthik wrote:
>
> On 23-10-2026 20:06, Mallesh Koujalagi wrote:
>> The temperature value is calculated as an s64 before being stored
>> in a long. Check whether the value fits in the target type using
>> overflows_type() instead of comparing against LONG_MAX directly.
>>
>> This keeps the overflow check correct on both 32-bit and 64-bit
>> systems and avoids architecture-specific handling.
>>
>> Fixes: 24ec15d64617 ("drm/xe/hwmon: Decode CRI temperature registers 
>> as IEEE-754")
>> Signed-off-by: Mallesh Koujalagi <mallesh.koujalagi@intel.com>
>> ---
>> v2:
>> - Use overflows_type(), instead of #ifdef. (Jani)
>> ---
>>   drivers/gpu/drm/xe/xe_hwmon.c | 5 +++--
>>   1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_hwmon.c 
>> b/drivers/gpu/drm/xe/xe_hwmon.c
>> index 42acfeb8818c..515b288f18e5 100644
>> --- a/drivers/gpu/drm/xe/xe_hwmon.c
>> +++ b/drivers/gpu/drm/xe/xe_hwmon.c
>> @@ -6,6 +6,7 @@
>>   #include <linux/hwmon-sysfs.h>
>>   #include <linux/hwmon.h>
>>   #include <linux/jiffies.h>
>> +#include <linux/overflow.h>
>>   #include <linux/types.h>
>>   #include <linux/units.h>
>>   @@ -1322,8 +1323,8 @@ static int xe_hwmon_temperature_decode(u32 
>> reg_val, long *temperature)
>>           value = 0;
>>       }
>>   -    /* Ensure the magnitude fits in long, which is 32-bit on some 
>> arches. */
>> -    if (value > LONG_MAX)
>> +    /* Ensure the decoded value fits in a long. */
>> +    if (overflows_type(value, *temperature))
> Is this change addressing an issue reported by a static analysis tool ?
Yes, it's reported by a static analysis tool.
>
> |LONG_MAX| already reflects the platform-specific size of |long|, so 
> is this still needed ?
>
On 64 bit arch, where long and s64 are the same width, however (value > 
LONG_MAX)

is always false because LONG_MAX is 9223372036854775807LL /* (long)(~0UL 
 >> 1) */,

As a result,  "return -ERANGE" path is considered dead code and gets 
flagged.


Using overflows_type() makes the overflow check explicit across 32-bit 
and 64-bit arch and avoid flagging by

static analysis tool without changing the behavior.


Thanks,

-/Mallesh

>>           return -ERANGE;
>>         if (reg_val & IEEE754_SIGN)