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

["Poosa, Karthik" <karthik.poosa@intel.com>]

On 26-10-2026 18:06, Mallesh, Koujalagi wrote:
>
> 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
okay,
Reviewed-by: Karthik Poosa <karthik.poosa@intel.com>
>
>>>           return -ERANGE;
>>>         if (reg_val & IEEE754_SIGN)