Re: [PATCH] drm/xe/hwmon: Store mailbox temperature data as bytes

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

On 26-10-2026 04:47 pm, Poosa, Karthik wrote:
>
> On 23-10-2026 16:06, Mallesh Koujalagi wrote:
>> Store pcode mailbox temperature data directly in the byte array
>> using put_unaligned_le32() instead of accessing it through
>> different views of the same storage.
>>
>> This keeps the layout unchanged and makes the data access
>> consistent and endian-safe.
>
> 1. Is this patch addressing any issue reported by a static analysis tool?
>
Yes, it's reported by static analysis tool.
> 2. Given that |cpu_to_le3()| already handles endianness, do we still 
> need this change?

Yes, cpu_to_le32() already handles endianness correctly. The main reason 
for this change is not

to fix an endianness issue, however to address the static analysis 
warning about inconsistent union access.

The code writes data through temp.dword[] and later reads it through 
temp.value[], which was flagged as

inconsistent access.

To avoid that used put_unaligned_le32 writes directly into the byte 
array that is later

read, making the access pattern consistent.


Thanks,

-/Mallesh

>
>>
>> Fixes: ca6e33701de8 ("drm/xe/hwmon: Fix thermal sensor data handling")
>> Signed-off-by: Mallesh Koujalagi <mallesh.koujalagi@intel.com>
>> ---
>>   drivers/gpu/drm/xe/xe_hwmon.c | 15 ++++++++-------
>>   1 file changed, 8 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_hwmon.c 
>> b/drivers/gpu/drm/xe/xe_hwmon.c
>> index 42acfeb8818c..7bb1223dc30b 100644
>> --- a/drivers/gpu/drm/xe/xe_hwmon.c
>> +++ b/drivers/gpu/drm/xe/xe_hwmon.c
>> @@ -7,6 +7,7 @@
>>   #include <linux/hwmon.h>
>>   #include <linux/jiffies.h>
>>   #include <linux/types.h>
>> +#include <linux/unaligned.h>
>>   #include <linux/units.h>
>>     #include <drm/drm_managed.h>
>> @@ -165,12 +166,12 @@ struct xe_hwmon_thermal_info {
>>       bool available[CHANNEL_MAX];
>>       /** @msu_mask: VRAM subsystem enable mask read from MMIO */
>>       u32 msu_mask;
>> -    union {
>> -        /** @value: per-sensor raw mailbox temperature; bit7=sign, 
>> bits6:0=magnitude */
>> -        u8 value[U8_MAX + 1];
>> -        /** @dword: sensor values as little-endian dwords, 
>> u32-aligned for pcode reads */
>> -        __le32 dword[DIV_ROUND_UP(U8_MAX + 1, sizeof(u32))];
>> -    };
>> +    /**
>> +     * @value: per-sensor raw mailbox temperature; bit7=sign, 
>> bits6:0=magnitude.
>> +     * Written one dword at a time via put_unaligned_le32() to
> Written -> Write
>> +     * avoid inconsistent union access between dword and byte views.
>> +     */
>> +    u8 value[U8_MAX + 1];
>>       /** @vram_label: vram label names, dynamically allocated based 
>> on vram_count */
>>       char (*vram_label)[MAX_LABEL_SIZE];
>>   };
>> @@ -995,7 +996,7 @@ static int get_mc_temp(struct xe_hwmon *hwmon, 
>> long *val)
>>           if (ret)
>>               return ret;
>>           drm_dbg(&hwmon->xe->drm, "thermal data for group %d val 
>> 0x%x\n", i, data);
>> -        hwmon->temp.dword[i] = cpu_to_le32(data);
>> +        put_unaligned_le32(data, &hwmon->temp.value[i * sizeof(u32)]);
>>       }
>>         for (i = start; i < end; i++) {