From: kernel test robot <lkp@intel.com>
To: oe-kbuild@lists.linux.dev
Cc: lkp@intel.com, Dan Carpenter <error27@gmail.com>
Subject: [linux-next:master 16319/17742] drivers/gpu/drm/xe/xe_hwmon.c:1344 xe_hwmon_temperature_decode() warn: impossible condition '(value > ((~0 >> 1))) => (s64min-s64max > s64max)'
Date: Tue, 20 Oct 2026 10:01:47 +0200 [thread overview]
Message-ID: <202610200910.SP0zWbkd-lkp@intel.com> (raw)
Unfiltered warning: this smatch report is sent as-is and has not been
reviewed for false positives, so please treat it with due skepticism.
BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
TO: Karthik Poosa <karthik.poosa@intel.com>
CC: Rodrigo Vivi <rodrigo.vivi@intel.com>
tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head: 3d229ce89862b8e82d71a9e11d6f840ca272a6d6
commit: 24ec15d646179a255f314e404343bf8e3200c9c0 [16319/17742] drm/xe/hwmon: Decode CRI temperature registers as IEEE-754
:::::: branch date: 14 hours ago
:::::: commit date: 5 days ago
config: x86_64-randconfig-r2202-20261019 (https://download.01.org/0day-ci/archive/20261020/202610200910.SP0zWbkd-lkp@intel.com/config)
compiler: clang version 22.1.8 (https://github.com/llvm/llvm-project ca7933e47d3a3451d81e72ac174dcb5aa28b59d1)
rustc: rustc 1.96.0 (ac68faa20 2026-05-25)
smatch: v0.5.0-9187-g5189e3fb
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202610200910.SP0zWbkd-lkp@intel.com/
smatch warnings:
drivers/gpu/drm/xe/xe_hwmon.c:1344 xe_hwmon_temperature_decode() warn: impossible condition '(value > ((~0 >> 1))) => (s64min-s64max > s64max)'
vim +1344 drivers/gpu/drm/xe/xe_hwmon.c
24ec15d646179a Karthik Poosa 2026-10-15 1296
24ec15d646179a Karthik Poosa 2026-10-15 1297 /**
24ec15d646179a Karthik Poosa 2026-10-15 1298 * xe_hwmon_temperature_decode - Decode an IEEE-754 temperature register value
24ec15d646179a Karthik Poosa 2026-10-15 1299 * @reg_val: The raw register value to decode
24ec15d646179a Karthik Poosa 2026-10-15 1300 * @temperature: Pointer to store the decoded temperature in millidegrees Celsius.
24ec15d646179a Karthik Poosa 2026-10-15 1301 *
24ec15d646179a Karthik Poosa 2026-10-15 1302 * IEEE-754 single-precision format:
24ec15d646179a Karthik Poosa 2026-10-15 1303 *
24ec15d646179a Karthik Poosa 2026-10-15 1304 * 31 30 23 22 0
24ec15d646179a Karthik Poosa 2026-10-15 1305 * +--+-----------------------------+----------------------------+
24ec15d646179a Karthik Poosa 2026-10-15 1306 * | S| exponent | fraction |
24ec15d646179a Karthik Poosa 2026-10-15 1307 * +--+-----------------------------+----------------------------+
24ec15d646179a Karthik Poosa 2026-10-15 1308 *
24ec15d646179a Karthik Poosa 2026-10-15 1309 * value = (-1)^S * 1.fraction * 2^(exponent - 127)
24ec15d646179a Karthik Poosa 2026-10-15 1310 *
24ec15d646179a Karthik Poosa 2026-10-15 1311 * Return: 0 on success or an error if @reg_val is non-finite or cannot be
24ec15d646179a Karthik Poosa 2026-10-15 1312 * represented in millidegrees Celsius.
24ec15d646179a Karthik Poosa 2026-10-15 1313 */
24ec15d646179a Karthik Poosa 2026-10-15 1314 static int xe_hwmon_temperature_decode(u32 reg_val, long *temperature)
24ec15d646179a Karthik Poosa 2026-10-15 1315 {
24ec15d646179a Karthik Poosa 2026-10-15 1316 u32 exponent = REG_FIELD_GET(IEEE754_EXP_MASK, reg_val);
24ec15d646179a Karthik Poosa 2026-10-15 1317 u32 mantissa = REG_FIELD_GET(IEEE754_MANTISSA_MASK, reg_val);
24ec15d646179a Karthik Poosa 2026-10-15 1318 s64 value;
24ec15d646179a Karthik Poosa 2026-10-15 1319 int shift;
24ec15d646179a Karthik Poosa 2026-10-15 1320
24ec15d646179a Karthik Poosa 2026-10-15 1321 /* Exponent 0xff encodes infinity or NaN. */
24ec15d646179a Karthik Poosa 2026-10-15 1322 if (exponent == IEEE754_EXP_SPECIAL)
24ec15d646179a Karthik Poosa 2026-10-15 1323 return -EINVAL;
24ec15d646179a Karthik Poosa 2026-10-15 1324
24ec15d646179a Karthik Poosa 2026-10-15 1325 /* Subnormal values are smaller than one millidegree Celsius. */
24ec15d646179a Karthik Poosa 2026-10-15 1326 if (!exponent) {
24ec15d646179a Karthik Poosa 2026-10-15 1327 *temperature = 0;
24ec15d646179a Karthik Poosa 2026-10-15 1328 return 0;
24ec15d646179a Karthik Poosa 2026-10-15 1329 }
24ec15d646179a Karthik Poosa 2026-10-15 1330
24ec15d646179a Karthik Poosa 2026-10-15 1331 value = (s64)(mantissa | BIT(IEEE754_MANTISSA_BITS)) * MILLIDEGREE_PER_DEGREE;
24ec15d646179a Karthik Poosa 2026-10-15 1332 shift = exponent - (IEEE754_EXP_BIAS + IEEE754_MANTISSA_BITS);
24ec15d646179a Karthik Poosa 2026-10-15 1333 if (shift >= 0) {
24ec15d646179a Karthik Poosa 2026-10-15 1334 if (shift >= BITS_PER_LONG || value > (LONG_MAX >> shift))
24ec15d646179a Karthik Poosa 2026-10-15 1335 return -ERANGE;
24ec15d646179a Karthik Poosa 2026-10-15 1336 value <<= shift;
24ec15d646179a Karthik Poosa 2026-10-15 1337 } else if (shift > -64) {
24ec15d646179a Karthik Poosa 2026-10-15 1338 value >>= -shift;
24ec15d646179a Karthik Poosa 2026-10-15 1339 } else {
24ec15d646179a Karthik Poosa 2026-10-15 1340 value = 0;
24ec15d646179a Karthik Poosa 2026-10-15 1341 }
24ec15d646179a Karthik Poosa 2026-10-15 1342
24ec15d646179a Karthik Poosa 2026-10-15 1343 /* Ensure the magnitude fits in long, which is 32-bit on some arches. */
24ec15d646179a Karthik Poosa 2026-10-15 @1344 if (value > LONG_MAX)
24ec15d646179a Karthik Poosa 2026-10-15 1345 return -ERANGE;
24ec15d646179a Karthik Poosa 2026-10-15 1346
24ec15d646179a Karthik Poosa 2026-10-15 1347 if (reg_val & IEEE754_SIGN)
24ec15d646179a Karthik Poosa 2026-10-15 1348 value = -value;
24ec15d646179a Karthik Poosa 2026-10-15 1349
24ec15d646179a Karthik Poosa 2026-10-15 1350 *temperature = value;
24ec15d646179a Karthik Poosa 2026-10-15 1351 return 0;
24ec15d646179a Karthik Poosa 2026-10-15 1352 }
24ec15d646179a Karthik Poosa 2026-10-15 1353
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
reply other threads:[~2026-10-20 8:02 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=202610200910.SP0zWbkd-lkp@intel.com \
--to=lkp@intel.com \
--cc=error27@gmail.com \
--cc=oe-kbuild@lists.linux.dev \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.