tree: git://git.lwn.net/linux-2.6 docs-next head: f9bbc12ccb35ac8b3fa01cec1a19cb523a7707c7 commit: f9bbc12ccb35ac8b3fa01cec1a19cb523a7707c7 [127/127] scripts: kernel-doc: improve parsing for kernel-doc comments syntax config: arc-allyesconfig (attached as .config) compiler: arceb-elf-gcc (GCC) 9.3.0 reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross git remote add lwn git://git.lwn.net/linux-2.6 git fetch --no-tags lwn docs-next git checkout f9bbc12ccb35ac8b3fa01cec1a19cb523a7707c7 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross W=1 ARCH=arc If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): sound/soc/codecs/nau8825.c:298: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst * Ramp up the headphone volume change gradually to target level. sound/soc/codecs/nau8825.c:411: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst * computes cross talk suppression sidetone gain. vim +358 sound/soc/codecs/nau8825.c b50455fab459b0b John Hsu 2016-06-07 296 b50455fab459b0b John Hsu 2016-06-07 297 /** b50455fab459b0b John Hsu 2016-06-07 @298 * Ramp up the headphone volume change gradually to target level. b50455fab459b0b John Hsu 2016-06-07 299 * b50455fab459b0b John Hsu 2016-06-07 300 * @nau8825: component to register the codec private data with b50455fab459b0b John Hsu 2016-06-07 301 * @vol_from: the volume to start up b50455fab459b0b John Hsu 2016-06-07 302 * @vol_to: the target volume b50455fab459b0b John Hsu 2016-06-07 303 * @step: the volume span to move on b50455fab459b0b John Hsu 2016-06-07 304 * b50455fab459b0b John Hsu 2016-06-07 305 * The headphone volume is from 0dB to minimum -54dB and -1dB per step. b50455fab459b0b John Hsu 2016-06-07 306 * If the volume changes sharp, there is a pop noise heard in headphone. We b50455fab459b0b John Hsu 2016-06-07 307 * provide the function to ramp up the volume up or down by delaying 10ms b50455fab459b0b John Hsu 2016-06-07 308 * per step. b50455fab459b0b John Hsu 2016-06-07 309 */ b50455fab459b0b John Hsu 2016-06-07 310 static void nau8825_hpvol_ramp(struct nau8825 *nau8825, b50455fab459b0b John Hsu 2016-06-07 311 unsigned int vol_from, unsigned int vol_to, unsigned int step) b50455fab459b0b John Hsu 2016-06-07 312 { b50455fab459b0b John Hsu 2016-06-07 313 unsigned int value, volume, ramp_up, from, to; b50455fab459b0b John Hsu 2016-06-07 314 b50455fab459b0b John Hsu 2016-06-07 315 if (vol_from == vol_to || step == 0) { b50455fab459b0b John Hsu 2016-06-07 316 return; b50455fab459b0b John Hsu 2016-06-07 317 } else if (vol_from < vol_to) { b50455fab459b0b John Hsu 2016-06-07 318 ramp_up = true; b50455fab459b0b John Hsu 2016-06-07 319 from = vol_from; b50455fab459b0b John Hsu 2016-06-07 320 to = vol_to; b50455fab459b0b John Hsu 2016-06-07 321 } else { b50455fab459b0b John Hsu 2016-06-07 322 ramp_up = false; b50455fab459b0b John Hsu 2016-06-07 323 from = vol_to; b50455fab459b0b John Hsu 2016-06-07 324 to = vol_from; b50455fab459b0b John Hsu 2016-06-07 325 } b50455fab459b0b John Hsu 2016-06-07 326 /* only handle volume from 0dB to minimum -54dB */ b50455fab459b0b John Hsu 2016-06-07 327 if (to > NAU8825_HP_VOL_MIN) b50455fab459b0b John Hsu 2016-06-07 328 to = NAU8825_HP_VOL_MIN; b50455fab459b0b John Hsu 2016-06-07 329 b50455fab459b0b John Hsu 2016-06-07 330 for (volume = from; volume < to; volume += step) { b50455fab459b0b John Hsu 2016-06-07 331 if (ramp_up) b50455fab459b0b John Hsu 2016-06-07 332 value = volume; b50455fab459b0b John Hsu 2016-06-07 333 else b50455fab459b0b John Hsu 2016-06-07 334 value = to - volume + from; b50455fab459b0b John Hsu 2016-06-07 335 regmap_update_bits(nau8825->regmap, NAU8825_REG_HSVOL_CTRL, b50455fab459b0b John Hsu 2016-06-07 336 NAU8825_HPL_VOL_MASK | NAU8825_HPR_VOL_MASK, b50455fab459b0b John Hsu 2016-06-07 337 (value << NAU8825_HPL_VOL_SFT) | value); b50455fab459b0b John Hsu 2016-06-07 338 usleep_range(10000, 10500); b50455fab459b0b John Hsu 2016-06-07 339 } b50455fab459b0b John Hsu 2016-06-07 340 if (ramp_up) b50455fab459b0b John Hsu 2016-06-07 341 value = to; b50455fab459b0b John Hsu 2016-06-07 342 else b50455fab459b0b John Hsu 2016-06-07 343 value = from; b50455fab459b0b John Hsu 2016-06-07 344 regmap_update_bits(nau8825->regmap, NAU8825_REG_HSVOL_CTRL, b50455fab459b0b John Hsu 2016-06-07 345 NAU8825_HPL_VOL_MASK | NAU8825_HPR_VOL_MASK, b50455fab459b0b John Hsu 2016-06-07 346 (value << NAU8825_HPL_VOL_SFT) | value); b50455fab459b0b John Hsu 2016-06-07 347 } b50455fab459b0b John Hsu 2016-06-07 348 b50455fab459b0b John Hsu 2016-06-07 349 /** b50455fab459b0b John Hsu 2016-06-07 350 * Computes log10 of a value; the result is round off to 3 decimal. This func- b50455fab459b0b John Hsu 2016-06-07 351 * tion takes reference to dvb-math. The source code locates as the following. b50455fab459b0b John Hsu 2016-06-07 352 * Linux/drivers/media/dvb-core/dvb_math.c dc22a4093f5d297 Pierre-Louis Bossart 2019-01-04 353 * @value: input for log10 b50455fab459b0b John Hsu 2016-06-07 354 * b50455fab459b0b John Hsu 2016-06-07 355 * return log10(value) * 1000 b50455fab459b0b John Hsu 2016-06-07 356 */ b50455fab459b0b John Hsu 2016-06-07 357 static u32 nau8825_intlog10_dec3(u32 value) b50455fab459b0b John Hsu 2016-06-07 @358 { b50455fab459b0b John Hsu 2016-06-07 359 u32 msb, logentry, significand, interpolation, log10val; b50455fab459b0b John Hsu 2016-06-07 360 u64 log2val; b50455fab459b0b John Hsu 2016-06-07 361 b50455fab459b0b John Hsu 2016-06-07 362 /* first detect the msb (count begins at 0) */ b50455fab459b0b John Hsu 2016-06-07 363 msb = fls(value) - 1; b50455fab459b0b John Hsu 2016-06-07 364 /** b50455fab459b0b John Hsu 2016-06-07 365 * now we use a logtable after the following method: b50455fab459b0b John Hsu 2016-06-07 366 * b50455fab459b0b John Hsu 2016-06-07 367 * log2(2^x * y) * 2^24 = x * 2^24 + log2(y) * 2^24 b50455fab459b0b John Hsu 2016-06-07 368 * where x = msb and therefore 1 <= y < 2 b50455fab459b0b John Hsu 2016-06-07 369 * first y is determined by shifting the value left b50455fab459b0b John Hsu 2016-06-07 370 * so that msb is bit 31 b50455fab459b0b John Hsu 2016-06-07 371 * 0x00231f56 -> 0x8C7D5800 b50455fab459b0b John Hsu 2016-06-07 372 * the result is y * 2^31 -> "significand" b50455fab459b0b John Hsu 2016-06-07 373 * then the highest 9 bits are used for a table lookup b50455fab459b0b John Hsu 2016-06-07 374 * the highest bit is discarded because it's always set b50455fab459b0b John Hsu 2016-06-07 375 * the highest nine bits in our example are 100011000 b50455fab459b0b John Hsu 2016-06-07 376 * so we would use the entry 0x18 b50455fab459b0b John Hsu 2016-06-07 377 */ b50455fab459b0b John Hsu 2016-06-07 378 significand = value << (31 - msb); b50455fab459b0b John Hsu 2016-06-07 379 logentry = (significand >> 23) & 0xff; b50455fab459b0b John Hsu 2016-06-07 380 /** b50455fab459b0b John Hsu 2016-06-07 381 * last step we do is interpolation because of the b50455fab459b0b John Hsu 2016-06-07 382 * limitations of the log table the error is that part of b50455fab459b0b John Hsu 2016-06-07 383 * the significand which isn't used for lookup then we b50455fab459b0b John Hsu 2016-06-07 384 * compute the ratio between the error and the next table entry b50455fab459b0b John Hsu 2016-06-07 385 * and interpolate it between the log table entry used and the b50455fab459b0b John Hsu 2016-06-07 386 * next one the biggest error possible is 0x7fffff b50455fab459b0b John Hsu 2016-06-07 387 * (in our example it's 0x7D5800) b50455fab459b0b John Hsu 2016-06-07 388 * needed value for next table entry is 0x800000 b50455fab459b0b John Hsu 2016-06-07 389 * so the interpolation is b50455fab459b0b John Hsu 2016-06-07 390 * (error / 0x800000) * (logtable_next - logtable_current) b50455fab459b0b John Hsu 2016-06-07 391 * in the implementation the division is moved to the end for b50455fab459b0b John Hsu 2016-06-07 392 * better accuracy there is also an overflow correction if b50455fab459b0b John Hsu 2016-06-07 393 * logtable_next is 256 b50455fab459b0b John Hsu 2016-06-07 394 */ b50455fab459b0b John Hsu 2016-06-07 395 interpolation = ((significand & 0x7fffff) * b50455fab459b0b John Hsu 2016-06-07 396 ((logtable[(logentry + 1) & 0xff] - b50455fab459b0b John Hsu 2016-06-07 397 logtable[logentry]) & 0xffff)) >> 15; b50455fab459b0b John Hsu 2016-06-07 398 b50455fab459b0b John Hsu 2016-06-07 399 log2val = ((msb << 24) + (logtable[logentry] << 8) + interpolation); b50455fab459b0b John Hsu 2016-06-07 400 /** b50455fab459b0b John Hsu 2016-06-07 401 * log10(x) = log2(x) * log10(2) b50455fab459b0b John Hsu 2016-06-07 402 */ b50455fab459b0b John Hsu 2016-06-07 403 log10val = (log2val * LOG10_MAGIC) >> 31; b50455fab459b0b John Hsu 2016-06-07 404 /** b50455fab459b0b John Hsu 2016-06-07 405 * the result is round off to 3 decimal b50455fab459b0b John Hsu 2016-06-07 406 */ b50455fab459b0b John Hsu 2016-06-07 407 return log10val / ((1 << 24) / 1000); b50455fab459b0b John Hsu 2016-06-07 408 } b50455fab459b0b John Hsu 2016-06-07 409 :::::: The code at line 358 was first introduced by commit :::::: b50455fab459b0ba17f6129203f77c6acce946ce ASoC: nau8825: cross talk suppression measurement function :::::: TO: John Hsu <KCHSU0(a)nuvoton.com&gt; :::::: CC: Mark Brown <broonie(a)kernel.org&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org