From 8d836581f9b1f57ceaa2b47654754ef1260b410b Mon Sep 17 00:00:00 2001 From: Niklas Cassel Date: Wed, 16 Sep 2026 15:00:32 +0200 Subject: ata: libata-scsi: fix ata_dsm_trim_pages() kernel-doc make htmldocs fails with: Documentation/driver-api/libata:604: ./drivers/ata/libata-scsi.c:2301: ERROR: Unexpected indentation. [docutils] The Return: section of ata_dsm_trim_pages() ends its first sentence with a colon and continues with an indented bullet list. reStructuredText requires a blank line before an indented block, so docutils chokes on the list. Simply adding the missing blank line does not work either: Return: is a kernel-doc "special section", which is terminated by the first blank line, so the bullet list would end up in the Description section, detached from the sentence introducing it. Spell the two bounds out as prose instead, so that the Return: section stays self-contained. Documentation-only change. Fixes: e64e6b5dc867 ("ata: libata-scsi: scale DSM TRIM payload by MAX PAGES PER DSM COMMAND") Reported-by: Thomas Huth Closes: https://lore.kernel.org/linux-ide/b0a0b8e8-cc4f-4c7b-8bc5-fee0712d405a@redhat.com/ Reviewed-by: Damien Le Moal Reviewed-by: Thomas Huth Link: https://lore.kernel.org/r/20260916130031.29990-2-cassel@kernel.org Signed-off-by: Niklas Cassel --- lib/math/int_log.c | 133 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 133 insertions(+) create mode 100644 lib/math/int_log.c (limited to 'lib/math/int_log.c') diff --git a/lib/math/int_log.c b/lib/math/int_log.c new file mode 100644 index 000000000..8f9da3a2a --- /dev/null +++ b/lib/math/int_log.c @@ -0,0 +1,133 @@ +// SPDX-License-Identifier: LGPL-2.1-or-later +/* + * Provides fixed-point logarithm operations. + * + * Copyright (C) 2006 Christoph Pfister (christophpfister@gmail.com) + */ + +#include +#include +#include +#include +#include + +#include + +static const unsigned short logtable[256] = { + 0x0000, 0x0171, 0x02e0, 0x044e, 0x05ba, 0x0725, 0x088e, 0x09f7, + 0x0b5d, 0x0cc3, 0x0e27, 0x0f8a, 0x10eb, 0x124b, 0x13aa, 0x1508, + 0x1664, 0x17bf, 0x1919, 0x1a71, 0x1bc8, 0x1d1e, 0x1e73, 0x1fc6, + 0x2119, 0x226a, 0x23ba, 0x2508, 0x2656, 0x27a2, 0x28ed, 0x2a37, + 0x2b80, 0x2cc8, 0x2e0f, 0x2f54, 0x3098, 0x31dc, 0x331e, 0x345f, + 0x359f, 0x36de, 0x381b, 0x3958, 0x3a94, 0x3bce, 0x3d08, 0x3e41, + 0x3f78, 0x40af, 0x41e4, 0x4319, 0x444c, 0x457f, 0x46b0, 0x47e1, + 0x4910, 0x4a3f, 0x4b6c, 0x4c99, 0x4dc5, 0x4eef, 0x5019, 0x5142, + 0x526a, 0x5391, 0x54b7, 0x55dc, 0x5700, 0x5824, 0x5946, 0x5a68, + 0x5b89, 0x5ca8, 0x5dc7, 0x5ee5, 0x6003, 0x611f, 0x623a, 0x6355, + 0x646f, 0x6588, 0x66a0, 0x67b7, 0x68ce, 0x69e4, 0x6af8, 0x6c0c, + 0x6d20, 0x6e32, 0x6f44, 0x7055, 0x7165, 0x7274, 0x7383, 0x7490, + 0x759d, 0x76aa, 0x77b5, 0x78c0, 0x79ca, 0x7ad3, 0x7bdb, 0x7ce3, + 0x7dea, 0x7ef0, 0x7ff6, 0x80fb, 0x81ff, 0x8302, 0x8405, 0x8507, + 0x8608, 0x8709, 0x8809, 0x8908, 0x8a06, 0x8b04, 0x8c01, 0x8cfe, + 0x8dfa, 0x8ef5, 0x8fef, 0x90e9, 0x91e2, 0x92db, 0x93d2, 0x94ca, + 0x95c0, 0x96b6, 0x97ab, 0x98a0, 0x9994, 0x9a87, 0x9b7a, 0x9c6c, + 0x9d5e, 0x9e4f, 0x9f3f, 0xa02e, 0xa11e, 0xa20c, 0xa2fa, 0xa3e7, + 0xa4d4, 0xa5c0, 0xa6ab, 0xa796, 0xa881, 0xa96a, 0xaa53, 0xab3c, + 0xac24, 0xad0c, 0xadf2, 0xaed9, 0xafbe, 0xb0a4, 0xb188, 0xb26c, + 0xb350, 0xb433, 0xb515, 0xb5f7, 0xb6d9, 0xb7ba, 0xb89a, 0xb97a, + 0xba59, 0xbb38, 0xbc16, 0xbcf4, 0xbdd1, 0xbead, 0xbf8a, 0xc065, + 0xc140, 0xc21b, 0xc2f5, 0xc3cf, 0xc4a8, 0xc580, 0xc658, 0xc730, + 0xc807, 0xc8de, 0xc9b4, 0xca8a, 0xcb5f, 0xcc34, 0xcd08, 0xcddc, + 0xceaf, 0xcf82, 0xd054, 0xd126, 0xd1f7, 0xd2c8, 0xd399, 0xd469, + 0xd538, 0xd607, 0xd6d6, 0xd7a4, 0xd872, 0xd93f, 0xda0c, 0xdad9, + 0xdba5, 0xdc70, 0xdd3b, 0xde06, 0xded0, 0xdf9a, 0xe063, 0xe12c, + 0xe1f5, 0xe2bd, 0xe385, 0xe44c, 0xe513, 0xe5d9, 0xe69f, 0xe765, + 0xe82a, 0xe8ef, 0xe9b3, 0xea77, 0xeb3b, 0xebfe, 0xecc1, 0xed83, + 0xee45, 0xef06, 0xefc8, 0xf088, 0xf149, 0xf209, 0xf2c8, 0xf387, + 0xf446, 0xf505, 0xf5c3, 0xf680, 0xf73e, 0xf7fb, 0xf8b7, 0xf973, + 0xfa2f, 0xfaea, 0xfba5, 0xfc60, 0xfd1a, 0xfdd4, 0xfe8e, 0xff47, +}; + +unsigned int intlog2(u32 value) +{ + /** + * returns: log2(value) * 2^24 + * wrong result if value = 0 (log2(0) is undefined) + */ + unsigned int msb; + unsigned int logentry; + unsigned int significand; + unsigned int interpolation; + + if (unlikely(value == 0)) { + WARN_ON(1); + return 0; + } + + /* first detect the msb (count begins at 0) */ + msb = fls(value) - 1; + + /** + * now we use a logtable after the following method: + * + * log2(2^x * y) * 2^24 = x * 2^24 + log2(y) * 2^24 + * where x = msb and therefore 1 <= y < 2 + * first y is determined by shifting the value left + * so that msb is bit 31 + * 0x00231f56 -> 0x8C7D5800 + * the result is y * 2^31 -> "significand" + * then the highest 9 bits are used for a table lookup + * the highest bit is discarded because it's always set + * the highest nine bits in our example are 100011000 + * so we would use the entry 0x18 + */ + significand = value << (31 - msb); + logentry = (significand >> 23) % ARRAY_SIZE(logtable); + + /** + * last step we do is interpolation because of the + * limitations of the log table the error is that part of + * the significand which isn't used for lookup then we + * compute the ratio between the error and the next table entry + * and interpolate it between the log table entry used and the + * next one the biggest error possible is 0x7fffff + * (in our example it's 0x7D5800) + * needed value for next table entry is 0x800000 + * so the interpolation is + * (error / 0x800000) * (logtable_next - logtable_current) + * in the implementation the division is moved to the end for + * better accuracy there is also an overflow correction if + * logtable_next is 256 + */ + interpolation = ((significand & 0x7fffff) * + ((logtable[(logentry + 1) % ARRAY_SIZE(logtable)] - + logtable[logentry]) & 0xffff)) >> 15; + + /* now we return the result */ + return ((msb << 24) + (logtable[logentry] << 8) + interpolation); +} +EXPORT_SYMBOL(intlog2); + +unsigned int intlog10(u32 value) +{ + /** + * returns: log10(value) * 2^24 + * wrong result if value = 0 (log10(0) is undefined) + */ + u64 log; + + if (unlikely(value == 0)) { + WARN_ON(1); + return 0; + } + + log = intlog2(value); + + /** + * we use the following method: + * log10(x) = log2(x) * log10(2) + */ + + return (log * 646456993) >> 31; +} +EXPORT_SYMBOL(intlog10); -- cgit v1.3.1