mirror of https://github.com/torvalds/linux.git
18429c51c7
When invoking function cfg80211_calculate_bitrate_eht about (320 MHz, EHT-MCS 13, EHT-NSS 2, EHT-GI 0), which means the parameters as flags: 0x80, bw: 7, mcs: 13, eht_gi: 0, nss: 2, this formula (result * rate->nss) will overflow and causes the returned bitrate to be 3959 when it should be 57646. Here is the explanation: u64 tmp; u32 result; … /* tmp = result = 4 * rates_996[0] * = 4 * 480388888 = 0x72889c60 */ tmp = result; /* tmp = 0x72889c60 * 6144 = 0xabccea90000 */ tmp *= SCALE; /* tmp = 0xabccea90000 / mcs_divisors[13] * = 0xabccea90000 / 5120 = 0x8970bba6 */ do_div(tmp, mcs_divisors[rate->mcs]); /* result = 0x8970bba6 */ result = tmp; /* normally (result * rate->nss) = 0x8970bba6 * 2 = 0x112e1774c, * but since result is u32, (result * rate->nss) = 0x12e1774c, * overflow happens and it loses the highest bit. * Then result = 0x12e1774c / 8 = 39595753, */ result = (result * rate->nss) / 8; Signed-off-by: Paul Zhang <quic_paulz@quicinc.com> Signed-off-by: Johannes Berg <johannes.berg@intel.com> |
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| .. | ||
| certs | ||
| .gitignore | ||
| Kconfig | ||
| Makefile | ||
| ap.c | ||
| chan.c | ||
| core.c | ||
| core.h | ||
| debugfs.c | ||
| debugfs.h | ||
| ethtool.c | ||
| ibss.c | ||
| lib80211.c | ||
| lib80211_crypt_ccmp.c | ||
| lib80211_crypt_tkip.c | ||
| lib80211_crypt_wep.c | ||
| mesh.c | ||
| mlme.c | ||
| nl80211.c | ||
| nl80211.h | ||
| ocb.c | ||
| of.c | ||
| pmsr.c | ||
| radiotap.c | ||
| rdev-ops.h | ||
| reg.c | ||
| reg.h | ||
| scan.c | ||
| sme.c | ||
| sysfs.c | ||
| sysfs.h | ||
| trace.c | ||
| trace.h | ||
| util.c | ||
| wext-compat.c | ||
| wext-compat.h | ||
| wext-core.c | ||
| wext-priv.c | ||
| wext-proc.c | ||
| wext-sme.c | ||
| wext-spy.c | ||