Re: [RFC 1/3] cfg80211: Add support for HE

[Arend van Spriel]

On 5/25/2018 12:11 PM, Luca Coelho wrote:
+static int
> >+nl80211_send_ift_data(struct sk_buff *msg,
> >+                    const struct ieee80211_sband_iftype_data *iftdata)
>
>make it nl80211_send_iftype_data.
Okay, I'll replace all ift instances to iftype.

My comment is mainly about function names.

> >   static int nl80211_send_band_rateinfo(struct sk_buff *msg,
> >                                     struct ieee80211_supported_band *sband)
> >   {
> >@@ -1353,6 +1383,32 @@ static int nl80211_send_band_rateinfo(struct sk_buff 
*msg,
> >                        sband->vht_cap.cap)))
> >               return -ENOBUFS;
> >
> >+      if (sband->n_iftype_data) {
> >+              struct nlattr *nl_iftype_data =
> >+                      nla_nest_start(msg, NL80211_BAND_ATTR_IFTYPE_DATA);
> >+              int err;
> >+
> >+              if (!nl_iftype_data)
> >+                      return -ENOBUFS;
> >+
> >+              for (i = 0; i < sband->n_iftype_data; i++) {
> >+                      struct nlattr *iftdata;
> >+
> >+                      iftdata = nla_nest_start(msg, i + 1);
> >+                      if (!iftdata)
> >+                              return -ENOBUFS;
>
>bit inconsistent dealing with error path. Here errno is returned....
>
> >@@ -4490,6 +4549,19 @@ static bool nl80211_put_sta_rate(struct sk_buff *msg, 
struct rate_info *info,
> >               if (info->flags & RATE_INFO_FLA
                        return false;
> >+      } else if (info->flags & RATE_INFO_FLAGS_HE_MCS) {
> >+              if (nla_put_u8(msg, NL80211_RATE_INFO_HE_MCS, info->mcs))
> >+                      return false;
>
>... and here bool is returned. Admittedly, this seems to have been the
>case already before this patch.

Sure.


> >diff --git a/net/wireless/util.c b/net/wireless/util.c
> >index d112e9a89364..b66a68a41cd6 100644
> >--- a/net/wireless/util.c
> >+++ b/net/wireless/util.c
> >@@ -4,6 +4,7 @@
> >    *
> >    * Copyright 2007-2009      Johannes Berg<johan...@sipsolutions.net>
> >    * Copyright 2013-2014  Intel Mobile Communications GmbH
> >+ * Copyright 2017     Intel Deutschland GmbH
> >    */
> >   #include <linux/export.h>
> >   #include <linux/bitops.h>
> >@@ -1142,6 +1143,85 @@ static u32 cfg80211_calculate_bitrate_vht(struct 
rate_info *rate)
> >       return 0;
> >   }
> >
> >+static u32 cfg80211_calculate_bitrate_he(struct rate_info *rate)
> >+{
> >+#define SCALE 2048
> >+      u16 mcs_divisors[12] = {
> >+              34133, /* 16.666666... */
> >+              17067, /*  8.333333... */
> >+              11378, /*  5.555555... */
> >+               8533, /*  4.166666... */
> >+               5689, /*  2.777777... */
> >+               4267, /*  2.083333... */
> >+               3923, /*  1.851851... */
> >+               3413, /*  1.666666... */
> >+               2844, /*  1.388888... */
> >+               2560, /*  1.250000... */
> >+               2276, /*  1.111111... */
> >+               2048, /*  1.000000... */
> >+      };
> >+      u32 rates_160M[3] = { 960777777, 907400000, 816666666 };
> >+      u32 rates_969[3] =  { 480388888, 453700000, 408333333 };
> >+      u32 rates_484[3] =  { 229411111, 216666666, 195000000 };
> >+      u32 rates_242[3] =  { 114711111, 108333333,  97500000 };
> >+      u32 rates_106[3] =  {  40000000,  37777777,  34000000 };
> >+      u32 rates_52[3]  =  {  18820000,  17777777,  16000000 };
> >+      u32 rates_26[3]  =  {   9411111,   8888888,   8000000 };
> >+      u64 tmp;
> >+      u32 result;
> >+
> >+      if (WARN_ON_ONCE(rate->mcs > 11))
> >+              return 0;
> >+
> >+      if (WARN_ON_ONCE(rate->he_gi > NL80211_RATE_INFO_HE_GI_3_2))
> >+              return 0;
> >+      if (WARN_ON_ONCE(rate->he_ru_alloc >
> >+                       NL80211_RATE_INFO_HE_RU_ALLOC_2x996))
> >+              return 0;
> >+      if (WARN_ON_ONCE(rate->nss < 1 || rate->nss > 8))
> >+              return 0;
> >+
> >+      if (rate->bw == RATE_INFO_BW_160)
> >+              result = rates_160M[rate->he_gi];
> >+      else if (rate->bw == RATE_INFO_BW_80 ||
> >+               (rate->bw == RATE_INFO_BW_HE_RU &&
> >+                rate->he_ru_alloc == NL80211_RATE_INFO_HE_RU_ALLOC_996))
> >+              result = rates_969[rate->he_gi];
> >+      else if (rate->bw == RATE_INFO_BW_40 ||
> >+               (rate->bw == RATE_INFO_BW_HE_RU &&
> >+                rate->he_ru_alloc == NL80211_RATE_INFO_HE_RU_ALLOC_484))
> >+              result = rates_484[rate->he_gi];
> >+      else if (rate->bw == RATE_INFO_BW_20 ||
> >+               (rate->bw == RATE_INFO_BW_HE_RU &&
> >+                rate->he_ru_alloc == NL80211_RATE_INFO_HE_RU_ALLOC_242))
> >+              result = rates_242[rate->he_gi];
> >+      else if (rate->bw == RATE_INFO_BW_HE_RU &&
> >+               rate->he_ru_alloc == NL80211_RATE_INFO_HE_RU_ALLOC_106)
> >+              result = rates_106[rate->he_gi];
> >+      else if (rate->bw == RATE_INFO_BW_HE_RU &&
> >+               rate->he_ru_alloc == NL80211_RATE_INFO_HE_RU_ALLOC_52)
> >+              result = rates_52[rate->he_gi];
> >+      else if (rate->bw == RATE_INFO_BW_HE_RU &&
> >+               rate->he_ru_alloc == NL80211_RATE_INFO_HE_RU_ALLOC_26)
> >+              result = rates_26[rate->he_gi];
> >+      else if (WARN(1, "invalid HE MCS: bw:%d, ru:%d\n",
> >+                    rate->bw, rate->he_ru_alloc))
> >+              return 0;
> >+
>
>Could consider shifts below iso multiply/division.
> >+     /* now scale to the appropriate MCS */
> >+     tmp = result;
> >+     tmp *= SCALE;
>         tmp <<= 11;
> >+     do_div(tmp, mcs_divisors[rate->mcs]);
> >+     result = tmp;
> >+
> >+     /* and take NSS, DCM into account */
> >+     result = (result * rate->nss) / 8;
>         result = (result * rate->nss) >> 3;
> >+     if (rate->he_dcm)
> >+             result /= 2;
>                 result >>= 1;
> >+
> >+     return result;
> >+}
> >+
I'm not sure I agree.  These are divisions and not really shifts, so
IMHO it's clearer as is.  This is not a hot path and the compiler will
probably optimize it in to shifts if possible anyway.  So I won't
change it in my next version.  Feel free to yell if you disagree (and
have a good argument :P).

Not really. It is just that everything was power of 2, but indeed it is 
not used in data path.

Thanks a lot for your review!

No problemo.

Gr. AvS