docs: networking: convert radiotap-headers.txt to ReST

- add SPDX header;
- adjust title markup;
- mark code blocks and literals as such;
- adjust identation, whitespaces and blank lines where needed;
- add to networking/index.rst.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/index.rst

@@ -95,6 +95,7 @@ Contents:
    plip
    ppp_generic
    proc_net_tcp
+   radiotap-headers
 
 .. only::  subproject and html
 

Documentation/networking/mac80211-injection.rst

@@ -13,7 +13,7 @@ following format::
  [ payload ]
 
 The radiotap format is discussed in
-./Documentation/networking/radiotap-headers.txt.
+./Documentation/networking/radiotap-headers.rst.
 
 Despite many radiotap parameters being currently defined, most only make sense
 to appear on received packets.  The following information is parsed from the

Documentation/networking/radiotap-headers.rst

@@ -1,3 +1,6 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===========================
 How to use radiotap headers
 ===========================
 
@@ -5,9 +8,9 @@ Pointer to the radiotap include file
 ------------------------------------
 
 Radiotap headers are variable-length and extensible, you can get most of the
-information you need to know on them from:
+information you need to know on them from::
 
-./include/net/ieee80211_radiotap.h
+    ./include/net/ieee80211_radiotap.h
 
 This document gives an overview and warns on some corner cases.
 
@@ -21,6 +24,8 @@ of the it_present member of ieee80211_radiotap_header is set, it means that
 the header for argument index 0 (IEEE80211_RADIOTAP_TSFT) is present in the
 argument area.
 
+::
+
    < 8-byte ieee80211_radiotap_header >
    [ <possible argument bitmap extensions ... > ]
    [ <argument> ... ]
@@ -76,6 +81,8 @@ ieee80211_radiotap_header.
 Example valid radiotap header
 -----------------------------
 
+::
+
 	0x00, 0x00, // <-- radiotap version + pad byte
 	0x0b, 0x00, // <- radiotap header length
 	0x04, 0x0c, 0x00, 0x00, // <-- bitmap
@@ -89,64 +96,64 @@ Using the Radiotap Parser
 
 If you are having to parse a radiotap struct, you can radically simplify the
 job by using the radiotap parser that lives in net/wireless/radiotap.c and has
-its prototypes available in include/net/cfg80211.h.  You use it like this:
+its prototypes available in include/net/cfg80211.h.  You use it like this::
 
-#include <net/cfg80211.h>
+    #include <net/cfg80211.h>
 
-/* buf points to the start of the radiotap header part */
+    /* buf points to the start of the radiotap header part */
 
-int MyFunction(u8 * buf, int buflen)
-{
-	int pkt_rate_100kHz = 0, antenna = 0, pwr = 0;
-	struct ieee80211_radiotap_iterator iterator;
-	int ret = ieee80211_radiotap_iterator_init(&iterator, buf, buflen);
+    int MyFunction(u8 * buf, int buflen)
+    {
+	    int pkt_rate_100kHz = 0, antenna = 0, pwr = 0;
+	    struct ieee80211_radiotap_iterator iterator;
+	    int ret = ieee80211_radiotap_iterator_init(&iterator, buf, buflen);
 
-	while (!ret) {
+	    while (!ret) {
 
-		ret = ieee80211_radiotap_iterator_next(&iterator);
+		    ret = ieee80211_radiotap_iterator_next(&iterator);
 
-		if (ret)
-			continue;
+		    if (ret)
+			    continue;
 
-		/* see if this argument is something we can use */
+		    /* see if this argument is something we can use */
 
-		switch (iterator.this_arg_index) {
-		/*
-		 * You must take care when dereferencing iterator.this_arg
-		 * for multibyte types... the pointer is not aligned.  Use
-		 * get_unaligned((type *)iterator.this_arg) to dereference
-		 * iterator.this_arg for type "type" safely on all arches.
-		 */
-		case IEEE80211_RADIOTAP_RATE:
-			/* radiotap "rate" u8 is in
-			 * 500kbps units, eg, 0x02=1Mbps
-			 */
-			pkt_rate_100kHz = (*iterator.this_arg) * 5;
-			break;
+		    switch (iterator.this_arg_index) {
+		    /*
+		    * You must take care when dereferencing iterator.this_arg
+		    * for multibyte types... the pointer is not aligned.  Use
+		    * get_unaligned((type *)iterator.this_arg) to dereference
+		    * iterator.this_arg for type "type" safely on all arches.
+		    */
+		    case IEEE80211_RADIOTAP_RATE:
+			    /* radiotap "rate" u8 is in
+			    * 500kbps units, eg, 0x02=1Mbps
+			    */
+			    pkt_rate_100kHz = (*iterator.this_arg) * 5;
+			    break;
 
-		case IEEE80211_RADIOTAP_ANTENNA:
-			/* radiotap uses 0 for 1st ant */
-			antenna = *iterator.this_arg);
-			break;
+		    case IEEE80211_RADIOTAP_ANTENNA:
+			    /* radiotap uses 0 for 1st ant */
+			    antenna = *iterator.this_arg);
+			    break;
 
-		case IEEE80211_RADIOTAP_DBM_TX_POWER:
-			pwr = *iterator.this_arg;
-			break;
+		    case IEEE80211_RADIOTAP_DBM_TX_POWER:
+			    pwr = *iterator.this_arg;
+			    break;
 
-		default:
-			break;
-		}
-	}  /* while more rt headers */
+		    default:
+			    break;
+		    }
+	    }  /* while more rt headers */
 
-	if (ret != -ENOENT)
-		return TXRX_DROP;
+	    if (ret != -ENOENT)
+		    return TXRX_DROP;
 
-	/* discard the radiotap header part */
-	buf += iterator.max_length;
-	buflen -= iterator.max_length;
+	    /* discard the radiotap header part */
+	    buf += iterator.max_length;
+	    buflen -= iterator.max_length;
 
-	...
+	    ...
 
-}
+    }
 
 Andy Green <andy@warmcat.com>

include/net/cfg80211.h

@@ -5211,7 +5211,7 @@ u32 ieee80211_mandatory_rates(struct ieee80211_supported_band *sband,
  * Radiotap parsing functions -- for controlled injection support
  *
  * Implemented in net/wireless/radiotap.c
- * Documentation in Documentation/networking/radiotap-headers.txt
+ * Documentation in Documentation/networking/radiotap-headers.rst
  */
 
 struct radiotap_align_size {

net/wireless/radiotap.c

@@ -90,7 +90,7 @@ static const struct ieee80211_radiotap_namespace radiotap_ns = {
  * iterator.this_arg for type "type" safely on all arches.
  *
  * Example code:
- * See Documentation/networking/radiotap-headers.txt
+ * See Documentation/networking/radiotap-headers.rst
  */
 
 int ieee80211_radiotap_iterator_init(