CURLMOPT_PIPELINING.3: extended and clarified

Especially in regards to the multiplexing part.

docs/libcurl/opts/CURLMOPT_PIPELINING.3

@@ -5,7 +5,7 @@
 .\" *                            | (__| |_| |  _ <| |___
 .\" *                             \___|\___/|_| \_\_____|
 .\" *
-.\" * Copyright (C) 1998 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al.
+.\" * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.
 .\" *
 .\" * This software is licensed as described in the file COPYING, which
 .\" * you should have received as part of this distribution. The terms
@@ -22,24 +22,36 @@
 .\"
 .TH CURLMOPT_PIPELINING 3 "17 Jun 2014" "libcurl 7.37.0" "curl_multi_setopt options"
 .SH NAME
-CURLMOPT_PIPELINING \- enable/disable HTTP pipelining
+CURLMOPT_PIPELINING \- enable HTTP pipelining and multiplexing
 .SH SYNOPSIS
 #include <curl/curl.h>
 
-CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_PIPELINING, long bits);
+CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_PIPELINING, long bitmask);
 .SH DESCRIPTION
-Set the \fBbits\fP parameter to 1 to make libcurl use HTTP pipelining for
-HTTP/1.1 transfers done using this multi handle, as far as possible. This
-means that if you add a second request that can use an already existing
-connection, the second request will be \&"piped" on the same connection rather
-than being executed in parallel.
+Pass in the \fBbitmask\fP parameter to instruct libcurl to enable HTTP
+pipelining and/or HTTP/2 multiplexing for this multi handle.
 
-When using pipelining, there are also several other related options that are
-interesting to tweak and adjust to alter how libcurl spreads out requests on
-different connections or not etc.
+When enabled, libcurl will attempt to use those protocol features when doing
+parallel requests to the same hosts.
 
-Starting in 7.43.0, the \fBbits\fP parameter's bit 1 also has a meaning and
-libcurl is now offering symbol names for the bits:
+For pipelining, this means that if you add a second request that can use an
+already existing connection, the second request will be \&"piped" on the same
+connection rather than being executed in parallel.
+
+For multiplexing, this means that follow-up requests can re-use an existing
+connection and send the new request multiplexed over that at the same time as
+other transfers are already done of that single connection.
+
+There are several other related options that are interesting to tweak and
+adjust to alter how libcurl spreads out requests on different connections or
+not etc.
+
+Before 7.43.0, this option was set to 1 and 0 to enable and disable HTTP/1.1
+pipelining.
+
+Starting in 7.43.0, \fBbitmask\fP's second bit also has a meaning, and you can
+ask for pipelining and multiplexing independently of each other by toggling
+the correct bits.
 .IP CURLPIPE_NOTHING (0)
 Default, which means doing no attempts at pipelining or multiplexing.
 .IP CURLPIPE_HTTP1 (1)
@@ -49,7 +61,7 @@ connections that are already established and in use to hosts.
 If this bit is set, libcurl will try to multiplex the new transfer over an
 existing connection if possible. This requires HTTP/2.
 .SH DEFAULT
-0 (off)
+0 (both pipeline and multiplexing are off)
 .SH PROTOCOLS
 HTTP(S)
 .SH EXAMPLE