Date: Wed, 12 Apr 2006 10:34:40 -0700 From: Maksim Yevmenkin <maksim.yevmenkin@savvis.net> To: Iain Hibbert <plunky@rya-online.net> Cc: freebsd-bluetooth@freebsd.org Subject: Re: headset/sco support in freebsd Message-ID: <443D3A30.2020109@savvis.net> In-Reply-To: <1144841743.207833.9946.nullmailer@galant.ukfsn.org> References: <20060314181140.GB6870@lbl.pl> <44170EDA.5000406@savvis.net> <1144841743.207833.9946.nullmailer@galant.ukfsn.org>
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Iain, >> i have not committed it yet. there is also a bluetooth sco sockets >> layer to simplify programming api. > > Max, I am working on this now for NetBSD - I had it in mind to use > SOCK_STREAM type with 'HCI' protocol for this but I notice that BlueZ > have declared a BTPROTO_SCO and are using SOCK_SEQPACKET instead. > > My feeling is that I am going with SOCK_STREAM since its clearly a > stream of data, do you have an opinion? well, yes and no. "yes" because sco primary goal is to carry audio/video streams. "no" is because of bluetooth specific. SOCK_STREAM "... provides sequenced, reliable, two-way, connection-based byte streams ..." SOCK_DGRAM "... datagrams (connectionless, unreliable messages of a fixed maximum length) ..." SOCK_SEQPACKET "... provides a sequenced, reliable, two-way connection based data transmission path for datagrams of fixed maximum length; a consumer is required to read an entire packet with each read system call ..." please keep in mind that sco is not really a protocol. it is more of a transport. sco has fixed packet length. sco is not reliable. the way i understand it, sco packets cannot be re-ordered but can be dropped. imo, none of the SOCK_xxx types describes sco exactly. to me its either SOCK_DGRAM/SOCK_SEQPACKET (more preferred) or SOCK_STREAM (less preferred). in my code, i opted for SOCK_SEQPACKET (just like linux) to describe properties of sco "protocol/transport". i guess, it is up to the one who implements sco sockets to choose if SOCK_xxx type describes "protocol" properties or what "protocol" can be used for. in other words sco "protocol" has (some) SOCK_SEQPACKET properties vs. sco "protocol" is/can be used to transfer SOCK_STREAM type of data. thanks, max
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