Return-Path: MIME-Version: 1.0 In-Reply-To: References: <35c90d960912081950t135e3f10m8848e54fde1e596f@mail.gmail.com> <1260335175.2901.20.camel@violet> <35c90d960912082213s26fb0ebse75ce85d43213d9@mail.gmail.com> <1260482634.2901.70.camel@violet> <35c90d960912161359u2b3f9b2fi875288896a7a8478@mail.gmail.com> <35c90d961003091207u66571bt789461dcc7972693@mail.gmail.com> <1268167524.3712.61.camel@localhost.localdomain> Date: Thu, 9 Dec 2010 12:37:56 +0200 Message-ID: Subject: Re: RFC: Allow Bluez to select flushable or non-flushable ACL packets with L2CAP_LM_RELIABLE From: Andrei Emeltchenko To: Nick Pelly Cc: Luiz Augusto von Dentz , Marcel Holtmann , linux-bluetooth@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 List-ID: Hi All, On Wed, Jun 16, 2010 at 5:15 PM, Nick Pelly wrote: > On Wed, Jun 16, 2010 at 4:40 AM, Luiz Augusto von Dentz > wrote: >> Hi, >> >> On Tue, Mar 9, 2010 at 11:45 PM, Marcel Holtmann w= rote: >>> Hi Nick, >>> >>>> >>> >> Right now Bluez always requests flushable ACL packets (but does= not >>>> >>> >> set a flush timeout, so effectively they are non-flushable): >>>> >>> >> >>>> >>> >> However it is desirable to use an ACL flush timeout on A2DP pac= kets so >>>> >>> >> that if the ACL packets block for some reason then the LM can f= lush >>>> >>> >> them to make room for newer packets. >>>> >>> >> >>>> >>> >> Is it reasonable for Bluez to use the 0x00 ACL packet boundary = flag by >>>> >>> >> default (non-flushable packet), and let userspace request flush= able >>>> >>> >> packets on A2DP L2CAP sockets with the socket option >>>> >>> >> L2CAP_LM_RELIABLE. >>>> >>> > >>>> >>> > the reliable option has a different meaning. It comes back from = the old >>>> >>> > Bluetooth 1.1 qualification days where we had to tests on L2CAP = that had >>>> >>> > to confirm that we can detect malformed packets and report them.= These >>>> >>> > days it is just fine to drop them. >>>> >>> >>>> >>> Got it, how about introducing >>>> >>> >>>> >>> #define L2CAP_LM_FLUSHABLE 0x0040 >>>> >> >>>> >> that l2cap_sock_setsockopt_old() sets this didn't give you a hint t= hat >>>> >> we might wanna deprecate this socket options ;) >>>> >> >>>> >> I need to read up on the flushable stuff, but in the end it deserve= s its >>>> >> own socket option. Also an ioctl() to actually trigger Enhanced flu= sh >>>> >> might be needed. >>>> >> >>>> >>> struct l2cap_pinfo { >>>> >>> =A0 =A0... >>>> >>> =A0 =A0__u8 flushable; >>>> >>> } >>>> >> >>>> >> Sure. In the long run we need to turn this into a bitmask. We are j= ust >>>> >> wasting memory here. >>>> > >>>> > Attached is an updated patch, that checks the LMP features bitmask >>>> > before using the new non-flushable packet type. >>>> > >>>> > I am still using L2CAP_LM_FLUSHABLE socket option in >>>> > l2cap_sock_setsockopt_old(), which I don't think you are happy with. >>>> > So how about a new option: >>>> > >>>> > SOL_L2CAP, L2CAP_ACL_FLUSH >>>> > which has a default value of 0, and can be set to 1 to make the ACL >>>> > data sent by this L2CAP socket flushable. >>>> > >>>> > In a later commit we would then add >>>> > SOL_ACL, ACL_FLUSH_TIMEOUT >>>> > That is used to set an automatic flush timeout for the ACL link on a >>>> > L2CAP socket. Note that SOL_ACL is new. >>>> > >>>> > But maybe this is not what you had in mind, so I'm looking for your >>>> > advice before I implement this. >>>> >>>> Attached an updated patch for 2.6.32 kernel. We've been using this >>>> patch successfully on production devices. >>> >>> can see anything wrong with that patch. However we need to use >>> SOL_BLUETOOTH for it of course. So we need to come up with something to >>> make this simple. Nick are you going to take Marcel comments? Otherwise I could take care about the patch as it seems that it might help in some situations. >>> An additional change I like to see is to use flags for booleans like >>> flushable in the structures. Can you work on changing that. >>> >>> Also do we have decoding support for this in hcidump. It might be nice >>> to include some really simple examples in the commit message. At least wireshark which I use understands those packets. >> I would like to play a little bit with this, so is there any missing upd= ates? > > Nope, that is our most recent version. Nick, do you know headset which could help to hear the real difference? I was trying to use Sony DR-BT22 headset which has some issues with A2DP but the solution did not help much. Regards, Andrei