On Wed, Dec 16, 2009 at 1:59 PM, Nick Pelly <npelly@xxxxxxxxxx> wrote:
> Hi Marcel,
>
> On Thu, Dec 10, 2009 at 2:03 PM, Marcel Holtmann <marcel@xxxxxxxxxxxx> wrote:
>> 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 packets so
>>> >> that if the ACL packets block for some reason then the LM can flush
>>> >> 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 flushable
>>> >> 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 that
>> we might wanna deprecate this socket options ;)
>>
>> I need to read up on the flushable stuff, but in the end it deserves its
>> own socket option. Also an ioctl() to actually trigger Enhanced flush
>> might be needed.
>>
>>> struct l2cap_pinfo {
>>> ...
>>> __u8 flushable;
>>> }
>>
>> Sure. In the long run we need to turn this into a bitmask. We are just
>> 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.
Nick
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0001-Bluetooth-Use-non-flushable-pb-flag-by-default-for-A.patch
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