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RE: [bluetooth-dev] l2cap
> 1. If an app sends an L2CAP signal request (#1), and then
> somebody tries
> to send another one (#2) before the response to #1 comes back the the
> timer on the first one gets clobbered. I expect the AXIS folks already
> know this and are fixing it as they add support for multiple apps...
Yes, currently we only support one packet timer per CID, we will add support for more later on.
> 2. In rfcomm_send_data let's say the data being sent needs to be
> segmented and a credit scheme is in use. If segment #1 is sent, but it
> uses the last credit, this function returns 0 to the caller. Shouldn't
> it return the amount actually sent thus far?
> 3. If I read the spec correctly L2CAP needs to perform segmentation.
> Currently it just drops packets too big for the MTU. Any plans to fix
> this soon?
The segmentation is not done from upper layers down to l2cap, it is done from l2cap down to HCI/LMP.
See spec Ch 2.4
"Segmentation and reassembly (SAR) operations are used to improve efficiency
by supporting a maximum transmission unit (MTU) size larger than the largest
All L2CAP packets may be segmented for transfer over Baseband packets. The
protocol does not perform any segmentation and reassembly operations but
the packet format supports adaptation to smaller physical frame sizes. An
L2CAP implementation exposes the outgoing (i.e., the remote host's receiving) MTU and segments higher layer packets into 'chunks' that can be passed to the Link Manager via the Host Controller Interface (HCI), whenever one exists."
"On the receiving side, an L2CAP implementation receives 'chunks' from the
HCI and reassembles those chunks into L2CAP packets using information pro-vided through the HCI and from the packet header."
2.4.1 Segmentation Procedures
"The L2CAP maximum transmission unit (MTU) will be exported using an imple-mentation specific service interface. "
"It is the responsibility of the higher layer protocol to limit the size of packets sent to the L2CAP layer below the MTU limit."
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