Hi Marcel,
On 15.06.2011 13:08, Marcel Holtmann wrote:
Hi Andrzej,
Following patches add possibility to specify custom parameters for
outgoing (e)SCO link. This is implemented as SCO socket options.
This change allows to use reference parameters as defined in HFP 1.5
specification as well as support for future enchancements as wideband
speech as defined in HFP 1.6 draft (uses different air coding format).
Additional socket option (patch 3) allows to disable automatic retry
in case of failure which fallbacks from eSCO to SCO connection in
current implementation. Such fallback should not happen when using
wideband speech which mandates using of eSCO transport.
I am not a big fan of just stupidly exposing all possible HCI value to
userspace and let userspace set them. Especially since in the end there
are no real variation here anyway. There are just a 2-3 use cases for
your SCO socket.
There's L2CAP_OPTIONS sockopt which allows to do pretty much the same
for L2CAP sockets so I just followed it.
What do you mean by just 2-3 use cases for SCO socket? You consider only
HFP as use case for SCO socket? I saw devices which use eSCO to stream
music to mono headsets which do not support A2DP, this may require
custom requirements which we cannot predict. This is only one example,
but user can "invent" something else.
I would rather have simple mode to hand to the kernel and let it do the
right thing (including negotiation and downgrading to SCO) than having
userspace opening sockets over sockets again.
By making such change you actually incorporate part of profiles into
kernel. I don't think this is good idea. My understanding is that
profiles should be in user-space.
And I don't recall any other profile than HFP that uses eSCO, so if
we're going to implement "modes" using this spec, user won't have many
options to choose from. See example above (music over eSCO).
So what are the actual modes for HFP that need to be supported and what
is the range of possible SCO and eSCO options?
At the moment only HFP 1.5 defines reference parameters for eSCO link.
In HFP 1.6 draft there are additional reference parameters for CVSD over
SCO and mSBC over eSCO. And in future profiles you never know what BT
SIG will invent :)
BR,
Andrzej
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