Re: [Bluez-devel] question about hci_usb endpoint selection...

[Marcel Holtmann <marcel@holtmann.org>]

Hi Lars,

> I already asked this before, but I want to "nail down" this problem now,
> so I'm asking again and hope that someone can give some suggestions that
> even my stupid brain can understand. If this is the wrong list to ask,
> just point me to the correct one, and I'll post again there.
> 
> The problem is this:
> when using sco and using different voice modes (0x0060 for 16bit/8kHz,
> 0x0040 for 8bit/8kHz), different "alternate settings" have to be used on
> hci_usb.
> 
> The former answer was:
> "Don't use this patch [changing the "alternate settings" selection
> hardcodedly] and accept the default voice setting of 0x0060."
> 
> We really don't want to. There are MANY people out there who want to use
> 16 bit audio, and MANY who want to use 8bit MU_LAW. What has to be done
> to make it possible to change this "alternate setting" when we actually
> *need* not alternate setting "2" (16bit), but use alternate setting "1"
> when needed?
> 
> Marcel pointed out that:
> "You can make use of the notify() callback and adjust the alternate
> setting as needed. Maybe you have to unlink and re-submit the ISOC
> URB's, but the best way is to start the ISOC URB's only when a SCO
> connection is created."
> 
> Uhm, sorry. What? Yes, I'm not firm in kernel hacking, yes, I did not
> RTFM, please just push me into the right direction here. Either API
> documentation href and/or "use this and that function", or just dump
> some lines of pseudo code with "what function comes from what API" so
> that I can get a basic understanding what's going on in hci_usb. What
> notify callback? How to register? Where can I find an example of someone
> else doing this? Where can I find out what an ISOC URB really is?

look at the hci_usb driver and add the notify() callback function for
it. This function gets called when you change the voice setting or a new
connection is added or removed. I changed the connection hash to count
the ACL and SCO links separatly and disabled the tasklet when calling
this function so that the core stops processing TX packets and enable it
after the driver finished anything it has to do.

Regards

Marcel




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