General BT q. on profiles and support for (PC USB adaptors)

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Breezer - 20 Nov 2004 15:26 GMT

This might not be the perfect choice of group for asking this Q but I can't
find anywhere else more appropriate without going through a sign-up as a BT
developer or something, but I'm hoping someone will know:

With USB Bluetooth adaptors for the PC, does the dongle need to know about
profiles and have support for them, or does that part of the hardware purely
handle the data link layer? Are profiles all handled by software drivers or
higher level parts of the applications that use them?

I'm wondering, because although I use Windows (98SE) a fair bit, I plan on
using a BT adapter in Linux and if the manufacturers drivers aren't
important, that means I can purely base my purchase decision on (as long as
it's a supported chipset in the device, but most are nowadays) the class
(distance range), brand and cost. It'll mainly be for headset type stuff but
with some synching and file transfer.

Is it also the same with encryption/security protocols
(hard/firmware/drivers?). Some adaptors have flashable firmware I believe.

If the hardware needs support for every profile it can use then it makes it
a harder decision. Does it?

Thanks in advance anyone who knows, would appreciate an answer.

John

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Henryk =?ISO-8859-15?Q?Pl=F6tz?= - 21 Nov 2004 06:52 GMT

Moin,

Am Sat, 20 Nov 2004 15:28:55 -0000 schrieb Breezer:

> With USB Bluetooth adaptors for the PC, does the dongle need to know
> about profiles and have support for them, or does that part of the
> hardware purely handle the data link layer? Are profiles all handled
> by software drivers or higher level parts of the applications that use
> them?

The latter is true. A Bluetooth dongle seldomly is more than a fancy
kind of network device and most useful things are done in software. The
dongle vendors however have mostly resorted to lying to you, saying
"This dongle will only support profiles A, B and C, but not D and E"
when they really should say "The windows software we ship with this
dongle will only support ...; oh, and Bluetooth with windows is a mess,
so you can't use any other software apart from ours easily." (This is
similar to selling a network card that "only can do SMTP and FTP, but
not HTTP".)

When you intend to use Linux you'll most likely won't have to worry
about that windows mess and only look at what Bluetooth with Linux
(which basically means "BlueZ") can do. See http://www.bluez.org and
http://www.holtmann.org/linux/bluetooth/ for more information.

That being said there certainly is the possibility to cripple a dongle
in such a way that it can't be used for some profiles. For example
Bluetooth has different packet types and usually not all are needed, so
the vendor might decide to save some microcents by not implementing all
of them. Some profiles however will depend on certain types. And then
of course there will probably always be bugs in some firmware
implementations.

You should find almost all information available about that topic on the
both sites mentioned above. And of course you can ask your remaining
questions on the bluez mailing lists (look through the archives before
doing that).

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Henryk Plötz
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