Re: [Bluez-devel] hcidump EDR packet type

[Marcel Holtmann <marcel@holtmann.org>]

Hi Mayank,

> > Wondering someone can help to enlighten me on where hci packet type bit
> > is reversed for  change connection packet type command (issued by
> > hcitool) for EDR mode, based on the below hcidump, seems 0x2000 is
> > passed down (which should be 0x1306), however, return message ptype
> > 0x1306 is correct even decoding is not right.
> 
> In case you wanted to change the packet type to 3-DH5 0x2000 is
> perfectly fine since EDR packets are inverted i.e. they will be selected
> if the corresponding bit is 0 and not 1. Internally, before sending the
> change connection packet type command all stacks (hopefully BlueZ as
> well) will xor the packet mask with the EDR packet type list. Thus if
> you enabled an EDR packet (eg 0x2000 for 3-DH5), the bit for 3-DH5 will
> be made 0 and bits for remaining EDR packets shall be made 1.
> 
> 0x1306 means that 3-DH5 and DM1 have been selected on the ACL link which
> is logical since DM1 is by default selected on all ACL links and you
> just changed the packet type to 3-DH5.

actually it is totally wrong. Sending the 3-DH5 bit only means that you
wanna enable DM1 and all EDR packets except 3-DH5, because setting that
bit means you disable that packet type. The corresponding response
should be DM1 + 3-DH5 bit set.

Since this is custom firmware, it is interpreting the bitmask of the
change connection packet type in the wrong way.

And to be clear on this, I don't care about the packet mask at all and
nobody should mess with it (except for testing). Let the link manager
decide which packet type to use. BlueZ can't make any intelligent
decision on which is the best packet type. It doesn't know anything
about the piconet it is using besides its handle.

Regards

Marcel



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