linux-kernel - Re: [bluetooth] linux-3.x regression (bisected)

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Message-ID: <4EFB957A.5070606@gmail.com>
Date:	Wed, 28 Dec 2011 23:17:30 +0100
From:	Rene Herman <rene.herman@...il.com>
To:	Marcel Holtmann <marcel@...tmann.org>
CC:	Gustavo Padovan <padovan@...fusion.mobi>,
	Andre Guedes <andre.guedes@...nbossa.org>,
	linux-kernel@...r.kernel.org, linux-bluetooth@...r.kernel.org
Subject: Re: [bluetooth] linux-3.x regression (bisected)

On 28-12-11 17:48, Marcel Holtmann wrote:

> < HCI Command: Read Local Extended Features (0x04|0x0004) plen 1
>       page 1
> > HCI Event: Command Complete (0x0e) plen 14
>       Read Local Extended Features (0x04|0x0004) ncmd 1
>       status 0x00 page 0 max 0
>       Features: 0xff 0xfe 0xff 0x7e 0x98 0x19 0x00 0x80
>
> And this is correct. Page 0 is the same as local features. Storing this
> as page 1 is the issue here. We request page 1, but we are getting page
> 0 instead. So yes, the controller is broken, but not as broken as it
> gets us false information.

By the way, while the bluetooth (2.0) spec seems to consist of a 1230 
page document that I am most certainly not going to study ...

... I couldn't help noticing that the HCI_Read_Local_Extended_Features 
command is in fact specified to return "The highest features page number 
which contains non-zero bits for the local device", and if I look at the 
above, it seems to indeed return max=0.

Is it as such not in fact the case that the dongle is spec-compliant, 
whereas it's the linux code that neglects to check that return value in 
order to make sure that it requested a valid page?

Rene.
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