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

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Date:	Thu, 29 Dec 2011 01:22:01 +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 29-12-11 00:07, Marcel Holtmann wrote:

>> 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?
>
> the Linux code indeed is broken for not checking the returned page, but
> it is broken for different reasons.
>
> However the expected result from the dongle would be an error code and
> not just returning page 0 instead.

Okay. Just as an additional data point:

I came across the HCI_Read_Local_Supported_Commands command in the spec 
a few pages up and quickly verified that the adapter doesn't in fact 
deny support for the HCI_Read_Local_Extended_Features command.

That is, after applying the below, I do get:

hci_cc_read_local_commands:hci0 status 0x0
hci_cc_read_local_commands:hci0 commands[14] 0xe8

which does claim support for the command (bit 6 of commands[14]).

Thought I'd check since if it hadn't, that would imply a certain fix but 
that can't be used then.

I'll stand by to test whatever final solution is arrived at.

(although I don't personally care, linux 3.0.y and 3.1.y may want it as 
well at that point I guess).

Rene.

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 8fe270c..0ac87ea 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -622,6 +622,7 @@ static void hci_cc_read_local_commands(struct 
hci_dev *hdev, struct sk_buff *skb
                 goto done;

         memcpy(hdev->commands, rp->commands, sizeof(hdev->commands));
+       BT_DBG("%s commands[14] 0x%x", hdev->name, rp->commands[14]);

         if (test_bit(HCI_INIT, &hdev->flags) && (hdev->commands[5] & 0x10))
                 hci_setup_link_policy(hdev);
--
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