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

From: Rene Herman
Date: Wed Dec 28 2011 - 19:22:06 EST

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).


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))
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