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Date: Wed, 17 Nov 2010 11:13:26 +0530
Message-ID: <AANLkTi=NH8gbW8iCKOQN0bmbL=nqewsZkUik+VkvWUgi@mail.gmail.com>
Subject: Re: [PATCH v5] Bluetooth: btwilink driver
From: Pavan Savoy <pavan_savoy@sify.com>
To: Vitaly Wool <vitalywool@gmail.com>
Cc: "Gustavo F. Padovan" <padovan@profusion.mobi>, marcel@holtmann.org,
	linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org
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On Wed, Nov 17, 2010 at 4:50 AM, Vitaly Wool <vitalywool@gmail.com> wrote:
>>> + =C2=A0 =C2=A0 /* Registration with ST layer is successful,
>>> + =C2=A0 =C2=A0 =C2=A0* hardware is ready to accept commands from HCI c=
ore.
>>> + =C2=A0 =C2=A0 =C2=A0*/
>>> + =C2=A0 =C2=A0 if (test_and_set_bit(HCI_RUNNING, &hdev->flags)) {
>>> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 clear_bit(HCI_RUNNING, &hde=
v->flags);
>>> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 err =3D st_unregister(ST_BT=
);
>>> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 if (err)
>>> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0=
 BT_ERR("st_unregister() failed with error %d", err);
>>> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 hst->st_write =3D NULL;
>>> + =C2=A0 =C2=A0 }
>>
>>
>> What are you trying to do here? test_and_set_bit() result doesn't say
>> nothing about error and you shall put test_and_set_bit should be in the
>> beginning, to know if your device is already opened or not and then
>> clear_bit if some error ocurrs during the function.
>>
>
> Yeap, this piece of code beats me is well. Why is it an error if this
> bit wasn't already set?

Vitaly, Gustavo,

I suppose I never understood HCI_RUNNING flag that way, as in an error
check mechanism to avoid multiple hci0 ups.

What I understood was that HCI_RUNNING suggested as to when hci0 was
ready to be used. With this understanding, I wanted to make sure I
downloaded the firmware for the chip before I proclaim to the world
that the hci0 is ready to be used, as in HCI_RUNNING.

For example, I didn't want my _send_frame to be called before I did
the firmware download - since firmware download takes time - 45kb
send/wait commands :(

But I suppose I now understand - What I would rather do is test_bit in
the beginning of function and do a set_bit at the end of function -
does this make sense ?

> ~Vitaly
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