linux-kernel - Re: [PATCH v5] Bluetooth: btwilink driver

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Date:	Wed, 17 Nov 2010 14:52:48 -0200
From:	"Gustavo F. Padovan" <padovan@...fusion.mobi>
To:	Pavan Savoy <pavan_savoy@...y.com>
Cc:	Vitaly Wool <vitalywool@...il.com>, marcel@...tmann.org,
	linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] Bluetooth: btwilink driver

Hi Pavan,

* Pavan Savoy <pavan_savoy@...y.com> [2010-11-17 11:13:26 +0530]:

> On Wed, Nov 17, 2010 at 4:50 AM, Vitaly Wool <vitalywool@...il.com> wrote:
> >>> +     /* Registration with ST layer is successful,
> >>> +      * hardware is ready to accept commands from HCI core.
> >>> +      */
> >>> +     if (test_and_set_bit(HCI_RUNNING, &hdev->flags)) {
> >>> +             clear_bit(HCI_RUNNING, &hdev->flags);
> >>> +             err = st_unregister(ST_BT);
> >>> +             if (err)
> >>> +                     BT_ERR("st_unregister() failed with error %d", err);
> >>> +             hst->st_write = NULL;
> >>> +     }
> >>
> >>
> >> 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 ?

It does, but does it as test_and_set and then clear if error as we do in
other drivers.

-- 
Gustavo F. Padovan
http://profusion.mobi
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