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Date:   Mon, 13 Apr 2020 18:52:06 +0200
From:   Pali =?utf-8?B?Um9ow6Fy?= <pali@kernel.org>
To:     Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc:     "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>,
        David Heidelberg <david@ixit.cz>
Subject: Re: [PATCH 1/3] src/profile: Distinguish between zero-set HFP AG
 features and unset HFP AG features
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On Monday 13 April 2020 09:44:14 Luiz Augusto von Dentz wrote:
> On Mon, Apr 13, 2020 at 9:25 AM Pali Rohár <pali@kernel.org> wrote:
> > @@ -1750,15 +1758,19 @@ static int ext_disconnect_dev(struct btd_service *service)
> >  static char *get_hfp_hf_record(struct ext_profile *ext, struct ext_io *l2cap,
> >                                                         struct ext_io *rfcomm)
> >  {
> > +       /* HFP 1.7.2: By default features bitfield is 0b000000 */
> >         return g_strdup_printf(HFP_HF_RECORD, rfcomm->chan, ext->version,
> > -                                               ext->name, ext->features);
> > +                               ext->name,
> > +                               ext->have_features ? ext->features : 0x0);
> >  }
> >
> >  static char *get_hfp_ag_record(struct ext_profile *ext, struct ext_io *l2cap,
> >                                                         struct ext_io *rfcomm)
> >  {
> > +       /* HFP 1.7.2: By default features bitfield is 0b001001 */
> >         return g_strdup_printf(HFP_AG_RECORD, rfcomm->chan, ext->version,
> > -                                               ext->name, ext->features);
> > +                               ext->name,
> > +                               ext->have_features ? ext->features : 0x9);
> 
> I wonder why you didn't just initialize the features wiht 0x9 instead
> of adding a flag to track it, btw add a define with value 0x09 like
> HFP_DEFAULT_FEATURES that way it is clearer why we are doing this.

This function get_hfp_ag_record() is for parsing local features. You are
right that for local features we do not need a flag to track it.

But flag for tracking is needed for parsing remote features. And to have
unified code for storing local and remote features it is easier to have
always a flag for checking if features were provided or not.

I can put these default values in profile-role specific macros e.g.:

#define HFP_AG_DEFAULT_FEATURES 0x09
#define HFP_HF_DEFAULT_FEATURES 0x00
#define HSP_HS_DEFAULT_VOLCNTRL "false"

Or do you prefer different names?