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Date: Thu, 28 May 2015 08:48:32 -0600
Message-ID: <CAD8Lp44Au=AenfG9EnLAJJ8dw7kientAoKppEMh7U2wY73pSQg@mail.gmail.com>
Subject: Re: Realtek USB bluetooth: no scan results when wifi is connected
From: Daniel Drake <drake@endlessm.com>
To: Marcel Holtmann <marcel@holtmann.org>
Cc: =?UTF-8?B?6ZmI6Imz6JCN?= <champion_chen@realsil.com.cn>,
	Larry Finger <Larry.Finger@lwfinger.net>, Carlo Caione <carlo@endlessm.com>,
	Linux Bluetooth mailing list <linux-bluetooth@vger.kernel.org>,
	"shaofu@realtek.com > shaofu" <shaofu@realtek.com>, =?UTF-8?B?5byg5b+X56Wl?= <askijerry_zhang@realsil.com.cn>,
	=?UTF-8?B?6ZmG5pyx5Lyf?= <alex_lu@realsil.com.cn>,
	Chih-Hsiang Wang <wangchihhs@realtek.com>, =?UTF-8?B?5q+b5Li66ZSL?= <jason_mao@realsil.com.cn>,
	"pkshih@realtek.com" <pkshih@realtek.com>
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List-ID: <linux-bluetooth.vger.kernel.org>

On Thu, May 28, 2015 at 8:23 AM, Marcel Holtmann <marcel@holtmann.org> wrote:
> Hi Champion,
>
>>       We want to share some information between wifi driver and bt driver, what rules do you recommend for the following situation ?
>> 1. at system startup, bluetooth driver want to read some information (eg antenna settings) that generated by wifi , shall we use files or /proc/ information?
>> 2. when user is using Bluetooth, bt driver may notify wifi driver to perform better, shall we use socket to communication?
>
> this is the Bluetooth subsystem communicating with the WiFi subsystem (cfg80211) and vice versa, then this is happening inside the kernel. I do not see any need to even try to go via userspace at all. So neither /proc and no sockets for this.

I agree. But can we give more specific advice on how to do this inside
the kernel?
i.e. should they create a new driver under drivers/misc which exposes
a shared API via EXPORT_SYMBOL?

The other option for Realtek to consider is to do this in
hardware/firmware. I already saw that the btcoexist driver knows
exactly when the wifi and BT start and finish scanning, so there is
clearly already an information-passing mechanism between the two
interfaces. I wonder if an updated firmware could extend that to
include the new information that you wish to additionally transfer.

Daniel