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From: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date: Thu, 7 Sep 2017 17:15:08 +0300
Message-ID: <CABBYNZLOCkKnPU0HBkDSwJgus7fwXV80yreET1zG+qF7-oy+rg@mail.gmail.com>
Subject: Re: Bluetooth LE battery reporting?
To: Bastien Nocera <hadess@hadess.net>
Cc: Marcel Holtmann <marcel@holtmann.org>, Szymon Janc <szymon.janc@codecoup.pl>,
	Bluez mailing list <linux-bluetooth@vger.kernel.org>
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List-ID: <linux-bluetooth.vger.kernel.org>

Hi Bastien,

On Thu, Sep 7, 2017 at 5:03 PM, Bastien Nocera <hadess@hadess.net> wrote:
> On Thu, 2017-09-07 at 01:16 +0200, Bastien Nocera wrote:
>> On Wed, 2017-09-06 at 16:37 +0200, Bastien Nocera wrote:
>> > On Wed, 2017-09-06 at 10:40 +0200, Marcel Holtmann wrote:
>> > >
>> >
>> > <snip>
>> > > I assumed that it is forbidden to include HID battery reporting
>> > > events via the GATT HID descriptors. I think the standard clearly
>> > > says these have to come via battery service and not via HID.
>> >
>> > So we're back to implementing battery reporting as a separate
>> > profile.
>> > What would be a good example/skeleton to use to implement this?
>>
>> This is what I managed to do so far:
>> https://github.com/hadess/bluez/commits/ble-battery
>>
>> A first (gentle) pass at a review would be nice, especially if
>> there's
>> a better way to get notifications on both the attributes in one go.
>
> Obviously, the reworked code I wrote at 1 AM didn't work correctly.
> I've fixed the copy/paste bugs and pushed it.
>
>> The second question is how I would export this.
>>
>> I'm currently thinking that exporting a new interface on the device
>> itself might be the best idea, and I'll monitor devices directly in
>> UPower to export them to desktops. Would that be a good way?
>
> Still unsure about this, comments welcome.
>
>> And as UPower will be the likely consumer of this data, I think I'll
>> try mapping this set of flags:
>> https://www.bluetooth.com/specifications/gatt/viewer?attributeXmlFile
>> =org.bluetooth.characteristic.battery_power_state.xml
>> to UPower properties rather than trying to export it as-is.
>
> I've written parsing code for this. Does anyone know of a device which
> would use the Battery Power State characteristic so I could try it out?
>
> Finally, I've realised that my code replicates a lot of the code in
> bas.[ch], which is only used by the hog profile plugin. Seeing as this
> does nothing (the Battery Level is at the same level as the HoG
> characteristics, not a child of it), I've removed it.

We should probably make similar changes to what was done in dis.c so
it can operate with gatt_db directly instead of doing its own
discovery.

-- 
Luiz Augusto von Dentz