linux-kernel - Re: [PATCH RESEND v2 1/4] HID: hid-appletb-bl: add driver for the backlight of Apple Touch Bars

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Message-ID:
 <PN0PR01MB8288DA05B1DEE461C605348DB8F72@PN0PR01MB8288.INDPRD01.PROD.OUTLOOK.COM>
Date: Wed, 5 Feb 2025 03:50:17 +0000
From: Aditya Garg <gargaditya08@...e.com>
To: Jiri Kosina <jikos@...nel.org>
CC: "bentiss@...nel.org" <bentiss@...nel.org>, Benjamin Tissoires
	<benjamin.tissoires@...hat.com>, Thomas Weißschuh
	<linux@...ssschuh.net>, Thomas Weißschuh
	<thomas@...ch.de>, Kerem Karabay <kekrby@...il.com>, Orlando Chamberlain
	<orlandoch.dev@...il.com>, Linux Kernel Mailing List
	<linux-kernel@...r.kernel.org>, "linux-input@...r.kernel.org"
	<linux-input@...r.kernel.org>
Subject: Re: [PATCH RESEND v2 1/4] HID: hid-appletb-bl: add driver for the
 backlight of Apple Touch Bars



> On 4 Feb 2025, at 7:47 AM, Jiri Kosina <jikos@...nel.org> wrote:
> 
> On Tue, 4 Feb 2025, Aditya Garg wrote:
> 
>> You might have noticed that the hid-apple driver has code for the magic
>> backlight. Now we have a case of MacBook Air 2020, which does not have a
>> touchbar but still shows presence of the touchbar backlight device, just
>> because it needs it for the keyboard backlight. In case we merge both
>> the backlight and touchbar code in a driver, on that model, the
>> backlight breaks. If kept separate, the touchbar driver simply doesn't
>> load and backlight works.
> 
> Sorry for being dense, but does that mean that it's either hid-appletb-bl
> or hid-apple, but never both to make a good user experience on those
> devices?
> 
> If so, can you please point out what exactly is the reason?
> 
> Either those have different VID/PID combination, and then it can be easily
> made conditional both in code and in runtime.
> Are we talking about conflicting VID/PID combinations, some of them
> needing current hid-apple, and some of them needing (in a mutually
> exclusive way) hid-appletb-bl?
> 

Just to clarify a bit more,

The touchbar backlight device is 05ac:8102, in all the models with magic backlight, that is, with as well as without touchbar. The MacBook Air 2020 is the only model with this device but not having a touchbar.

This device is responsible for both the touchbar brightness and the keyboard backlight, the 0th interface being responsible for keyboard backlight on Air and 1st on others.
> Thanks,
> 
> --
> Jiri Kosina
> SUSE Labs
>