linux-kernel - Re: [PATCH v4 2/2] drm/tiny: add driver for Apple Touch Bars in x86 Macs

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Message-ID:
 <PN3PR01MB95976ED2D5FDC48C5F9E6EF7B8C32@PN3PR01MB9597.INDPRD01.PROD.OUTLOOK.COM>
Date: Tue, 25 Feb 2025 09:37:04 +0000
From: Aditya Garg <gargaditya08@...e.com>
To: Thomas Zimmermann <tzimmermann@...e.de>
CC: "maarten.lankhorst@...ux.intel.com" <maarten.lankhorst@...ux.intel.com>,
	"mripard@...nel.org" <mripard@...nel.org>, "airlied@...il.com"
	<airlied@...il.com>, "simona@...ll.ch" <simona@...ll.ch>,
	"andriy.shevchenko@...ux.intel.com" <andriy.shevchenko@...ux.intel.com>,
	Kerem Karabay <kekrby@...il.com>, Atharva Tiwari <evepolonium@...il.com>,
	Aun-Ali Zaidi <admin@...eit.net>, Linux Kernel Mailing List
	<linux-kernel@...r.kernel.org>, "dri-devel@...ts.freedesktop.org"
	<dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v4 2/2] drm/tiny: add driver for Apple Touch Bars in x86
 Macs



> On 25 Feb 2025, at 3:05 PM, Thomas Zimmermann <tzimmermann@...e.de> wrote:
> 
> Hi
> 
>> Am 25.02.25 um 10:07 schrieb Aditya Garg:
>> 
>>>> On 25 Feb 2025, at 2:34 PM, Aditya Garg <gargaditya08@...e.com> wrote:
>>> 
>>> 
>>> 
>>>> On 25 Feb 2025, at 1:27 PM, Thomas Zimmermann <tzimmermann@...e.de> wrote:
>>>> 
>>>> Hi
>>>> 
>>>> Am 24.02.25 um 17:58 schrieb Aditya Garg:
>>>> [...]
>>>>>> +config DRM_APPLETBDRM
>>>>>> +    tristate "DRM support for Apple Touch Bars"
>>>>>> +    depends on DRM && USB && MMU
>>>>>> +    select DRM_GEM_SHMEM_HELPER
>>>>>> +    select DRM_KMS_HELPER
>>>>>> +    select HID_APPLETB_BL
>>>>> Btw I have a doubt regarding this dependency. While hid-appletb-bl has made into the linux-next tree, it has still not been merged into Linus' tree, and neither the drm tree I assume. It potentially could cause issues?
>>>> Yes. We cannot merge this driver until we have this symbol in our tree. But that will happen sooner or later.
>>>> 
>>>> More problematic is that your driver selects HID_APPLETB_BL. From what I've seen, this symbol is user configurable, so the driver shouldn't select it. You need to use 'depends on' instead of 'select' here.
>>> Looking at this again, maybe it should be selected. If you see the kernel config of TINYDRM_HX8357D, which is also in drm/tiny, it is selecting BACKLIGHT_CLASS_DEVICE.
> 
> This driver does it wrong.
> 
>> To make things more clear,
>> 
>> 1. hid-appletb-bl is for the backlight of the touchbar. The DRM code remains separate.
>> 2. hid-multitouch is to make the touchbar a touch screen. You can still use the driver without the touch functionality.
> 
> If your driver does not require this, it shouldn't select or depend on it.

Could you explain me in what situations would select be used?