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

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Message-ID:
 <PN3PR01MB9597026ED0B9D82EC13F4DD7B8C32@PN3PR01MB9597.INDPRD01.PROD.OUTLOOK.COM>
Date: Tue, 25 Feb 2025 10:01:16 +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 3:07 PM, Aditya Garg <gargaditya08@...e.com> wrote:
> 
> 
> 
>> 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?

Hmm, I got some docs about this, though not very clear, but good enough to make me decide to not include these two in the kconfig.

This also means that the driver can now be merged without pulling linux-next in DRM.