linux-kernel - Re: [PATCH] HID: apple: Add support for magic keyboard backlight on T2 Macs

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Message-Id: <B28CFBDD-16ED-41AE-AE4A-92066D0DD4D8@gmail.com>
Date: Tue, 2 Jul 2024 08:57:23 +1000
From: Orlando Chamberlain <orlandoch.dev@...il.com>
To: Aditya Garg <gargaditya08@...e.com>
Cc: Jiri Kosina <jikos@...nel.org>, bentiss@...nel.org,
 linux-input@...r.kernel.org,
 Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] HID: apple: Add support for magic keyboard backlight on T2 Macs



> On 2 Jul 2024, at 8:48 AM, Orlando Chamberlain <orlandoch.dev@...il.com> wrote:
> 
>> On 2 Jul 2024, at 4:19 AM, Aditya Garg <gargaditya08@...e.com> wrote:
>> Apparently this patch is breaking touchbar functionality is some cases.
> 
> I think this is because apple_magic_backlight_init will return an error when it finds the touchbar interface, but this return value is not checked, so hid-apple still binds to the touchbar backlight.

We may also need to make sure hid_hw_stop is called in this case. Perhaps we can move this logic from apple_magic_backlight_init to apple_probe?

> 
> This should be fixable so I don't think we need to still have the separate driver.
> 
>>> 
>>> static int apple_probe(struct hid_device *hdev,
>>>      const struct hid_device_id *id)
>>> {
>>> @@ -860,6 +940,9 @@ static int apple_probe(struct hid_device *hdev,
>>>  if (quirks & APPLE_BACKLIGHT_CTL)
>>>      apple_backlight_init(hdev);
>>> 
>>> +    if (quirks & APPLE_MAGIC_BACKLIGHT)
>>> +        apple_magic_backlight_init(hdev);
> 
> return value isn't checked here ^, we return 0 unconditionally below.
> 
>>> +
>>>  return 0;
>>> }