Message-ID: <AB53350C-19E2-45EB-B4D5-001411D0536D@live.com>
Date: Wed, 3 Jul 2024 17:53:10 +0000
From: Aditya Garg <gargaditya08@...e.com>
To: Benjamin Tissoires <bentiss@...nel.org>
CC: Jiri Kosina <jikos@...nel.org>, Orlando Chamberlain
	<orlandoch.dev@...il.com>, "linux-input@...r.kernel.org"
	<linux-input@...r.kernel.org>, Linux Kernel Mailing List
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] HID: apple: Add support for magic keyboard backlight
 on T2 Macs



> On 3 Jul 2024, at 10:40 PM, Benjamin Tissoires <bentiss@...nel.org> wrote:
> 
> On Jul 03 2024, Aditya Garg wrote:
>> 
>> Hi Benjamin
>> 
>>> On 3 Jul 2024, at 7:38 PM, Benjamin Tissoires <bentiss@...nel.org> wrote:
>>> 
>>> On Jul 03 2024, Aditya Garg wrote:
>>>> From: Orlando Chamberlain <orlandoch.dev@...il.com>
>>>> 
>>>> Unlike T2 Macs with Butterfly keyboard, who have their keyboard backlight
>>>> on the USB device the T2 Macs with Magic keyboard have their backlight on
>>>> the Touchbar backlight device (05ac:8102).
>>>> 
>>>> Support for Butterfly keyboards has already been added in 9018eacbe623
>>>> ("HID: apple: Add support for keyboard backlight on certain T2 Macs.").
>>>> This patch adds support for the Magic keyboards.
>>>> 
>>>> Co-developed-by: Aditya Garg <gargaditya08@...e.com>
>>>> Signed-off-by: Aditya Garg <gargaditya08@...e.com>
>>>> Signed-off-by: Orlando Chamberlain <orlandoch.dev@...il.com>
>>> 
>>> Nitpick: the ordering of the signed-off is weird. It should be in order
>>> of persons who touched this driver.
>>> 
>>> Given that the From is Orlando and Aditya is submitting, I would have
>>> expected Orlando, then Aditya…
>>> 
>> 
>> Will fix this.
>> 
>>>> ---
>>>> drivers/hid/hid-apple.c | 87 ++++++++++++++++++++++++++++++++++++++++-
>>>> 1 file changed, 86 insertions(+), 1 deletion(-)
>>>> 
>>>> diff --git a/drivers/hid/hid-apple.c b/drivers/hid/hid-apple.c
>>>> index bd022e004356..2d1cd4456303 100644
>>>> --- a/drivers/hid/hid-apple.c
>>>> +++ b/drivers/hid/hid-apple.c
>>>> @@ -8,6 +8,8 @@
>>>> *  Copyright (c) 2006-2007 Jiri Kosina
>>>> *  Copyright (c) 2008 Jiri Slaby <jirislaby@...il.com>
>>>> *  Copyright (c) 2019 Paul Pawlowski <paul@...rm.io>
>>>> + *  Copyright (c) 2023 Orlando Chamberlain <orlandoch.dev@...il.com>
>>>> + *  Copyright (c) 2024 Aditya Garg <gargaditya08@...e.com>
>>>> */
>>>> 
>>>> /*
>>>> @@ -23,6 +25,7 @@
>>>> #include <linux/timer.h>
>>>> #include <linux/string.h>
>>>> #include <linux/leds.h>
>>>> +#include <dt-bindings/leds/common.h>
>>>> 
>>>> #include "hid-ids.h"
>>>> 
>>>> @@ -37,13 +40,18 @@
>>>> #define APPLE_NUMLOCK_EMULATION BIT(8)
>>>> #define APPLE_RDESC_BATTERY BIT(9)
>>>> #define APPLE_BACKLIGHT_CTL BIT(10)
>>>> -#define APPLE_IS_NON_APPLE BIT(11)
>>>> +#define APPLE_MAGIC_BACKLIGHT BIT(11)
>>>> +#define APPLE_IS_NON_APPLE BIT(12)
>>> 
>>> Please keep existing quirks definition in place, it adds noise for
>>> nothing in the patch. Also, technically, these quirks are used in
>>> .driver_data so they are uapi.
>>> 
>> 
>> Sure
>> 
>>>> 
>>>> #define APPLE_FLAG_FKEY 0x01
>>>> 
>>>> #define HID_COUNTRY_INTERNATIONAL_ISO 13
>>>> #define APPLE_BATTERY_TIMEOUT_MS 60000
>>>> 
>>>> +#define HID_USAGE_MAGIC_BL 0xff00000f
>>>> +#define APPLE_MAGIC_REPORT_ID_POWER 3
>>>> +#define APPLE_MAGIC_REPORT_ID_BRIGHTNESS 1
>>>> +
>>>> static unsigned int fnmode = 3;
>>>> module_param(fnmode, uint, 0644);
>>>> MODULE_PARM_DESC(fnmode, "Mode of fn key on Apple keyboards (0 = disabled, "
>>>> @@ -81,6 +89,12 @@ struct apple_sc_backlight {
>>>> struct hid_device *hdev;
>>>> };
>>>> 
>>>> +struct apple_magic_backlight {
>>>> + struct led_classdev cdev;
>>>> + struct hid_report *brightness;
>>>> + struct hid_report *power;
>>>> +};
>>>> +
>>>> struct apple_sc {
>>>> struct hid_device *hdev;
>>>> unsigned long quirks;
>>>> @@ -822,6 +836,66 @@ static int apple_backlight_init(struct hid_device *hdev)
>>>> return ret;
>>>> }
>>>> 
>>>> +static void apple_magic_backlight_report_set(struct hid_report *rep, s32 value, u8 rate)
>>>> +{
>>>> + rep->field[0]->value[0] = value;
>>>> + rep->field[1]->value[0] = 0x5e; /* Mimic Windows */
>>>> + rep->field[1]->value[0] |= rate << 8;
>>>> +
>>>> + hid_hw_request(rep->device, rep, HID_REQ_SET_REPORT);
>>>> +}
>>>> +
>>>> +static void apple_magic_backlight_set(struct apple_magic_backlight *backlight,
>>>> +      int brightness, char rate)
>>>> +{
>>>> + apple_magic_backlight_report_set(backlight->power, brightness ? 1 : 0, rate);
>>>> + if (brightness)
>>>> + apple_magic_backlight_report_set(backlight->brightness, brightness, rate);
>>>> +}
>>>> +
>>>> +static int apple_magic_backlight_led_set(struct led_classdev *led_cdev,
>>>> +  enum led_brightness brightness)
>>>> +{
>>>> + struct apple_magic_backlight *backlight = container_of(led_cdev,
>>>> + struct apple_magic_backlight, cdev);
>>>> +
>>>> + apple_magic_backlight_set(backlight, brightness, 1);
>>>> + return 0;
>>>> +}
>>>> +
>>>> +static int apple_magic_backlight_init(struct hid_device *hdev)
>>>> +{
>>>> + struct apple_magic_backlight *backlight;
>>>> +
>>>> + /*
>>>> +  * Ensure this usb endpoint is for the keyboard backlight, not touchbar
>>>> +  * backlight.
>>>> +  */
>>>> + if (hdev->collection[0].usage != HID_USAGE_MAGIC_BL)
>>>> + return -ENODEV;
>>>> +
>>>> + backlight = devm_kzalloc(&hdev->dev, sizeof(*backlight), GFP_KERNEL);
>>>> + if (!backlight)
>>>> + return -ENOMEM;
>>>> +
>>>> + backlight->brightness = hid_register_report(hdev, HID_FEATURE_REPORT,
>>>> + APPLE_MAGIC_REPORT_ID_BRIGHTNESS, 0);
>>>> + backlight->power = hid_register_report(hdev, HID_FEATURE_REPORT,
>>>> + APPLE_MAGIC_REPORT_ID_POWER, 0);
>>>> +
>>>> + if (!backlight->brightness || !backlight->power)
>>>> + return -ENODEV;
>>>> +
>>>> + backlight->cdev.name = ":white:" LED_FUNCTION_KBD_BACKLIGHT;
>>>> + backlight->cdev.max_brightness = backlight->brightness->field[0]->logical_maximum;
>>> 
>>> This is weird: a few lines above, you register a new report with
>>> hid_register_report() and now you are directly accessing
>>> field[0]->logical_maximum in that new report, which should be set to 0.
>>> 
>>> Unless you are using hid_register_report() to retrieve an existing
>>> report, which is bending the API a bit but is OK, but you should at
>>> least check that report->size is > 0 (and put a comment that the reports
>>> exist already).
>>> 
>>> (or do what is done in apple_fetch_battery() to retrieve the current
>>> report)
>>> 
>> 
>> Instead of 
>> 
>> if (!backlight->brightness || !backlight->power)
>> return -ENODEV;
>> 
>> Should I do (will all proper whitespace and line formatting):
>> 
>> if (!backlight->brightness ||
>>             backlight->brightness->size == 0 ||
>>            !backlight->power ||
>>             backlight->power->size == 0)
>> return -ENODEV;
> 
> That, or:
> struct hid_report_enum *report_enum;
> 
> report_enum = &hdev->report_enum[HID_FEATURE_REPORT];
> backlight->brightness = report_enum->report_id_hash[APPLE_MAGIC_REPORT_ID_BRIGHTNESS];
> backlight->power = report_enum->report_id_hash[APPLE_MAGIC_REPORT_ID_POWER];
> 
> and then keep your "if (!backlight->brightness || !backlight->power)"

Lets go with this.

Sending a v3. Thanks for the help!
> 
>> 
>>> 
>>>> + backlight->cdev.brightness_set_blocking = apple_magic_backlight_led_set;
>>>> +
>>>> + apple_magic_backlight_set(backlight, 0, 0);
>>>> +
>>>> + return devm_led_classdev_register(&hdev->dev, &backlight->cdev);
>>>> +
>>>> +}
>>>> +
>>>> static int apple_probe(struct hid_device *hdev,
>>>> const struct hid_device_id *id)
>>>> {
>>>> @@ -860,6 +934,15 @@ static int apple_probe(struct hid_device *hdev,
>>>> if (quirks & APPLE_BACKLIGHT_CTL)
>>>> apple_backlight_init(hdev);
>>>> 
>>>> + if (quirks & APPLE_MAGIC_BACKLIGHT) {
>>>> + ret = apple_magic_backlight_init(hdev);
>>>> + if (ret) {
>>>> + del_timer_sync(&asc->battery_timer);
>>>> + hid_hw_stop(hdev);
>>>> + return ret;
>>> 
>>> Instead of manually unwind the probe in each sub-quirk, please add a new
>>> goto label and do goto out_err;
>> 
>> You mean this?:
> 
> yep. This way, if we get to add new quirks later, we can rely on this.
> 
>> 
>> if (quirks & APPLE_MAGIC_BACKLIGHT) {
>> ret = apple_magic_backlight_init(hdev);
>> if (ret)
>> goto out_err;
>> }
>> 
>> return 0;
>> 
>> out_err:
>> del_timer_sync(&asc->battery_timer);
>> hid_hw_stop(hdev);
>> return ret;
>> }
>> 
>> 
>>> 
>>>> + }
>>>> + }
>>>> +
>>>> return 0;
>>>> }
>>>> 
>>>> @@ -1073,6 +1156,8 @@ static const struct hid_device_id apple_devices[] = {
>>>> .driver_data = APPLE_HAS_FN | APPLE_ISO_TILDE_QUIRK | APPLE_RDESC_BATTERY },
>>>> { HID_BLUETOOTH_DEVICE(BT_VENDOR_ID_APPLE, USB_DEVICE_ID_APPLE_MAGIC_KEYBOARD_NUMPAD_2021),
>>>> .driver_data = APPLE_HAS_FN | APPLE_ISO_TILDE_QUIRK },
>>>> + { HID_USB_DEVICE(USB_VENDOR_ID_APPLE, USB_DEVICE_ID_APPLE_TOUCHBAR_BACKLIGHT),
>>>> + .driver_data = APPLE_MAGIC_BACKLIGHT },
>>>> 
>>>> { }
>>>> };
>>>> -- 
>>>> 2.45.2
>>>> 
>>> 
>>> Other than those few nitpicks, patch looks good. Please roll a v3 and
>>> I'll apply it.
>>> 
>>> Cheers,
>>> Benjamin
>> 
>> 
> 
> Cheers,
> Benjamin

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