Re: [PATCH v3 1/9] HID: hid-appletb-bl: add driver for the backlight of Apple Touch Bars

Aditya Garg
2024-08-10T13:23:39Z

Hi Thomas

>
>> diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile
>> index e40f1ddeb..1d825a474 100644
>> --- a/drivers/hid/Makefile
>> +++ b/drivers/hid/Makefile
>> @@ -29,6 +29,7 @@ obj-$(CONFIG_HID_ALPS) += hid-alps.o
>> obj-$(CONFIG_HID_ACRUX) += hid-axff.o
>> obj-$(CONFIG_HID_APPLE) += hid-apple.o
>> obj-$(CONFIG_HID_APPLEIR) += hid-appleir.o
>> +obj-$(CONFIG_HID_APPLETB_BL) += hid-appletb-bl.o
>> obj-$(CONFIG_HID_CREATIVE_SB0540) += hid-creative-sb0540.o
>> obj-$(CONFIG_HID_ASUS) += hid-asus.o
>> obj-$(CONFIG_HID_AUREAL) += hid-aureal.o
>> diff --git a/drivers/hid/hid-appletb-bl.c b/drivers/hid/hid-appletb-bl.c
>> new file mode 100644
>> index 000000000..00bbe45df
>> --- /dev/null
>> +++ b/drivers/hid/hid-appletb-bl.c
>> @@ -0,0 +1,206 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Apple Touch Bar Backlight Driver
>> + *
>> + * Copyright (c) 2017-2018 Ronald Tschalär
>> + * Copyright (c) 2022-2023 Kerem Karabay <kekrby@gmail.com>
>> + */
>> +
>> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>
> This is unused.
>
> #include <linux/device.h>

Can you clarify what you mean here?
>
>> +#include <linux/hid.h>
>> +#include <linux/backlight.h>
>> +
>> +#include "hid-ids.h"
>> +
>> +#define APPLETB_BL_ON 1
>> +#define APPLETB_BL_DIM 3
>> +#define APPLETB_BL_OFF 4
>> +
>> +#define HID_UP_APPLEVENDOR_TB_BL 0xff120000
>> +
>> +#define HID_VD_APPLE_TB_BRIGHTNESS 0xff120001
>> +#define HID_USAGE_AUX1 0xff120020
>> +#define HID_USAGE_BRIGHTNESS 0xff120021
>> +
>> +static int appletb_bl_def_brightness = 2;
>> +module_param_named(brightness, appletb_bl_def_brightness, int, 0444);
>> +MODULE_PARM_DESC(brightness, "Default brightness:\n"
>> + " 0 - Touchbar is off\n"
>> + " 1 - Dim brightness\n"
>> + " [2] - Full brightness");
>> +
>> +struct appletb_bl {
>> + struct hid_field *aux1_field, *brightness_field;
>> + struct backlight_device *bdev;
>> +
>> + bool full_on;
>> +};
>> +
>> +const u8 appletb_bl_brightness_map[] = {
>
> static?
>
>> + APPLETB_BL_OFF,
>> + APPLETB_BL_DIM,
>> + APPLETB_BL_ON
>
> The last element is not a sentinel element, so it should have comma.

static const u8 appletb_bl_brightness_map[] = {
APPLETB_BL_OFF,
APPLETB_BL_DIM,
APPLETB_BL_ON,
};

This?
>
>> +};
>> +
>> +static int appletb_bl_set_brightness(struct appletb_bl *bl, u8 brightness)
>> +{
>> + struct hid_report *report = bl->brightness_field->report;
>> + struct hid_device *hdev = report->device;
>> + int ret;
>> +
>> + ret = hid_set_field(bl->aux1_field, 0, 1);
>> + if (ret) {
>> + hid_err(hdev, "Failed to set auxiliary field (%pe)\n", ERR_PTR(ret));
>> + return ret;
>> + }
>> +
>> + ret = hid_set_field(bl->brightness_field, 0, brightness);
>> + if (ret) {
>> + hid_err(hdev, "Failed to set brightness field (%pe)\n", ERR_PTR(ret));
>> + return ret;
>> + }
>> +
>> + if (!bl->full_on) {
>> + ret = hid_hw_power(hdev, PM_HINT_FULLON);
>> + if (ret < 0) {
>> + hid_err(hdev, "Device didn't power on (%pe)\n", ERR_PTR(ret));
>> + return ret;
>> + }
>> +
>> + bl->full_on = true;
>> + }
>> +
>> + hid_hw_request(hdev, report, HID_REQ_SET_REPORT);
>> +
>> + if (brightness == APPLETB_BL_OFF) {
>> + hid_hw_power(hdev, PM_HINT_NORMAL);
>> + bl->full_on = false;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static int appletb_bl_update_status(struct backlight_device *bdev)
>> +{
>> + struct appletb_bl *bl = bl_get_data(bdev);
>> + u16 brightness;
>> +
>> + if (bdev->props.state & BL_CORE_SUSPENDED)
>> + brightness = 0;
>
> From backlight.h:
>
> * backlight drivers are expected to use backlight_is_blank()
> * in their update_status() operation rather than reading the
> * state property.
>
> Seems to be applicable here.
>
> Also the hardcoded "0" as index into appletb_bl_brightness_map could be
> avoided by some restructuring.

static int appletb_bl_update_status(struct backlight_device *bdev)
{
struct appletb_bl *bl = bl_get_data(bdev);
u16 brightness;

if (backlight_is_blank(bdev))
brightness = APPLETB_BL_OFF;
else
brightness = backlight_get_brightness(bdev);

return appletb_bl_set_brightness(bl, appletb_bl_brightness_map[brightness]);
}

This?
>
>> + else
>> + brightness = backlight_get_brightness(bdev);
>> +
>> + return appletb_bl_set_brightness(bl, appletb_bl_brightness_map[brightness]);
>> +}
>> +
>> +static const struct backlight_ops appletb_bl_backlight_ops = {
>> + .options = BL_CORE_SUSPENDRESUME,
>> + .update_status = appletb_bl_update_status,
>> +};
>> +
>> +static int appletb_bl_probe(struct hid_device *hdev, const struct hid_device_id *id)
>> +{
>> + struct hid_field *aux1_field, *brightness_field;
>> + struct backlight_properties bl_props = { 0 };
>> + struct device *dev = &hdev->dev;
>> + struct appletb_bl *bl;
>> + int ret;
>> +
>> + ret = hid_parse(hdev);
>> + if (ret)
>> + return dev_err_probe(dev, ret, "HID parse failed\n");
>> +
>> + aux1_field = hid_find_field(hdev, HID_FEATURE_REPORT,
>> + HID_VD_APPLE_TB_BRIGHTNESS, HID_USAGE_AUX1);
>> +
>> + brightness_field = hid_find_field(hdev, HID_FEATURE_REPORT,
>> + HID_VD_APPLE_TB_BRIGHTNESS, HID_USAGE_BRIGHTNESS);
>> +
>> + if (!aux1_field || !brightness_field)
>> + return -ENODEV;
>> +
>> + if (aux1_field->report != brightness_field->report)
>> + return dev_err_probe(dev, -ENODEV, "Encountered unexpected report structure\n");
>> +
>> + bl = devm_kzalloc(dev, sizeof(*bl), GFP_KERNEL);
>> + if (!bl)
>> + return -ENOMEM;
>> +
>> + ret = hid_hw_start(hdev, HID_CONNECT_DRIVER);
>> + if (ret)
>> + return dev_err_probe(dev, ret, "HID hardware start failed\n");
>> +
>> + ret = hid_hw_open(hdev);
>> + if (ret) {
>> + dev_err_probe(dev, ret, "HID hardware open failed\n");
>> + goto stop_hw;
>> + }
>> +
>> + bl->aux1_field = aux1_field;
>> + bl->brightness_field = brightness_field;
>> +
>> + if (appletb_bl_def_brightness == 0)
>> + ret = appletb_bl_set_brightness(bl, APPLETB_BL_OFF);
>> + else if (appletb_bl_def_brightness == 1)
>> + ret = appletb_bl_set_brightness(bl, APPLETB_BL_DIM);
>> + else
>> + ret = appletb_bl_set_brightness(bl, APPLETB_BL_ON);
>> +
>> + if (ret) {
>> + dev_err_probe(dev, ret, "Failed to set touch bar brightness to off\n");
>> + goto close_hw;
>> + }
>> +
>> + bl_props.type = BACKLIGHT_RAW;
>> + bl_props.max_brightness = ARRAY_SIZE(appletb_bl_brightness_map) - 1;
>> +
>> + bl->bdev = devm_backlight_device_register(dev, "appletb_backlight", dev, bl,
>> + &appletb_bl_backlight_ops, &bl_props);
>> + if (IS_ERR(bl->bdev)) {
>> + ret = PTR_ERR(bl->bdev);
>> + dev_err_probe(dev, ret, "Failed to register backlight device\n");
>> + goto close_hw;
>> + }
>> +
>> + hid_set_drvdata(hdev, bl);
>> +
>> + return 0;
>> +
>> +close_hw:
>> + hid_hw_close(hdev);
>> +stop_hw:
>> + hid_hw_stop(hdev);
>> +
>> + return ret;
>> +}
>> +
>> +static void appletb_bl_remove(struct hid_device *hdev)
>> +{
>> + struct appletb_bl *bl = hid_get_drvdata(hdev);
>> +
>> + appletb_bl_set_brightness(bl, APPLETB_BL_OFF);
>> +
>> + hid_hw_close(hdev);
>> + hid_hw_stop(hdev);
>> +}
>> +
>> +static const struct hid_device_id appletb_bl_hid_ids[] = {
>> + /* MacBook Pro's 2018, 2019, with T2 chip: iBridge DFR Brightness */
>> + { HID_USB_DEVICE(USB_VENDOR_ID_APPLE, USB_DEVICE_ID_APPLE_TOUCHBAR_BACKLIGHT) },
>> + { }
>> +};
>> +MODULE_DEVICE_TABLE(hid, appletb_bl_hid_ids);
>> +
>> +static struct hid_driver appletb_bl_hid_driver = {
>> + .name = "hid-appletb-bl",
>> + .id_table = appletb_bl_hid_ids,
>> + .probe = appletb_bl_probe,
>> + .remove = appletb_bl_remove,
>> +};
>> +module_hid_driver(appletb_bl_hid_driver);
>> +
>> +MODULE_AUTHOR("Ronald Tschalär");
>> +MODULE_AUTHOR("Kerem Karabay <kekrby@gmail.com>");
>> +MODULE_DESCRIPTION("MacBookPro Touch Bar Backlight Driver");
>> +MODULE_LICENSE("GPL");
>
> <snip>

Thanks
Aditya