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

Thomas Weißschuh
2024-08-10T12:16:11Z

On 2024-08-08 13:50:33+0000, Aditya Garg wrote:
> From: Kerem Karabay <kekrby@gmail.com>
>
> This commit adds a driver for the backlight of Apple Touch Bars on x86
> Macs. Note that currently only T2 Macs are supported.
>
> This driver is based on previous work done by Ronald Tschalär
> <ronald@innovation.ch>.
>
> Signed-off-by: Kerem Karabay <kekrby@gmail.com>
> Co-developed-by: Aditya Garg <gargaditya08@live.com>
> Signed-off-by: Aditya Garg <gargaditya08@live.com>
> ---
> MAINTAINERS | 6 +
> drivers/hid/Kconfig | 10 ++
> drivers/hid/Makefile | 1 +
> drivers/hid/hid-appletb-bl.c | 206 +++++++++++++++++++++++++++++++++++
> drivers/hid/hid-quirks.c | 4 +-
> 5 files changed, 226 insertions(+), 1 deletion(-)
> create mode 100644 drivers/hid/hid-appletb-bl.c
>

<snip>

> 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>

> +#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 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.

> + 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>