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From:   Aditya Garg <gargaditya08@live.com>
To:     "jikos@kernel.org" <jikos@kernel.org>,
        "benjamin.tissoires@redhat.com" <benjamin.tissoires@redhat.com>,
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CC:     "paul@mrarm.io" <paul@mrarm.io>, Aun-Ali Zaidi <admin@kodeit.net>,
        Orlando Chamberlain <redecorating@protonmail.com>
Subject: [PATCH 1/3] Add support for keyboard backlight on certain T2 Macs.
Thread-Topic: [PATCH 1/3] Add support for keyboard backlight on certain T2
 Macs.
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Date:   Fri, 21 Jan 2022 08:21:22 +0000
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From: Paul Pawlowski <paul@mrarm.io>

This patch introduces the requisite plumbing for supporting keyboard
backlight on T2-attached, USB exposed models. The quirk mechanism was
used to reuse the existing hid-apple driver.

Signed-off-by: Paul Pawlowski <paul@mrarm.io>
Signed-off-by: Aun-Ali Zaidi <admin@kodeit.net>
Signed-off-by: Aditya Garg <gargaditya08@live.com>
---
 drivers/hid/hid-apple.c | 125 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 125 insertions(+)

diff --git a/drivers/hid/hid-apple.c b/drivers/hid/hid-apple.c
index 24802a4a6..c22d445a9 100644
--- a/drivers/hid/hid-apple.c
+++ b/drivers/hid/hid-apple.c
@@ -7,6 +7,7 @@
  *  Copyright (c) 2005 Michael Haboustak <mike-@cinci.rr.com> for Concept2=
, Inc
  *  Copyright (c) 2006-2007 Jiri Kosina
  *  Copyright (c) 2008 Jiri Slaby <jirislaby@gmail.com>
+ *  Copyright (c) 2019 Paul Pawlowski <paul@mrarm.io>
  */
=20
 /*
@@ -33,6 +34,7 @@
 /* BIT(7) reserved, was: APPLE_IGNORE_HIDINPUT */
 #define APPLE_NUMLOCK_EMULATION	BIT(8)
 #define APPLE_RDESC_BATTERY	BIT(9)
+#define APPLE_BACKLIGHT_CTL	0x0200
=20
 #define APPLE_FLAG_FKEY		0x01
=20
@@ -61,6 +63,12 @@ MODULE_PARM_DESC(swap_fn_leftctrl, "Swap the Fn and left=
 Control keys. "
 		"(For people who want to keep PC keyboard muscle memory. "
 		"[0] =3D as-is, Mac layout, 1 =3D swapped, PC layout)");
=20
+struct apple_sc_backlight {
+	struct led_classdev cdev;
+	struct hid_device *hdev;
+	unsigned short backlight_off, backlight_on_min, backlight_on_max;
+};
+
 struct apple_sc {
 	struct hid_device *hdev;
 	unsigned long quirks;
@@ -68,6 +76,7 @@ struct apple_sc {
 	unsigned int fn_found;
 	DECLARE_BITMAP(pressed_numlock, KEY_CNT);
 	struct timer_list battery_timer;
+	struct apple_sc_backlight *backlight;
 };
=20
 struct apple_key_translation {
@@ -76,6 +85,20 @@ struct apple_key_translation {
 	u8 flags;
 };
=20
+struct apple_backlight_config_report {
+	u8 report_id;
+	u8 version;
+	u16 backlight_off, backlight_on_min, backlight_on_max;
+};
+
+struct apple_backlight_set_report {
+	u8 report_id;
+	u8 version;
+	u16 backlight;
+	u16 rate;
+};
+
+
 static const struct apple_key_translation apple2021_fn_keys[] =3D {
 	{ KEY_BACKSPACE, KEY_DELETE },
 	{ KEY_ENTER,	KEY_INSERT },
@@ -530,6 +553,105 @@ static int apple_input_configured(struct hid_device *=
hdev,
 	return 0;
 }
=20
+static bool apple_backlight_check_support(struct hid_device *hdev)
+{
+	int i;
+	unsigned int hid;
+	struct hid_report *report;
+
+	list_for_each_entry(report, &hdev->report_enum[HID_INPUT_REPORT].report_l=
ist, list) {
+		for (i =3D 0; i < report->maxfield; i++) {
+			hid =3D report->field[i]->usage->hid;
+			if ((hid & HID_USAGE_PAGE) =3D=3D HID_UP_MSVENDOR && (hid & HID_USAGE) =
=3D=3D 0xf)
+				return true;
+		}
+	}
+
+	return false;
+}
+
+static int apple_backlight_set(struct hid_device *hdev, u16 value, u16 rat=
e)
+{
+	int ret =3D 0;
+	struct apple_backlight_set_report *rep;
+
+	rep =3D kmalloc(sizeof(*rep), GFP_KERNEL);
+	if (rep =3D=3D NULL)
+		return -ENOMEM;
+
+	rep->report_id =3D 0xB0;
+	rep->version =3D 1;
+	rep->backlight =3D value;
+	rep->rate =3D rate;
+
+	ret =3D hid_hw_raw_request(hdev, 0xB0u, (u8 *) rep, sizeof(*rep),
+				 HID_OUTPUT_REPORT, HID_REQ_SET_REPORT);
+
+	kfree(rep);
+	return ret;
+}
+
+static int apple_backlight_led_set(struct led_classdev *led_cdev,
+	enum led_brightness brightness)
+{
+	struct apple_sc_backlight *backlight =3D container_of(led_cdev,
+							    struct apple_sc_backlight, cdev);
+
+	return apple_backlight_set(backlight->hdev, brightness, 0);
+}
+
+static int apple_backlight_init(struct hid_device *hdev)
+{
+	int ret;
+	struct apple_sc *asc =3D hid_get_drvdata(hdev);
+	struct apple_backlight_config_report *rep;
+
+	if (!apple_backlight_check_support(hdev))
+		return -EINVAL;
+
+	rep =3D kmalloc(0x200, GFP_KERNEL);
+	if (rep =3D=3D NULL)
+		return -ENOMEM;
+
+	ret =3D hid_hw_raw_request(hdev, 0xBFu, (u8 *) rep, sizeof(*rep),
+				 HID_FEATURE_REPORT, HID_REQ_GET_REPORT);
+	if (ret < 0) {
+		hid_err(hdev, "backlight request failed: %d\n", ret);
+		goto cleanup_and_exit;
+	}
+	if (ret < 8 || rep->version !=3D 1) {
+		hid_err(hdev, "backlight config struct: bad version %i\n", rep->version)=
;
+		ret =3D -EINVAL;
+		goto cleanup_and_exit;
+	}
+
+	hid_dbg(hdev, "backlight config: off=3D%u, on_min=3D%u, on_max=3D%u\n",
+		rep->backlight_off, rep->backlight_on_min, rep->backlight_on_max);
+
+	asc->backlight =3D devm_kzalloc(&hdev->dev, sizeof(*asc->backlight), GFP_=
KERNEL);
+	if (!asc->backlight) {
+		ret =3D -ENOMEM;
+		goto cleanup_and_exit;
+	}
+
+	asc->backlight->hdev =3D hdev;
+	asc->backlight->cdev.name =3D "apple::kbd_backlight";
+	asc->backlight->cdev.max_brightness =3D rep->backlight_on_max;
+	asc->backlight->cdev.brightness_set_blocking =3D apple_backlight_led_set;
+
+	ret =3D apple_backlight_set(hdev, 0, 0);
+	if (ret < 0) {
+		hid_err(hdev, "backlight set request failed: %d\n", ret);
+		goto cleanup_and_exit;
+	}
+
+	ret =3D devm_led_classdev_register(&hdev->dev, &asc->backlight->cdev);
+
+cleanup_and_exit:
+	kfree(rep);
+	return ret;
+}
+
 static int apple_probe(struct hid_device *hdev,
 		const struct hid_device_id *id)
 {
@@ -565,6 +687,9 @@ static int apple_probe(struct hid_device *hdev,
 		  jiffies + msecs_to_jiffies(APPLE_BATTERY_TIMEOUT_MS));
 	apple_fetch_battery(hdev);
=20
+	if (quirks & APPLE_BACKLIGHT_CTL)
+		apple_backlight_init(hdev);
+
 	return 0;
 }
=20
--=20
2.25.1