--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Keyboard backlight LED driver for the Wilco Embedded Controller
+ *
+ * Copyright 2019 Google LLC
+ *
+ * Since the EC will never change the backlight level of its own accord,
+ * we don't need to implement a brightness_get() method.
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/leds.h>
+#include <linux/platform_data/wilco-ec.h>
+#include <linux/slab.h>
+
+#define WILCO_EC_COMMAND_KBBL 0x75
+#define WILCO_KBBL_MODE_FLAG_PWM BIT(1) /* Set brightness by percent. */
+#define WILCO_KBBL_DEFAULT_BRIGHTNESS 0
+
+struct wilco_keyboard_leds {
+ struct wilco_ec_device *ec;
+ struct led_classdev keyboard;
+};
+
+enum wilco_kbbl_subcommand {
+ WILCO_KBBL_SUBCMD_GET_FEATURES = 0x00,
+ WILCO_KBBL_SUBCMD_GET_STATE = 0x01,
+ WILCO_KBBL_SUBCMD_SET_STATE = 0x02,
+};
+
+/**
+ * struct wilco_keyboard_leds_msg - Message to/from EC for keyboard LED control.
+ * @command: Always WILCO_EC_COMMAND_KBBL.
+ * @status: Set by EC to 0 on success, 0xFF on failure.
+ * @subcmd: One of enum wilco_kbbl_subcommand.
+ * @reserved3: Should be 0.
+ * @mode: Bit flags for used mode, we want to use WILCO_KBBL_MODE_FLAG_PWM.
+ * @reserved5to8: Should be 0.
+ * @percent: Brightness in 0-100. Only meaningful in PWM mode.
+ * @reserved10to15: Should be 0.
+ */
+struct wilco_keyboard_leds_msg {
+ u8 command;
+ u8 status;
+ u8 subcmd;
+ u8 reserved3;
+ u8 mode;
+ u8 reserved5to8[4];
+ u8 percent;
+ u8 reserved10to15[6];
+} __packed;
+
+/* Send a request, get a response, and check that the response is good. */
+static int send_kbbl_msg(struct wilco_ec_device *ec,
+ struct wilco_keyboard_leds_msg *request,
+ struct wilco_keyboard_leds_msg *response)
+{
+ struct wilco_ec_message msg;
+ int ret;
+
+ memset(&msg, 0, sizeof(msg));
+ msg.type = WILCO_EC_MSG_LEGACY;
+ msg.request_data = request;
+ msg.request_size = sizeof(*request);
+ msg.response_data = response;
+ msg.response_size = sizeof(*response);
+
+ ret = wilco_ec_mailbox(ec, &msg);
+ if (ret < 0) {
+ dev_err(ec->dev,
+ "Failed sending keyboard LEDs command: %d", ret);
+ return ret;
+ }
+
+ if (response->status) {
+ dev_err(ec->dev,
+ "EC reported failure sending keyboard LEDs command: %d",
+ response->status);
+ return -EIO;
+ }
+
+ return 0;
+}
+
+static int set_kbbl(struct wilco_ec_device *ec, enum led_brightness brightness)
+{
+ struct wilco_keyboard_leds_msg request;
+ struct wilco_keyboard_leds_msg response;
+
+ memset(&request, 0, sizeof(request));
+ request.command = WILCO_EC_COMMAND_KBBL;
+ request.subcmd = WILCO_KBBL_SUBCMD_SET_STATE;
+ request.mode = WILCO_KBBL_MODE_FLAG_PWM;
+ request.percent = brightness;
+
+ return send_kbbl_msg(ec, &request, &response);
+}
+
+static int kbbl_exist(struct wilco_ec_device *ec, bool *exists)
+{
+ struct wilco_keyboard_leds_msg request;
+ struct wilco_keyboard_leds_msg response;
+ int ret;
+
+ memset(&request, 0, sizeof(request));
+ request.command = WILCO_EC_COMMAND_KBBL;
+ request.subcmd = WILCO_KBBL_SUBCMD_GET_FEATURES;
+
+ ret = send_kbbl_msg(ec, &request, &response);
+ if (ret < 0)
+ return ret;
+
+ *exists = response.status != 0xFF;
+
+ return 0;
+}
+
+/**
+ * kbbl_init() - Initialize the state of the keyboard backlight.
+ * @ec: EC device to talk to.
+ *
+ * Gets the current brightness, ensuring that the BIOS already initialized the
+ * backlight to PWM mode. If not in PWM mode, then the current brightness is
+ * meaningless, so set the brightness to WILCO_KBBL_DEFAULT_BRIGHTNESS.
+ *
+ * Return: Final brightness of the keyboard, or negative error code on failure.
+ */
+static int kbbl_init(struct wilco_ec_device *ec)
+{
+ struct wilco_keyboard_leds_msg request;
+ struct wilco_keyboard_leds_msg response;
+ int ret;
+
+ memset(&request, 0, sizeof(request));
+ request.command = WILCO_EC_COMMAND_KBBL;
+ request.subcmd = WILCO_KBBL_SUBCMD_GET_STATE;
+
+ ret = send_kbbl_msg(ec, &request, &response);
+ if (ret < 0)
+ return ret;
+
+ if (response.mode & WILCO_KBBL_MODE_FLAG_PWM)
+ return response.percent;
+
+ ret = set_kbbl(ec, WILCO_KBBL_DEFAULT_BRIGHTNESS);
+ if (ret < 0)
+ return ret;
+
+ return WILCO_KBBL_DEFAULT_BRIGHTNESS;
+}
+
+static int wilco_keyboard_leds_set(struct led_classdev *cdev,
+ enum led_brightness brightness)
+{
+ struct wilco_keyboard_leds *wkl =
+ container_of(cdev, struct wilco_keyboard_leds, keyboard);
+ return set_kbbl(wkl->ec, brightness);
+}
+
+int wilco_keyboard_leds_init(struct wilco_ec_device *ec)
+{
+ struct wilco_keyboard_leds *wkl;
+ bool leds_exist;
+ int ret;
+
+ ret = kbbl_exist(ec, &leds_exist);
+ if (ret < 0) {
+ dev_err(ec->dev,
+ "Failed checking keyboard LEDs support: %d", ret);
+ return ret;
+ }
+ if (!leds_exist)
+ return 0;
+
+ wkl = devm_kzalloc(ec->dev, sizeof(*wkl), GFP_KERNEL);
+ if (!wkl)
+ return -ENOMEM;
+
+ wkl->ec = ec;
+ wkl->keyboard.name = "platform::kbd_backlight";
+ wkl->keyboard.max_brightness = 100;
+ wkl->keyboard.flags = LED_CORE_SUSPENDRESUME;
+ wkl->keyboard.brightness_set_blocking = wilco_keyboard_leds_set;
+ ret = kbbl_init(ec);
+ if (ret < 0)
+ return ret;
+ wkl->keyboard.brightness = ret;
+
+ return devm_led_classdev_register(ec->dev, &wkl->keyboard);
+}
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