drivers/platform/chrome/wilco_ec/keyboard_leds.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Keyboard backlight LED driver for the Wilco Embedded Controller
   4  *
   5  * Copyright 2019 Google LLC
   6  *
   7  * Since the EC will never change the backlight level of its own accord,
   8  * we don't need to implement a brightness_get() method.
   9  */
  10
  11 #include <linux/device.h>
  12 #include <linux/kernel.h>
  13 #include <linux/leds.h>
  14 #include <linux/platform_data/wilco-ec.h>
  15 #include <linux/slab.h>
  16
  17 #define WILCO_EC_COMMAND_KBBL           0x75
  18 #define WILCO_KBBL_MODE_FLAG_PWM        BIT(1)  /* Set brightness by percent. */
  19 #define WILCO_KBBL_DEFAULT_BRIGHTNESS   0
  20
  21 struct wilco_keyboard_leds {
  22         struct wilco_ec_device *ec;
  23         struct led_classdev keyboard;
  24 };
  25
  26 enum wilco_kbbl_subcommand {
  27         WILCO_KBBL_SUBCMD_GET_FEATURES = 0x00,
  28         WILCO_KBBL_SUBCMD_GET_STATE    = 0x01,
  29         WILCO_KBBL_SUBCMD_SET_STATE    = 0x02,
  30 };
  31
  32 /**
  33  * struct wilco_keyboard_leds_msg - Message to/from EC for keyboard LED control.
  34  * @command: Always WILCO_EC_COMMAND_KBBL.
  35  * @status: Set by EC to 0 on success, 0xFF on failure.
  36  * @subcmd: One of enum wilco_kbbl_subcommand.
  37  * @reserved3: Should be 0.
  38  * @mode: Bit flags for used mode, we want to use WILCO_KBBL_MODE_FLAG_PWM.
  39  * @reserved5to8: Should be 0.
  40  * @percent: Brightness in 0-100. Only meaningful in PWM mode.
  41  * @reserved10to15: Should be 0.
  42  */
  43 struct wilco_keyboard_leds_msg {
  44         u8 command;
  45         u8 status;
  46         u8 subcmd;
  47         u8 reserved3;
  48         u8 mode;
  49         u8 reserved5to8[4];
  50         u8 percent;
  51         u8 reserved10to15[6];
  52 } __packed;
  53
  54 /* Send a request, get a response, and check that the response is good. */
  55 static int send_kbbl_msg(struct wilco_ec_device *ec,
  56                          struct wilco_keyboard_leds_msg *request,
  57                          struct wilco_keyboard_leds_msg *response)
  58 {
  59         struct wilco_ec_message msg;
  60         int ret;
  61
  62         memset(&msg, 0, sizeof(msg));
  63         msg.type = WILCO_EC_MSG_LEGACY;
  64         msg.request_data = request;
  65         msg.request_size = sizeof(*request);
  66         msg.response_data = response;
  67         msg.response_size = sizeof(*response);
  68
  69         ret = wilco_ec_mailbox(ec, &msg);
  70         if (ret < 0) {
  71                 dev_err(ec->dev,
  72                         "Failed sending keyboard LEDs command: %d", ret);
  73                 return ret;
  74         }
  75
  76         return 0;
  77 }
  78
  79 static int set_kbbl(struct wilco_ec_device *ec, enum led_brightness brightness)
  80 {
  81         struct wilco_keyboard_leds_msg request;
  82         struct wilco_keyboard_leds_msg response;
  83         int ret;
  84
  85         memset(&request, 0, sizeof(request));
  86         request.command = WILCO_EC_COMMAND_KBBL;
  87         request.subcmd  = WILCO_KBBL_SUBCMD_SET_STATE;
  88         request.mode    = WILCO_KBBL_MODE_FLAG_PWM;
  89         request.percent = brightness;
  90
  91         ret = send_kbbl_msg(ec, &request, &response);
  92         if (ret < 0)
  93                 return ret;
  94
  95         if (response.status) {
  96                 dev_err(ec->dev,
  97                         "EC reported failure sending keyboard LEDs command: %d",
  98                         response.status);
  99                 return -EIO;
 100         }
 101
 102         return 0;
 103 }
 104
 105 static int kbbl_exist(struct wilco_ec_device *ec, bool *exists)
 106 {
 107         struct wilco_keyboard_leds_msg request;
 108         struct wilco_keyboard_leds_msg response;
 109         int ret;
 110
 111         memset(&request, 0, sizeof(request));
 112         request.command = WILCO_EC_COMMAND_KBBL;
 113         request.subcmd  = WILCO_KBBL_SUBCMD_GET_FEATURES;
 114
 115         ret = send_kbbl_msg(ec, &request, &response);
 116         if (ret < 0)
 117                 return ret;
 118
 119         *exists = response.status != 0xFF;
 120
 121         return 0;
 122 }
 123
 124 /**
 125  * kbbl_init() - Initialize the state of the keyboard backlight.
 126  * @ec: EC device to talk to.
 127  *
 128  * Gets the current brightness, ensuring that the BIOS already initialized the
 129  * backlight to PWM mode. If not in PWM mode, then the current brightness is
 130  * meaningless, so set the brightness to WILCO_KBBL_DEFAULT_BRIGHTNESS.
 131  *
 132  * Return: Final brightness of the keyboard, or negative error code on failure.
 133  */
 134 static int kbbl_init(struct wilco_ec_device *ec)
 135 {
 136         struct wilco_keyboard_leds_msg request;
 137         struct wilco_keyboard_leds_msg response;
 138         int ret;
 139
 140         memset(&request, 0, sizeof(request));
 141         request.command = WILCO_EC_COMMAND_KBBL;
 142         request.subcmd  = WILCO_KBBL_SUBCMD_GET_STATE;
 143
 144         ret = send_kbbl_msg(ec, &request, &response);
 145         if (ret < 0)
 146                 return ret;
 147
 148         if (response.status) {
 149                 dev_err(ec->dev,
 150                         "EC reported failure sending keyboard LEDs command: %d",
 151                         response.status);
 152                 return -EIO;
 153         }
 154
 155         if (response.mode & WILCO_KBBL_MODE_FLAG_PWM)
 156                 return response.percent;
 157
 158         ret = set_kbbl(ec, WILCO_KBBL_DEFAULT_BRIGHTNESS);
 159         if (ret < 0)
 160                 return ret;
 161
 162         return WILCO_KBBL_DEFAULT_BRIGHTNESS;
 163 }
 164
 165 static int wilco_keyboard_leds_set(struct led_classdev *cdev,
 166                                    enum led_brightness brightness)
 167 {
 168         struct wilco_keyboard_leds *wkl =
 169                 container_of(cdev, struct wilco_keyboard_leds, keyboard);
 170         return set_kbbl(wkl->ec, brightness);
 171 }
 172
 173 int wilco_keyboard_leds_init(struct wilco_ec_device *ec)
 174 {
 175         struct wilco_keyboard_leds *wkl;
 176         bool leds_exist;
 177         int ret;
 178
 179         ret = kbbl_exist(ec, &leds_exist);
 180         if (ret < 0) {
 181                 dev_err(ec->dev,
 182                         "Failed checking keyboard LEDs support: %d", ret);
 183                 return ret;
 184         }
 185         if (!leds_exist)
 186                 return 0;
 187
 188         wkl = devm_kzalloc(ec->dev, sizeof(*wkl), GFP_KERNEL);
 189         if (!wkl)
 190                 return -ENOMEM;
 191
 192         wkl->ec = ec;
 193         wkl->keyboard.name = "platform::kbd_backlight";
 194         wkl->keyboard.max_brightness = 100;
 195         wkl->keyboard.flags = LED_CORE_SUSPENDRESUME;
 196         wkl->keyboard.brightness_set_blocking = wilco_keyboard_leds_set;
 197         ret = kbbl_init(ec);
 198         if (ret < 0)
 199                 return ret;
 200         wkl->keyboard.brightness = ret;
 201
 202         return devm_led_classdev_register(ec->dev, &wkl->keyboard);
 203 }