--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * corsair-psu.c - Linux driver for Corsair power supplies with HID sensors interface
+ * Copyright (C) 2020 Wilken Gottwalt <wilken.gottwalt@posteo.net>
+ */
+
+#include <linux/completion.h>
+#include <linux/debugfs.h>
+#include <linux/errno.h>
+#include <linux/hid.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+/*
+ * Corsair protocol for PSUs
+ *
+ * message size = 64 bytes (request and response, little endian)
+ * request:
+ *     [length][command][param0][param1][paramX]...
+ * reply:
+ *     [echo of length][echo of command][data0][data1][dataX]...
+ *
+ *     - commands are byte sized opcodes
+ *     - length is the sum of all bytes of the commands/params
+ *     - the micro-controller of most of these PSUs support concatenation in the request and reply,
+ *       but it is better to not rely on this (it is also hard to parse)
+ *     - the driver uses raw events to be accessible from userspace (though this is not really
+ *       supported, it is just there for convenience, may be removed in the future)
+ *     - a reply always start with the length and command in the same order the request used it
+ *     - length of the reply data is specific to the command used
+ *     - some of the commands work on a rail and can be switched to a specific rail (0 = 12v,
+ *       1 = 5v, 2 = 3.3v)
+ *     - the format of the init command 0xFE is swapped length/command bytes
+ *     - parameter bytes amount and values are specific to the command (rail setting is the only
+ *       for now that uses non-zero values)
+ *     - there are much more commands, especially for configuring the device, but they are not
+ *       supported because a wrong command/length can lockup the micro-controller
+ *     - the driver supports debugfs for values not fitting into the hwmon class
+ *     - not every device class (HXi, RMi or AXi) supports all commands
+ *     - it is a pure sensors reading driver (will not support configuring)
+ */
+
+#define DRIVER_NAME            "corsair-psu"
+
+#define REPLY_SIZE             16 /* max length of a reply to a single command */
+#define CMD_BUFFER_SIZE                64
+#define CMD_TIMEOUT_MS         250
+#define SECONDS_PER_HOUR       (60 * 60)
+#define SECONDS_PER_DAY                (SECONDS_PER_HOUR * 24)
+
+#define PSU_CMD_SELECT_RAIL    0x00 /* expects length 2 */
+#define PSU_CMD_IN_VOLTS       0x88 /* the rest of the commands expect length 3 */
+#define PSU_CMD_IN_AMPS                0x89
+#define PSU_CMD_RAIL_OUT_VOLTS 0x8B
+#define PSU_CMD_RAIL_AMPS      0x8C
+#define PSU_CMD_TEMP0          0x8D
+#define PSU_CMD_TEMP1          0x8E
+#define PSU_CMD_FAN            0x90
+#define PSU_CMD_RAIL_WATTS     0x96
+#define PSU_CMD_VEND_STR       0x99
+#define PSU_CMD_PROD_STR       0x9A
+#define PSU_CMD_TOTAL_WATTS    0xEE
+#define PSU_CMD_TOTAL_UPTIME   0xD1
+#define PSU_CMD_UPTIME         0xD2
+#define PSU_CMD_INIT           0xFE
+
+#define L_IN_VOLTS             "v_in"
+#define L_OUT_VOLTS_12V                "v_out +12v"
+#define L_OUT_VOLTS_5V         "v_out +5v"
+#define L_OUT_VOLTS_3_3V       "v_out +3.3v"
+#define L_IN_AMPS              "curr in"
+#define L_AMPS_12V             "curr +12v"
+#define L_AMPS_5V              "curr +5v"
+#define L_AMPS_3_3V            "curr +3.3v"
+#define L_FAN                  "psu fan"
+#define L_TEMP0                        "vrm temp"
+#define L_TEMP1                        "case temp"
+#define L_WATTS                        "power total"
+#define L_WATTS_12V            "power +12v"
+#define L_WATTS_5V             "power +5v"
+#define L_WATTS_3_3V           "power +3.3v"
+
+static const char *const label_watts[] = {
+       L_WATTS,
+       L_WATTS_12V,
+       L_WATTS_5V,
+       L_WATTS_3_3V
+};
+
+static const char *const label_volts[] = {
+       L_IN_VOLTS,
+       L_OUT_VOLTS_12V,
+       L_OUT_VOLTS_5V,
+       L_OUT_VOLTS_3_3V
+};
+
+static const char *const label_amps[] = {
+       L_IN_AMPS,
+       L_AMPS_12V,
+       L_AMPS_5V,
+       L_AMPS_3_3V
+};
+
+struct corsairpsu_data {
+       struct hid_device *hdev;
+       struct device *hwmon_dev;
+       struct dentry *debugfs;
+       struct completion wait_completion;
+       struct mutex lock; /* for locking access to cmd_buffer */
+       u8 *cmd_buffer;
+       char vendor[REPLY_SIZE];
+       char product[REPLY_SIZE];
+};
+
+/* some values are SMBus LINEAR11 data which need a conversion */
+static int corsairpsu_linear11_to_int(const int val)
+{
+       int exp = (val & 0xFFFF) >> 0x0B;
+       int mant = val & 0x7FF;
+       int i;
+
+       if (exp > 0x0F)
+               exp -= 0x20;
+       if (mant > 0x3FF)
+               mant -= 0x800;
+       if ((mant & 0x01) == 1)
+               ++mant;
+       if (exp < 0) {
+               for (i = 0; i < -exp; ++i)
+                       mant /= 2;
+       } else {
+               for (i = 0; i < exp; ++i)
+                       mant *= 2;
+       }
+
+       return mant;
+}
+
+static int corsairpsu_usb_cmd(struct corsairpsu_data *priv, u8 p0, u8 p1, u8 p2, void *data)
+{
+       unsigned long time;
+       int ret;
+
+       memset(priv->cmd_buffer, 0, CMD_BUFFER_SIZE);
+       priv->cmd_buffer[0] = p0;
+       priv->cmd_buffer[1] = p1;
+       priv->cmd_buffer[2] = p2;
+
+       reinit_completion(&priv->wait_completion);
+
+       ret = hid_hw_output_report(priv->hdev, priv->cmd_buffer, CMD_BUFFER_SIZE);
+       if (ret < 0)
+               return ret;
+
+       time = wait_for_completion_timeout(&priv->wait_completion,
+                                          msecs_to_jiffies(CMD_TIMEOUT_MS));
+       if (!time)
+               return -ETIMEDOUT;
+
+       /*
+        * at the start of the reply is an echo of the send command/length in the same order it
+        * was send, not every command is supported on every device class, if a command is not
+        * supported, the length value in the reply is okay, but the command value is set to 0
+        */
+       if (p0 != priv->cmd_buffer[0] || p1 != priv->cmd_buffer[1])
+               return -EOPNOTSUPP;
+
+       if (data)
+               memcpy(data, priv->cmd_buffer + 2, REPLY_SIZE);
+
+       return 0;
+}
+
+static int corsairpsu_init(struct corsairpsu_data *priv)
+{
+       /*
+        * PSU_CMD_INIT uses swapped length/command and expects 2 parameter bytes, this command
+        * actually generates a reply, but we don't need it
+        */
+       return corsairpsu_usb_cmd(priv, PSU_CMD_INIT, 3, 0, NULL);
+}
+
+static int corsairpsu_fwinfo(struct corsairpsu_data *priv)
+{
+       int ret;
+
+       ret = corsairpsu_usb_cmd(priv, 3, PSU_CMD_VEND_STR, 0, priv->vendor);
+       if (ret < 0)
+               return ret;
+
+       ret = corsairpsu_usb_cmd(priv, 3, PSU_CMD_PROD_STR, 0, priv->product);
+       if (ret < 0)
+               return ret;
+
+       return 0;
+}
+
+static int corsairpsu_request(struct corsairpsu_data *priv, u8 cmd, u8 rail, void *data)
+{
+       int ret;
+
+       mutex_lock(&priv->lock);
+       switch (cmd) {
+       case PSU_CMD_RAIL_OUT_VOLTS:
+       case PSU_CMD_RAIL_AMPS:
+       case PSU_CMD_RAIL_WATTS:
+               ret = corsairpsu_usb_cmd(priv, 2, PSU_CMD_SELECT_RAIL, rail, NULL);
+               if (ret < 0)
+                       goto cmd_fail;
+               break;
+       default:
+               break;
+       }
+
+       ret = corsairpsu_usb_cmd(priv, 3, cmd, 0, data);
+
+cmd_fail:
+       mutex_unlock(&priv->lock);
+       return ret;
+}
+
+static int corsairpsu_get_value(struct corsairpsu_data *priv, u8 cmd, u8 rail, long *val)
+{
+       u8 data[REPLY_SIZE];
+       long tmp;
+       int ret;
+
+       ret = corsairpsu_request(priv, cmd, rail, data);
+       if (ret < 0)
+               return ret;
+
+       /*
+        * the biggest value here comes from the uptime command and to exceed MAXINT total uptime
+        * needs to be about 68 years, the rest are u16 values and the biggest value coming out of
+        * the LINEAR11 conversion are the watts values which are about 1200 for the strongest psu
+        * supported (HX1200i)
+        */
+       tmp = (data[3] << 24) + (data[2] << 16) + (data[1] << 8) + data[0];
+       switch (cmd) {
+       case PSU_CMD_IN_VOLTS:
+       case PSU_CMD_IN_AMPS:
+       case PSU_CMD_RAIL_OUT_VOLTS:
+       case PSU_CMD_RAIL_AMPS:
+       case PSU_CMD_TEMP0:
+       case PSU_CMD_TEMP1:
+               *val = corsairpsu_linear11_to_int(tmp & 0xFFFF) * 1000;
+               break;
+       case PSU_CMD_FAN:
+               /*
+                * this value is best guess, so the calculated value could be wrong, it is hard
+                * to ge the fan to spin in these semi-passive power supplies, which need a
+                * quite high load to do so
+                */
+               *val = ((tmp & 0xFF) << 8) + ((tmp >> 8) & 0xFF);
+               break;
+       case PSU_CMD_RAIL_WATTS:
+       case PSU_CMD_TOTAL_WATTS:
+               *val = corsairpsu_linear11_to_int(tmp & 0xFFFF) * 1000000;
+               break;
+       case PSU_CMD_TOTAL_UPTIME:
+       case PSU_CMD_UPTIME:
+               *val = tmp;
+               break;
+       default:
+               ret = -EOPNOTSUPP;
+               break;
+       }
+
+       return ret;
+}
+
+static umode_t corsairpsu_hwmon_ops_is_visible(const void *data, enum hwmon_sensor_types type,
+                                              u32 attr, int channel)
+{
+       if (type == hwmon_temp && (attr == hwmon_temp_input || attr == hwmon_temp_label))
+               return 0444;
+       else if (type == hwmon_fan && (attr == hwmon_fan_input || attr == hwmon_fan_label))
+               return 0444;
+       else if (type == hwmon_power && (attr == hwmon_power_input || attr == hwmon_power_label))
+               return 0444;
+       else if (type == hwmon_in && (attr == hwmon_in_input || attr == hwmon_in_label))
+               return 0444;
+       else if (type == hwmon_curr && (attr == hwmon_curr_input || attr == hwmon_curr_label))
+               return 0444;
+
+       return 0;
+}
+
+static int corsairpsu_hwmon_ops_read(struct device *dev, enum hwmon_sensor_types type, u32 attr,
+                                    int channel, long *val)
+{
+       struct corsairpsu_data *priv = dev_get_drvdata(dev);
+       int ret;
+
+       if (type == hwmon_temp && attr == hwmon_temp_input && channel < 2) {
+               ret = corsairpsu_get_value(priv, channel ? PSU_CMD_TEMP1 : PSU_CMD_TEMP0, channel,
+                                          val);
+       } else if (type == hwmon_fan && attr == hwmon_fan_input) {
+               ret = corsairpsu_get_value(priv, PSU_CMD_FAN, 0, val);
+       } else if (type == hwmon_power && attr == hwmon_power_input) {
+               switch (channel) {
+               case 0:
+                       ret = corsairpsu_get_value(priv, PSU_CMD_TOTAL_WATTS, 0, val);
+                       break;
+               case 1 ... 3:
+                       ret = corsairpsu_get_value(priv, PSU_CMD_RAIL_WATTS, channel - 1, val);
+                       break;
+               default:
+                       return -EOPNOTSUPP;
+               }
+       } else if (type == hwmon_in && attr == hwmon_in_input) {
+               switch (channel) {
+               case 0:
+                       ret = corsairpsu_get_value(priv, PSU_CMD_IN_VOLTS, 0, val);
+                       break;
+               case 1 ... 3:
+                       ret = corsairpsu_get_value(priv, PSU_CMD_RAIL_OUT_VOLTS, channel - 1, val);
+                       break;
+               default:
+                       return -EOPNOTSUPP;
+               }
+       } else if (type == hwmon_curr && attr == hwmon_curr_input) {
+               switch (channel) {
+               case 0:
+                       ret = corsairpsu_get_value(priv, PSU_CMD_IN_AMPS, 0, val);
+                       break;
+               case 1 ... 3:
+                       ret = corsairpsu_get_value(priv, PSU_CMD_RAIL_AMPS, channel - 1, val);
+                       break;
+               default:
+                       return -EOPNOTSUPP;
+               }
+       } else {
+               return -EOPNOTSUPP;
+       }
+
+       if (ret < 0)
+               return ret;
+
+       return 0;
+}
+
+static int corsairpsu_hwmon_ops_read_string(struct device *dev, enum hwmon_sensor_types type,
+                                           u32 attr, int channel, const char **str)
+{
+       if (type == hwmon_temp && attr == hwmon_temp_label) {
+               *str = channel ? L_TEMP1 : L_TEMP0;
+               return 0;
+       } else if (type == hwmon_fan && attr == hwmon_fan_label) {
+               *str = L_FAN;
+               return 0;
+       } else if (type == hwmon_power && attr == hwmon_power_label && channel < 4) {
+               *str = label_watts[channel];
+               return 0;
+       } else if (type == hwmon_in && attr == hwmon_in_label && channel < 4) {
+               *str = label_volts[channel];
+               return 0;
+       } else if (type == hwmon_curr && attr == hwmon_curr_label && channel < 4) {
+               *str = label_amps[channel];
+               return 0;
+       }
+
+       return -EOPNOTSUPP;
+}
+
+static const struct hwmon_ops corsairpsu_hwmon_ops = {
+       .is_visible     = corsairpsu_hwmon_ops_is_visible,
+       .read           = corsairpsu_hwmon_ops_read,
+       .read_string    = corsairpsu_hwmon_ops_read_string,
+};
+
+static const struct hwmon_channel_info *corsairpsu_info[] = {
+       HWMON_CHANNEL_INFO(chip,
+                          HWMON_C_REGISTER_TZ),
+       HWMON_CHANNEL_INFO(temp,
+                          HWMON_T_INPUT | HWMON_T_LABEL,
+                          HWMON_T_INPUT | HWMON_T_LABEL),
+       HWMON_CHANNEL_INFO(fan,
+                          HWMON_F_INPUT | HWMON_F_LABEL),
+       HWMON_CHANNEL_INFO(power,
+                          HWMON_P_INPUT | HWMON_P_LABEL,
+                          HWMON_P_INPUT | HWMON_P_LABEL,
+                          HWMON_P_INPUT | HWMON_P_LABEL,
+                          HWMON_P_INPUT | HWMON_P_LABEL),
+       HWMON_CHANNEL_INFO(in,
+                          HWMON_I_INPUT | HWMON_I_LABEL,
+                          HWMON_I_INPUT | HWMON_I_LABEL,
+                          HWMON_I_INPUT | HWMON_I_LABEL,
+                          HWMON_I_INPUT | HWMON_I_LABEL),
+       HWMON_CHANNEL_INFO(curr,
+                          HWMON_C_INPUT | HWMON_C_LABEL,
+                          HWMON_C_INPUT | HWMON_C_LABEL,
+                          HWMON_C_INPUT | HWMON_C_LABEL,
+                          HWMON_C_INPUT | HWMON_C_LABEL),
+       NULL
+};
+
+static const struct hwmon_chip_info corsairpsu_chip_info = {
+       .ops    = &corsairpsu_hwmon_ops,
+       .info   = corsairpsu_info,
+};
+
+#ifdef CONFIG_DEBUG_FS
+
+static void print_uptime(struct seq_file *seqf, u8 cmd)
+{
+       struct corsairpsu_data *priv = seqf->private;
+       long val;
+       int ret;
+
+       ret = corsairpsu_get_value(priv, cmd, 0, &val);
+       if (ret < 0) {
+               seq_puts(seqf, "N/A\n");
+               return;
+       }
+
+       if (val > SECONDS_PER_DAY) {
+               seq_printf(seqf, "%ld day(s), %02ld:%02ld:%02ld\n", val / SECONDS_PER_DAY,
+                          val % SECONDS_PER_DAY / SECONDS_PER_HOUR, val % SECONDS_PER_HOUR / 60,
+                          val % 60);
+               return;
+       }
+
+       seq_printf(seqf, "%02ld:%02ld:%02ld\n", val % SECONDS_PER_DAY / SECONDS_PER_HOUR,
+                  val % SECONDS_PER_HOUR / 60, val % 60);
+}
+
+static int uptime_show(struct seq_file *seqf, void *unused)
+{
+       print_uptime(seqf, PSU_CMD_UPTIME);
+
+       return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(uptime);
+
+static int uptime_total_show(struct seq_file *seqf, void *unused)
+{
+       print_uptime(seqf, PSU_CMD_TOTAL_UPTIME);
+
+       return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(uptime_total);
+
+static int vendor_show(struct seq_file *seqf, void *unused)
+{
+       struct corsairpsu_data *priv = seqf->private;
+
+       seq_printf(seqf, "%s\n", priv->vendor);
+
+       return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(vendor);
+
+static int product_show(struct seq_file *seqf, void *unused)
+{
+       struct corsairpsu_data *priv = seqf->private;
+
+       seq_printf(seqf, "%s\n", priv->product);
+
+       return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(product);
+
+static void corsairpsu_debugfs_init(struct corsairpsu_data *priv)
+{
+       char name[32];
+
+       scnprintf(name, sizeof(name), "%s-%s", DRIVER_NAME, dev_name(&priv->hdev->dev));
+
+       priv->debugfs = debugfs_create_dir(name, NULL);
+       debugfs_create_file("uptime", 0444, priv->debugfs, priv, &uptime_fops);
+       debugfs_create_file("uptime_total", 0444, priv->debugfs, priv, &uptime_total_fops);
+       debugfs_create_file("vendor", 0444, priv->debugfs, priv, &vendor_fops);
+       debugfs_create_file("product", 0444, priv->debugfs, priv, &product_fops);
+}
+
+#else
+
+static void corsairpsu_debugfs_init(struct corsairpsu_data *priv)
+{
+}
+
+#endif
+
+static int corsairpsu_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+       struct corsairpsu_data *priv;
+       int ret;
+
+       priv = devm_kzalloc(&hdev->dev, sizeof(struct corsairpsu_data), GFP_KERNEL);
+       if (!priv)
+               return -ENOMEM;
+
+       priv->cmd_buffer = devm_kmalloc(&hdev->dev, CMD_BUFFER_SIZE, GFP_KERNEL);
+       if (!priv->cmd_buffer)
+               return -ENOMEM;
+
+       ret = hid_parse(hdev);
+       if (ret)
+               return ret;
+
+       ret = hid_hw_start(hdev, HID_CONNECT_HIDRAW);
+       if (ret)
+               return ret;
+
+       ret = hid_hw_open(hdev);
+       if (ret)
+               goto fail_and_stop;
+
+       priv->hdev = hdev;
+       hid_set_drvdata(hdev, priv);
+       mutex_init(&priv->lock);
+       init_completion(&priv->wait_completion);
+
+       hid_device_io_start(hdev);
+
+       ret = corsairpsu_init(priv);
+       if (ret < 0) {
+               dev_err(&hdev->dev, "unable to initialize device (%d)\n", ret);
+               goto fail_and_stop;
+       }
+
+       ret = corsairpsu_fwinfo(priv);
+       if (ret < 0) {
+               dev_err(&hdev->dev, "unable to query firmware (%d)\n", ret);
+               goto fail_and_stop;
+       }
+
+       priv->hwmon_dev = hwmon_device_register_with_info(&hdev->dev, "corsairpsu", priv,
+                                                         &corsairpsu_chip_info, 0);
+
+       if (IS_ERR(priv->hwmon_dev)) {
+               ret = PTR_ERR(priv->hwmon_dev);
+               goto fail_and_close;
+       }
+
+       corsairpsu_debugfs_init(priv);
+
+       return 0;
+
+fail_and_close:
+       hid_hw_close(hdev);
+fail_and_stop:
+       hid_hw_stop(hdev);
+       return ret;
+}
+
+static void corsairpsu_remove(struct hid_device *hdev)
+{
+       struct corsairpsu_data *priv = hid_get_drvdata(hdev);
+
+       debugfs_remove_recursive(priv->debugfs);
+       hwmon_device_unregister(priv->hwmon_dev);
+       hid_hw_close(hdev);
+       hid_hw_stop(hdev);
+}
+
+static int corsairpsu_raw_event(struct hid_device *hdev, struct hid_report *report, u8 *data,
+                               int size)
+{
+       struct corsairpsu_data *priv = hid_get_drvdata(hdev);
+
+       if (completion_done(&priv->wait_completion))
+               return 0;
+
+       memcpy(priv->cmd_buffer, data, min(CMD_BUFFER_SIZE, size));
+       complete(&priv->wait_completion);
+
+       return 0;
+}
+
+static const struct hid_device_id corsairpsu_idtable[] = {
+       { HID_USB_DEVICE(0x1b1c, 0x1c03) }, /* Corsair HX550i */
+       { HID_USB_DEVICE(0x1b1c, 0x1c04) }, /* Corsair HX650i */
+       { HID_USB_DEVICE(0x1b1c, 0x1c05) }, /* Corsair HX750i */
+       { HID_USB_DEVICE(0x1b1c, 0x1c06) }, /* Corsair HX850i */
+       { HID_USB_DEVICE(0x1b1c, 0x1c07) }, /* Corsair HX1000i */
+       { HID_USB_DEVICE(0x1b1c, 0x1c08) }, /* Corsair HX1200i */
+       { HID_USB_DEVICE(0x1b1c, 0x1c09) }, /* Corsair RM550i */
+       { HID_USB_DEVICE(0x1b1c, 0x1c0a) }, /* Corsair RM650i */
+       { HID_USB_DEVICE(0x1b1c, 0x1c0b) }, /* Corsair RM750i */
+       { HID_USB_DEVICE(0x1b1c, 0x1c0c) }, /* Corsair RM850i */
+       { HID_USB_DEVICE(0x1b1c, 0x1c0d) }, /* Corsair RM1000i */
+       { },
+};
+MODULE_DEVICE_TABLE(hid, corsairpsu_idtable);
+
+static struct hid_driver corsairpsu_driver = {
+       .name           = DRIVER_NAME,
+       .id_table       = corsairpsu_idtable,
+       .probe          = corsairpsu_probe,
+       .remove         = corsairpsu_remove,
+       .raw_event      = corsairpsu_raw_event,
+};
+module_hid_driver(corsairpsu_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Wilken Gottwalt <wilken.gottwalt@posteo.net>");
+MODULE_DESCRIPTION("Linux driver for Corsair power supplies with HID sensors interface");