drivers/hwmon/surface_temp.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Thermal sensor subsystem driver for Surface System Aggregator Module (SSAM).
   4  *
   5  * Copyright (C) 2022-2023 Maximilian Luz <luzmaximilian@gmail.com>
   6  */
   7
   8 #include <linux/bitops.h>
   9 #include <linux/hwmon.h>
  10 #include <linux/kernel.h>
  11 #include <linux/module.h>
  12 #include <linux/types.h>
  13
  14 #include <linux/surface_aggregator/controller.h>
  15 #include <linux/surface_aggregator/device.h>
  16
  17 /* -- SAM interface. -------------------------------------------------------- */
  18
  19 /*
  20  * Available sensors are indicated by a 16-bit bitfield, where a 1 marks the
  21  * presence of a sensor. So we have at most 16 possible sensors/channels.
  22  */
  23 #define SSAM_TMP_SENSOR_MAX_COUNT       16
  24
  25 /*
  26  * All names observed so far are 6 characters long, but there's only
  27  * zeros after the name, so perhaps they can be longer. This number reflects
  28  * the maximum zero-padded space observed in the returned buffer.
  29  */
  30 #define SSAM_TMP_SENSOR_NAME_LENGTH     18
  31
  32 struct ssam_tmp_get_name_rsp {
  33         __le16 unknown1;
  34         char unknown2;
  35         char name[SSAM_TMP_SENSOR_NAME_LENGTH];
  36 } __packed;
  37
  38 static_assert(sizeof(struct ssam_tmp_get_name_rsp) == 21);
  39
  40 SSAM_DEFINE_SYNC_REQUEST_CL_R(__ssam_tmp_get_available_sensors, __le16, {
  41         .target_category = SSAM_SSH_TC_TMP,
  42         .command_id      = 0x04,
  43 });
  44
  45 SSAM_DEFINE_SYNC_REQUEST_MD_R(__ssam_tmp_get_temperature, __le16, {
  46         .target_category = SSAM_SSH_TC_TMP,
  47         .command_id      = 0x01,
  48 });
  49
  50 SSAM_DEFINE_SYNC_REQUEST_MD_R(__ssam_tmp_get_name, struct ssam_tmp_get_name_rsp, {
  51         .target_category = SSAM_SSH_TC_TMP,
  52         .command_id      = 0x0e,
  53 });
  54
  55 static int ssam_tmp_get_available_sensors(struct ssam_device *sdev, s16 *sensors)
  56 {
  57         __le16 sensors_le;
  58         int status;
  59
  60         status = __ssam_tmp_get_available_sensors(sdev, &sensors_le);
  61         if (status)
  62                 return status;
  63
  64         *sensors = le16_to_cpu(sensors_le);
  65         return 0;
  66 }
  67
  68 static int ssam_tmp_get_temperature(struct ssam_device *sdev, u8 iid, long *temperature)
  69 {
  70         __le16 temp_le;
  71         int status;
  72
  73         status = __ssam_tmp_get_temperature(sdev->ctrl, sdev->uid.target, iid, &temp_le);
  74         if (status)
  75                 return status;
  76
  77         /* Convert 1/10 °K to 1/1000 °C */
  78         *temperature = (le16_to_cpu(temp_le) - 2731) * 100L;
  79         return 0;
  80 }
  81
  82 static int ssam_tmp_get_name(struct ssam_device *sdev, u8 iid, char *buf, size_t buf_len)
  83 {
  84         struct ssam_tmp_get_name_rsp name_rsp;
  85         int status;
  86
  87         status =  __ssam_tmp_get_name(sdev->ctrl, sdev->uid.target, iid, &name_rsp);
  88         if (status)
  89                 return status;
  90
  91         /*
  92          * This should not fail unless the name in the returned struct is not
  93          * null-terminated or someone changed something in the struct
  94          * definitions above, since our buffer and struct have the same
  95          * capacity by design. So if this fails, log an error message. Since
  96          * the more likely cause is that the returned string isn't
  97          * null-terminated, we might have received garbage (as opposed to just
  98          * an incomplete string), so also fail the function.
  99          */
 100         status = strscpy(buf, name_rsp.name, buf_len);
 101         if (status < 0) {
 102                 dev_err(&sdev->dev, "received non-null-terminated sensor name string\n");
 103                 return status;
 104         }
 105
 106         return 0;
 107 }
 108
 109 /* -- Driver.---------------------------------------------------------------- */
 110
 111 struct ssam_temp {
 112         struct ssam_device *sdev;
 113         s16 sensors;
 114         char names[SSAM_TMP_SENSOR_MAX_COUNT][SSAM_TMP_SENSOR_NAME_LENGTH];
 115 };
 116
 117 static umode_t ssam_temp_hwmon_is_visible(const void *data,
 118                                           enum hwmon_sensor_types type,
 119                                           u32 attr, int channel)
 120 {
 121         const struct ssam_temp *ssam_temp = data;
 122
 123         if (!(ssam_temp->sensors & BIT(channel)))
 124                 return 0;
 125
 126         return 0444;
 127 }
 128
 129 static int ssam_temp_hwmon_read(struct device *dev,
 130                                 enum hwmon_sensor_types type,
 131                                 u32 attr, int channel, long *value)
 132 {
 133         const struct ssam_temp *ssam_temp = dev_get_drvdata(dev);
 134
 135         return ssam_tmp_get_temperature(ssam_temp->sdev, channel + 1, value);
 136 }
 137
 138 static int ssam_temp_hwmon_read_string(struct device *dev,
 139                                        enum hwmon_sensor_types type,
 140                                        u32 attr, int channel, const char **str)
 141 {
 142         const struct ssam_temp *ssam_temp = dev_get_drvdata(dev);
 143
 144         *str = ssam_temp->names[channel];
 145         return 0;
 146 }
 147
 148 static const struct hwmon_channel_info * const ssam_temp_hwmon_info[] = {
 149         HWMON_CHANNEL_INFO(chip,
 150                            HWMON_C_REGISTER_TZ),
 151         HWMON_CHANNEL_INFO(temp,
 152                            HWMON_T_INPUT | HWMON_T_LABEL,
 153                            HWMON_T_INPUT | HWMON_T_LABEL,
 154                            HWMON_T_INPUT | HWMON_T_LABEL,
 155                            HWMON_T_INPUT | HWMON_T_LABEL,
 156                            HWMON_T_INPUT | HWMON_T_LABEL,
 157                            HWMON_T_INPUT | HWMON_T_LABEL,
 158                            HWMON_T_INPUT | HWMON_T_LABEL,
 159                            HWMON_T_INPUT | HWMON_T_LABEL,
 160                            HWMON_T_INPUT | HWMON_T_LABEL,
 161                            HWMON_T_INPUT | HWMON_T_LABEL,
 162                            HWMON_T_INPUT | HWMON_T_LABEL,
 163                            HWMON_T_INPUT | HWMON_T_LABEL,
 164                            HWMON_T_INPUT | HWMON_T_LABEL,
 165                            HWMON_T_INPUT | HWMON_T_LABEL,
 166                            HWMON_T_INPUT | HWMON_T_LABEL,
 167                            HWMON_T_INPUT | HWMON_T_LABEL),
 168         NULL
 169 };
 170
 171 static const struct hwmon_ops ssam_temp_hwmon_ops = {
 172         .is_visible = ssam_temp_hwmon_is_visible,
 173         .read = ssam_temp_hwmon_read,
 174         .read_string = ssam_temp_hwmon_read_string,
 175 };
 176
 177 static const struct hwmon_chip_info ssam_temp_hwmon_chip_info = {
 178         .ops = &ssam_temp_hwmon_ops,
 179         .info = ssam_temp_hwmon_info,
 180 };
 181
 182 static int ssam_temp_probe(struct ssam_device *sdev)
 183 {
 184         struct ssam_temp *ssam_temp;
 185         struct device *hwmon_dev;
 186         s16 sensors;
 187         int channel;
 188         int status;
 189
 190         status = ssam_tmp_get_available_sensors(sdev, &sensors);
 191         if (status)
 192                 return status;
 193
 194         ssam_temp = devm_kzalloc(&sdev->dev, sizeof(*ssam_temp), GFP_KERNEL);
 195         if (!ssam_temp)
 196                 return -ENOMEM;
 197
 198         ssam_temp->sdev = sdev;
 199         ssam_temp->sensors = sensors;
 200
 201         /* Retrieve the name for each available sensor. */
 202         for (channel = 0; channel < SSAM_TMP_SENSOR_MAX_COUNT; channel++) {
 203                 if (!(sensors & BIT(channel)))
 204                         continue;
 205
 206                 status = ssam_tmp_get_name(sdev, channel + 1, ssam_temp->names[channel],
 207                                            SSAM_TMP_SENSOR_NAME_LENGTH);
 208                 if (status)
 209                         return status;
 210         }
 211
 212         hwmon_dev = devm_hwmon_device_register_with_info(&sdev->dev, "surface_thermal", ssam_temp,
 213                                                          &ssam_temp_hwmon_chip_info, NULL);
 214         return PTR_ERR_OR_ZERO(hwmon_dev);
 215 }
 216
 217 static const struct ssam_device_id ssam_temp_match[] = {
 218         { SSAM_SDEV(TMP, SAM, 0x00, 0x02) },
 219         { },
 220 };
 221 MODULE_DEVICE_TABLE(ssam, ssam_temp_match);
 222
 223 static struct ssam_device_driver ssam_temp = {
 224         .probe = ssam_temp_probe,
 225         .match_table = ssam_temp_match,
 226         .driver = {
 227                 .name = "surface_temp",
 228                 .probe_type = PROBE_PREFER_ASYNCHRONOUS,
 229         },
 230 };
 231 module_ssam_device_driver(ssam_temp);
 232
 233 MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
 234 MODULE_DESCRIPTION("Thermal sensor subsystem driver for Surface System Aggregator Module");
 235 MODULE_LICENSE("GPL");