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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 <[email protected]>
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
32struct ssam_tmp_get_name_rsp {
33 __le16 unknown1;
34 char unknown2;
35 char name[SSAM_TMP_SENSOR_NAME_LENGTH];
36} __packed;
37
38static_assert(sizeof(struct ssam_tmp_get_name_rsp) == 21);
39
40SSAM_DEFINE_SYNC_REQUEST_CL_R(__ssam_tmp_get_available_sensors, __le16, {
41 .target_category = SSAM_SSH_TC_TMP,
42 .command_id = 0x04,
43});
44
45SSAM_DEFINE_SYNC_REQUEST_MD_R(__ssam_tmp_get_temperature, __le16, {
46 .target_category = SSAM_SSH_TC_TMP,
47 .command_id = 0x01,
48});
49
50SSAM_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
55static 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
68static 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
82static 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
111struct 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
117static 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
129static 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
138static 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
148static 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
171static 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
177static const struct hwmon_chip_info ssam_temp_hwmon_chip_info = {
178 .ops = &ssam_temp_hwmon_ops,
179 .info = ssam_temp_hwmon_info,
180};
181
182static 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
217static const struct ssam_device_id ssam_temp_match[] = {
218 { SSAM_SDEV(TMP, SAM, 0x00, 0x02) },
219 { },
220};
221MODULE_DEVICE_TABLE(ssam, ssam_temp_match);
222
223static 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};
231module_ssam_device_driver(ssam_temp);
232
233MODULE_AUTHOR("Maximilian Luz <[email protected]>");
234MODULE_DESCRIPTION("Thermal sensor subsystem driver for Surface System Aggregator Module");
235MODULE_LICENSE("GPL");