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
 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 <luzmaximilian@gmail.com>");
234MODULE_DESCRIPTION("Thermal sensor subsystem driver for Surface System Aggregator Module");
235MODULE_LICENSE("GPL");